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avcodec.h (108272B)

---

/*
* copyright (c) 2001 Fabrice Bellard
*
* This file is part of FFmpeg.
*
* FFmpeg is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* FFmpeg is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/

#ifndef AVCODEC_AVCODEC_H
#define AVCODEC_AVCODEC_H

/**
* @file
* @ingroup libavc
* Libavcodec external API header
*/

#include "libavutil/samplefmt.h"
#include "libavutil/attributes.h"
#include "libavutil/avutil.h"
#include "libavutil/buffer.h"
#include "libavutil/channel_layout.h"
#include "libavutil/dict.h"
#include "libavutil/frame.h"
#include "libavutil/log.h"
#include "libavutil/pixfmt.h"
#include "libavutil/rational.h"

#include "codec.h"
#include "codec_id.h"
#include "defs.h"
#include "packet.h"
#include "version_major.h"
#ifndef HAVE_AV_CONFIG_H
/* When included as part of the ffmpeg build, only include the major version
* to avoid unnecessary rebuilds. When included externally, keep including
* the full version information. */
#  include "version.h"

#  include "codec_desc.h"
#  include "codec_par.h"
#endif

struct AVCodecParameters;

/**
* @defgroup libavc libavcodec
* Encoding/Decoding Library
*
* @{
*
* @defgroup lavc_decoding Decoding
* @{
* @}
*
* @defgroup lavc_encoding Encoding
* @{
* @}
*
* @defgroup lavc_codec Codecs
* @{
* @defgroup lavc_codec_native Native Codecs
* @{
* @}
* @defgroup lavc_codec_wrappers External library wrappers
* @{
* @}
* @defgroup lavc_codec_hwaccel Hardware Accelerators bridge
* @{
* @}
* @}
* @defgroup lavc_internal Internal
* @{
* @}
* @}
*/

/**
* @ingroup libavc
* @defgroup lavc_encdec send/receive encoding and decoding API overview
* @{
*
* The avcodec_send_packet()/avcodec_receive_frame()/avcodec_send_frame()/
* avcodec_receive_packet() functions provide an encode/decode API, which
* decouples input and output.
*
* The API is very similar for encoding/decoding and audio/video, and works as
* follows:
* - Set up and open the AVCodecContext as usual.
* - Send valid input:
*   - For decoding, call avcodec_send_packet() to give the decoder raw
*     compressed data in an AVPacket.
*   - For encoding, call avcodec_send_frame() to give the encoder an AVFrame
*     containing uncompressed audio or video.
*
*   In both cases, it is recommended that AVPackets and AVFrames are
*   refcounted, or libavcodec might have to copy the input data. (libavformat
*   always returns refcounted AVPackets, and av_frame_get_buffer() allocates
*   refcounted AVFrames.)
* - Receive output in a loop. Periodically call one of the avcodec_receive_*()
*   functions and process their output:
*   - For decoding, call avcodec_receive_frame(). On success, it will return
*     an AVFrame containing uncompressed audio or video data.
*   - For encoding, call avcodec_receive_packet(). On success, it will return
*     an AVPacket with a compressed frame.
*
*   Repeat this call until it returns AVERROR(EAGAIN) or an error. The
*   AVERROR(EAGAIN) return value means that new input data is required to
*   return new output. In this case, continue with sending input. For each
*   input frame/packet, the codec will typically return 1 output frame/packet,
*   but it can also be 0 or more than 1.
*
* At the beginning of decoding or encoding, the codec might accept multiple
* input frames/packets without returning a frame, until its internal buffers
* are filled. This situation is handled transparently if you follow the steps
* outlined above.
*
* In theory, sending input can result in EAGAIN - this should happen only if
* not all output was received. You can use this to structure alternative decode
* or encode loops other than the one suggested above. For example, you could
* try sending new input on each iteration, and try to receive output if that
* returns EAGAIN.
*
* End of stream situations. These require "flushing" (aka draining) the codec,
* as the codec might buffer multiple frames or packets internally for
* performance or out of necessity (consider B-frames).
* This is handled as follows:
* - Instead of valid input, send NULL to the avcodec_send_packet() (decoding)
*   or avcodec_send_frame() (encoding) functions. This will enter draining
*   mode.
* - Call avcodec_receive_frame() (decoding) or avcodec_receive_packet()
*   (encoding) in a loop until AVERROR_EOF is returned. The functions will
*   not return AVERROR(EAGAIN), unless you forgot to enter draining mode.
* - Before decoding can be resumed again, the codec has to be reset with
*   avcodec_flush_buffers().
*
* Using the API as outlined above is highly recommended. But it is also
* possible to call functions outside of this rigid schema. For example, you can
* call avcodec_send_packet() repeatedly without calling
* avcodec_receive_frame(). In this case, avcodec_send_packet() will succeed
* until the codec's internal buffer has been filled up (which is typically of
* size 1 per output frame, after initial input), and then reject input with
* AVERROR(EAGAIN). Once it starts rejecting input, you have no choice but to
* read at least some output.
*
* Not all codecs will follow a rigid and predictable dataflow; the only
* guarantee is that an AVERROR(EAGAIN) return value on a send/receive call on
* one end implies that a receive/send call on the other end will succeed, or
* at least will not fail with AVERROR(EAGAIN). In general, no codec will
* permit unlimited buffering of input or output.
*
* A codec is not allowed to return AVERROR(EAGAIN) for both sending and
* receiving. This would be an invalid state, which could put the codec user
* into an endless loop. The API has no concept of time either: it cannot happen
* that trying to do avcodec_send_packet() results in AVERROR(EAGAIN), but a
* repeated call 1 second later accepts the packet (with no other receive/flush
* API calls involved). The API is a strict state machine, and the passage of
* time is not supposed to influence it. Some timing-dependent behavior might
* still be deemed acceptable in certain cases. But it must never result in both
* send/receive returning EAGAIN at the same time at any point. It must also
* absolutely be avoided that the current state is "unstable" and can
* "flip-flop" between the send/receive APIs allowing progress. For example,
* it's not allowed that the codec randomly decides that it actually wants to
* consume a packet now instead of returning a frame, after it just returned
* AVERROR(EAGAIN) on an avcodec_send_packet() call.
* @}
*/

/**
* @defgroup lavc_core Core functions/structures.
* @ingroup libavc
*
* Basic definitions, functions for querying libavcodec capabilities,
* allocating core structures, etc.
* @{
*/

#if FF_API_BUFFER_MIN_SIZE
/**
* @ingroup lavc_encoding
* minimum encoding buffer size
* Used to avoid some checks during header writing.
* @deprecated Unused: avcodec_receive_packet() does not work
*             with preallocated packet buffers.
*/
#  define AV_INPUT_BUFFER_MIN_SIZE 16384
#endif

/**
* @ingroup lavc_encoding
*/
typedef struct RcOverride {
 int start_frame;
 int end_frame;
 int qscale;  // If this is 0 then quality_factor will be used instead.
 float quality_factor;
} RcOverride;

/* encoding support
  These flags can be passed in AVCodecContext.flags before initialization.
  Note: Not everything is supported yet.
*/

/**
* Allow decoders to produce frames with data planes that are not aligned
* to CPU requirements (e.g. due to cropping).
*/
#define AV_CODEC_FLAG_UNALIGNED (1 << 0)
/**
* Use fixed qscale.
*/
#define AV_CODEC_FLAG_QSCALE (1 << 1)
/**
* 4 MV per MB allowed / advanced prediction for H.263.
*/
#define AV_CODEC_FLAG_4MV (1 << 2)
/**
* Output even those frames that might be corrupted.
*/
#define AV_CODEC_FLAG_OUTPUT_CORRUPT (1 << 3)
/**
* Use qpel MC.
*/
#define AV_CODEC_FLAG_QPEL (1 << 4)
#if FF_API_DROPCHANGED
/**
* Don't output frames whose parameters differ from first
* decoded frame in stream.
*
* @deprecated callers should implement this functionality in their own code
*/
#  define AV_CODEC_FLAG_DROPCHANGED (1 << 5)
#endif
/**
* Request the encoder to output reconstructed frames, i.e.\ frames that would
* be produced by decoding the encoded bistream. These frames may be retrieved
* by calling avcodec_receive_frame() immediately after a successful call to
* avcodec_receive_packet().
*
* Should only be used with encoders flagged with the
* @ref AV_CODEC_CAP_ENCODER_RECON_FRAME capability.
*
* @note
* Each reconstructed frame returned by the encoder corresponds to the last
* encoded packet, i.e. the frames are returned in coded order rather than
* presentation order.
*
* @note
* Frame parameters (like pixel format or dimensions) do not have to match the
* AVCodecContext values. Make sure to use the values from the returned frame.
*/
#define AV_CODEC_FLAG_RECON_FRAME (1 << 6)
/**
* @par decoding
* Request the decoder to propagate each packet's AVPacket.opaque and
* AVPacket.opaque_ref to its corresponding output AVFrame.
*
* @par encoding:
* Request the encoder to propagate each frame's AVFrame.opaque and
* AVFrame.opaque_ref values to its corresponding output AVPacket.
*
* @par
* May only be set on encoders that have the
* @ref AV_CODEC_CAP_ENCODER_REORDERED_OPAQUE capability flag.
*
* @note
* While in typical cases one input frame produces exactly one output packet
* (perhaps after a delay), in general the mapping of frames to packets is
* M-to-N, so
* - Any number of input frames may be associated with any given output packet.
*   This includes zero - e.g. some encoders may output packets that carry only
*   metadata about the whole stream.
* - A given input frame may be associated with any number of output packets.
*   Again this includes zero - e.g. some encoders may drop frames under certain
*   conditions.
* .
* This implies that when using this flag, the caller must NOT assume that
* - a given input frame's opaques will necessarily appear on some output
* packet;
* - every output packet will have some non-NULL opaque value.
* .
* When an output packet contains multiple frames, the opaque values will be
* taken from the first of those.
*
* @note
* The converse holds for decoders, with frames and packets switched.
*/
#define AV_CODEC_FLAG_COPY_OPAQUE (1 << 7)
/**
* Signal to the encoder that the values of AVFrame.duration are valid and
* should be used (typically for transferring them to output packets).
*
* If this flag is not set, frame durations are ignored.
*/
#define AV_CODEC_FLAG_FRAME_DURATION (1 << 8)
/**
* Use internal 2pass ratecontrol in first pass mode.
*/
#define AV_CODEC_FLAG_PASS1 (1 << 9)
/**
* Use internal 2pass ratecontrol in second pass mode.
*/
#define AV_CODEC_FLAG_PASS2 (1 << 10)
/**
* loop filter.
*/
#define AV_CODEC_FLAG_LOOP_FILTER (1 << 11)
/**
* Only decode/encode grayscale.
*/
#define AV_CODEC_FLAG_GRAY (1 << 13)
/**
* error[?] variables will be set during encoding.
*/
#define AV_CODEC_FLAG_PSNR (1 << 15)
/**
* Use interlaced DCT.
*/
#define AV_CODEC_FLAG_INTERLACED_DCT (1 << 18)
/**
* Force low delay.
*/
#define AV_CODEC_FLAG_LOW_DELAY (1 << 19)
/**
* Place global headers in extradata instead of every keyframe.
*/
#define AV_CODEC_FLAG_GLOBAL_HEADER (1 << 22)
/**
* Use only bitexact stuff (except (I)DCT).
*/
#define AV_CODEC_FLAG_BITEXACT (1 << 23)
/* Fx : Flag for H.263+ extra options */
/**
* H.263 advanced intra coding / MPEG-4 AC prediction
*/
#define AV_CODEC_FLAG_AC_PRED (1 << 24)
/**
* interlaced motion estimation
*/
#define AV_CODEC_FLAG_INTERLACED_ME (1 << 29)
#define AV_CODEC_FLAG_CLOSED_GOP (1U << 31)

/**
* Allow non spec compliant speedup tricks.
*/
#define AV_CODEC_FLAG2_FAST (1 << 0)
/**
* Skip bitstream encoding.
*/
#define AV_CODEC_FLAG2_NO_OUTPUT (1 << 2)
/**
* Place global headers at every keyframe instead of in extradata.
*/
#define AV_CODEC_FLAG2_LOCAL_HEADER (1 << 3)

/**
* Input bitstream might be truncated at a packet boundaries
* instead of only at frame boundaries.
*/
#define AV_CODEC_FLAG2_CHUNKS (1 << 15)
/**
* Discard cropping information from SPS.
*/
#define AV_CODEC_FLAG2_IGNORE_CROP (1 << 16)

/**
* Show all frames before the first keyframe
*/
#define AV_CODEC_FLAG2_SHOW_ALL (1 << 22)
/**
* Export motion vectors through frame side data
*/
#define AV_CODEC_FLAG2_EXPORT_MVS (1 << 28)
/**
* Do not skip samples and export skip information as frame side data
*/
#define AV_CODEC_FLAG2_SKIP_MANUAL (1 << 29)
/**
* Do not reset ASS ReadOrder field on flush (subtitles decoding)
*/
#define AV_CODEC_FLAG2_RO_FLUSH_NOOP (1 << 30)
/**
* Generate/parse ICC profiles on encode/decode, as appropriate for the type of
* file. No effect on codecs which cannot contain embedded ICC profiles, or
* when compiled without support for lcms2.
*/
#define AV_CODEC_FLAG2_ICC_PROFILES (1U << 31)

/* Exported side data.
  These flags can be passed in AVCodecContext.export_side_data before
  initialization.
*/
/**
* Export motion vectors through frame side data
*/
#define AV_CODEC_EXPORT_DATA_MVS (1 << 0)
/**
* Export encoder Producer Reference Time through packet side data
*/
#define AV_CODEC_EXPORT_DATA_PRFT (1 << 1)
/**
* Decoding only.
* Export the AVVideoEncParams structure through frame side data.
*/
#define AV_CODEC_EXPORT_DATA_VIDEO_ENC_PARAMS (1 << 2)
/**
* Decoding only.
* Do not apply film grain, export it instead.
*/
#define AV_CODEC_EXPORT_DATA_FILM_GRAIN (1 << 3)

/**
* The decoder will keep a reference to the frame and may reuse it later.
*/
#define AV_GET_BUFFER_FLAG_REF (1 << 0)

/**
* The encoder will keep a reference to the packet and may reuse it later.
*/
#define AV_GET_ENCODE_BUFFER_FLAG_REF (1 << 0)

/**
* main external API structure.
* New fields can be added to the end with minor version bumps.
* Removal, reordering and changes to existing fields require a major
* version bump.
* You can use AVOptions (av_opt* / av_set/get*()) to access these fields from
* user applications. The name string for AVOptions options matches the
* associated command line parameter name and can be found in
* libavcodec/options_table.h The AVOption/command line parameter names differ
* in some cases from the C structure field names for historic reasons or
* brevity. sizeof(AVCodecContext) must not be used outside libav*.
*/
typedef struct AVCodecContext {
 /**
  * information on struct for av_log
  * - set by avcodec_alloc_context3
  */
 const AVClass* av_class;
 int log_level_offset;

 enum AVMediaType codec_type; /* see AVMEDIA_TYPE_xxx */
 const struct AVCodec* codec;
 enum AVCodecID codec_id; /* see AV_CODEC_ID_xxx */

 /**
  * fourcc (LSB first, so "ABCD" -> ('D'<<24) + ('C'<<16) + ('B'<<8) + 'A').
  * This is used to work around some encoder bugs.
  * A demuxer should set this to what is stored in the field used to identify
  * the codec. If there are multiple such fields in a container then the
  * demuxer should choose the one which maximizes the information about the
  * used codec. If the codec tag field in a container is larger than 32 bits
  * then the demuxer should remap the longer ID to 32 bits with a table or
  * other structure. Alternatively a new extra_codec_tag + size could be added
  * but for this a clear advantage must be demonstrated first.
  * - encoding: Set by user, if not then the default based on codec_id will be
  * used.
  * - decoding: Set by user, will be converted to uppercase by libavcodec
  * during init.
  */
 unsigned int codec_tag;

 void* priv_data;

 /**
  * Private context used for internal data.
  *
  * Unlike priv_data, this is not codec-specific. It is used in general
  * libavcodec functions.
  */
 struct AVCodecInternal* internal;

 /**
  * Private data of the user, can be used to carry app specific stuff.
  * - encoding: Set by user.
  * - decoding: Set by user.
  */
 void* opaque;

 /**
  * the average bitrate
  * - encoding: Set by user; unused for constant quantizer encoding.
  * - decoding: Set by user, may be overwritten by libavcodec
  *             if this info is available in the stream
  */
 int64_t bit_rate;

 /**
  * AV_CODEC_FLAG_*.
  * - encoding: Set by user.
  * - decoding: Set by user.
  */
 int flags;

 /**
  * AV_CODEC_FLAG2_*
  * - encoding: Set by user.
  * - decoding: Set by user.
  */
 int flags2;

 /**
  * some codecs need / can use extradata like Huffman tables.
  * MJPEG: Huffman tables
  * rv10: additional flags
  * MPEG-4: global headers (they can be in the bitstream or here)
  * The allocated memory should be AV_INPUT_BUFFER_PADDING_SIZE bytes larger
  * than extradata_size to avoid problems if it is read with the bitstream
  * reader. The bytewise contents of extradata must not depend on the
  * architecture or CPU endianness. Must be allocated with the av_malloc()
  * family of functions.
  * - encoding: Set/allocated/freed by libavcodec.
  * - decoding: Set/allocated/freed by user.
  */
 uint8_t* extradata;
 int extradata_size;

 /**
  * This is the fundamental unit of time (in seconds) in terms
  * of which frame timestamps are represented. For fixed-fps content,
  * timebase should be 1/framerate and timestamp increments should be
  * identically 1.
  * This often, but not always is the inverse of the frame rate or field rate
  * for video. 1/time_base is not the average frame rate if the frame rate is
  * not constant.
  *
  * Like containers, elementary streams also can store timestamps, 1/time_base
  * is the unit in which these timestamps are specified.
  * As example of such codec time base see ISO/IEC 14496-2:2001(E)
  * vop_time_increment_resolution and fixed_vop_rate
  * (fixed_vop_rate == 0 implies that it is different from the framerate)
  *
  * - encoding: MUST be set by user.
  * - decoding: unused.
  */
 AVRational time_base;

 /**
  * Timebase in which pkt_dts/pts and AVPacket.dts/pts are expressed.
  * - encoding: unused.
  * - decoding: set by user.
  */
 AVRational pkt_timebase;

 /**
  * - decoding: For codecs that store a framerate value in the compressed
  *             bitstream, the decoder may export it here. { 0, 1} when
  *             unknown.
  * - encoding: May be used to signal the framerate of CFR content to an
  *             encoder.
  */
 AVRational framerate;

#if FF_API_TICKS_PER_FRAME
 /**
  * For some codecs, the time base is closer to the field rate than the frame
  * rate. Most notably, H.264 and MPEG-2 specify time_base as half of frame
  * duration if no telecine is used ...
  *
  * Set to time_base ticks per frame. Default 1, e.g., H.264/MPEG-2 set it
  * to 2.
  *
  * @deprecated
  * - decoding: Use AVCodecDescriptor.props & AV_CODEC_PROP_FIELDS
  * - encoding: Set AVCodecContext.framerate instead
  *
  */
 attribute_deprecated int ticks_per_frame;
#endif

 /**
  * Codec delay.
  *
  * Encoding: Number of frames delay there will be from the encoder input to
  *           the decoder output. (we assume the decoder matches the spec)
  * Decoding: Number of frames delay in addition to what a standard decoder
  *           as specified in the spec would produce.
  *
  * Video:
  *   Number of frames the decoded output will be delayed relative to the
  *   encoded input.
  *
  * Audio:
  *   For encoding, this field is unused (see initial_padding).
  *
  *   For decoding, this is the number of samples the decoder needs to
  *   output before the decoder's output is valid. When seeking, you should
  *   start decoding this many samples prior to your desired seek point.
  *
  * - encoding: Set by libavcodec.
  * - decoding: Set by libavcodec.
  */
 int delay;

 /* video only */
 /**
  * picture width / height.
  *
  * @note Those fields may not match the values of the last
  * AVFrame output by avcodec_receive_frame() due frame
  * reordering.
  *
  * - encoding: MUST be set by user.
  * - decoding: May be set by the user before opening the decoder if known e.g.
  *             from the container. Some decoders will require the dimensions
  *             to be set by the caller. During decoding, the decoder may
  *             overwrite those values as required while parsing the data.
  */
 int width, height;

 /**
  * Bitstream width / height, may be different from width/height e.g. when
  * the decoded frame is cropped before being output or lowres is enabled.
  *
  * @note Those field may not match the value of the last
  * AVFrame output by avcodec_receive_frame() due frame
  * reordering.
  *
  * - encoding: unused
  * - decoding: May be set by the user before opening the decoder if known
  *             e.g. from the container. During decoding, the decoder may
  *             overwrite those values as required while parsing the data.
  */
 int coded_width, coded_height;

 /**
  * sample aspect ratio (0 if unknown)
  * That is the width of a pixel divided by the height of the pixel.
  * Numerator and denominator must be relatively prime and smaller than 256 for
  * some video standards.
  * - encoding: Set by user.
  * - decoding: Set by libavcodec.
  */
 AVRational sample_aspect_ratio;

 /**
  * Pixel format, see AV_PIX_FMT_xxx.
  * May be set by the demuxer if known from headers.
  * May be overridden by the decoder if it knows better.
  *
  * @note This field may not match the value of the last
  * AVFrame output by avcodec_receive_frame() due frame
  * reordering.
  *
  * - encoding: Set by user.
  * - decoding: Set by user if known, overridden by libavcodec while
  *             parsing the data.
  */
 enum AVPixelFormat pix_fmt;

 /**
  * Nominal unaccelerated pixel format, see AV_PIX_FMT_xxx.
  * - encoding: unused.
  * - decoding: Set by libavcodec before calling get_format()
  */
 enum AVPixelFormat sw_pix_fmt;

 /**
  * Chromaticity coordinates of the source primaries.
  * - encoding: Set by user
  * - decoding: Set by libavcodec
  */
 enum AVColorPrimaries color_primaries;

 /**
  * Color Transfer Characteristic.
  * - encoding: Set by user
  * - decoding: Set by libavcodec
  */
 enum AVColorTransferCharacteristic color_trc;

 /**
  * YUV colorspace type.
  * - encoding: Set by user
  * - decoding: Set by libavcodec
  */
 enum AVColorSpace colorspace;

 /**
  * MPEG vs JPEG YUV range.
  * - encoding: Set by user to override the default output color range value,
  *   If not specified, libavcodec sets the color range depending on the
  *   output format.
  * - decoding: Set by libavcodec, can be set by the user to propagate the
  *   color range to components reading from the decoder context.
  */
 enum AVColorRange color_range;

 /**
  * This defines the location of chroma samples.
  * - encoding: Set by user
  * - decoding: Set by libavcodec
  */
 enum AVChromaLocation chroma_sample_location;

 /** Field order
  * - encoding: set by libavcodec
  * - decoding: Set by user.
  */
 enum AVFieldOrder field_order;

 /**
  * number of reference frames
  * - encoding: Set by user.
  * - decoding: Set by lavc.
  */
 int refs;

 /**
  * Size of the frame reordering buffer in the decoder.
  * For MPEG-2 it is 1 IPB or 0 low delay IP.
  * - encoding: Set by libavcodec.
  * - decoding: Set by libavcodec.
  */
 int has_b_frames;

 /**
  * slice flags
  * - encoding: unused
  * - decoding: Set by user.
  */
 int slice_flags;
#define SLICE_FLAG_CODED_ORDER \
 0x0001  ///< draw_horiz_band() is called in coded order instead of display
#define SLICE_FLAG_ALLOW_FIELD \
 0x0002  ///< allow draw_horiz_band() with field slices (MPEG-2 field pics)
#define SLICE_FLAG_ALLOW_PLANE \
 0x0004  ///< allow draw_horiz_band() with 1 component at a time (SVQ1)

 /**
  * If non NULL, 'draw_horiz_band' is called by the libavcodec
  * decoder to draw a horizontal band. It improves cache usage. Not
  * all codecs can do that. You must check the codec capabilities
  * beforehand.
  * When multithreading is used, it may be called from multiple threads
  * at the same time; threads might draw different parts of the same AVFrame,
  * or multiple AVFrames, and there is no guarantee that slices will be drawn
  * in order.
  * The function is also used by hardware acceleration APIs.
  * It is called at least once during frame decoding to pass
  * the data needed for hardware render.
  * In that mode instead of pixel data, AVFrame points to
  * a structure specific to the acceleration API. The application
  * reads the structure and can change some fields to indicate progress
  * or mark state.
  * - encoding: unused
  * - decoding: Set by user.
  * @param height the height of the slice
  * @param y the y position of the slice
  * @param type 1->top field, 2->bottom field, 3->frame
  * @param offset offset into the AVFrame.data from which the slice should be
  * read
  */
 void (*draw_horiz_band)(struct AVCodecContext* s, const AVFrame* src,
                         int offset[AV_NUM_DATA_POINTERS], int y, int type,
                         int height);

 /**
  * Callback to negotiate the pixel format. Decoding only, may be set by the
  * caller before avcodec_open2().
  *
  * Called by some decoders to select the pixel format that will be used for
  * the output frames. This is mainly used to set up hardware acceleration,
  * then the provided format list contains the corresponding hwaccel pixel
  * formats alongside the "software" one. The software pixel format may also
  * be retrieved from \ref sw_pix_fmt.
  *
  * This callback will be called when the coded frame properties (such as
  * resolution, pixel format, etc.) change and more than one output format is
  * supported for those new properties. If a hardware pixel format is chosen
  * and initialization for it fails, the callback may be called again
  * immediately.
  *
  * This callback may be called from different threads if the decoder is
  * multi-threaded, but not from more than one thread simultaneously.
  *
  * @param fmt list of formats which may be used in the current
  *            configuration, terminated by AV_PIX_FMT_NONE.
  * @warning Behavior is undefined if the callback returns a value other
  *          than one of the formats in fmt or AV_PIX_FMT_NONE.
  * @return the chosen format or AV_PIX_FMT_NONE
  */
 enum AVPixelFormat (*get_format)(struct AVCodecContext* s,
                                  const enum AVPixelFormat* fmt);

 /**
  * maximum number of B-frames between non-B-frames
  * Note: The output will be delayed by max_b_frames+1 relative to the input.
  * - encoding: Set by user.
  * - decoding: unused
  */
 int max_b_frames;

 /**
  * qscale factor between IP and B-frames
  * If > 0 then the last P-frame quantizer will be used (q=
  * lastp_q*factor+offset). If < 0 then normal ratecontrol will be done (q=
  * -normal_q*factor+offset).
  * - encoding: Set by user.
  * - decoding: unused
  */
 float b_quant_factor;

 /**
  * qscale offset between IP and B-frames
  * - encoding: Set by user.
  * - decoding: unused
  */
 float b_quant_offset;

 /**
  * qscale factor between P- and I-frames
  * If > 0 then the last P-frame quantizer will be used (q = lastp_q * factor +
  * offset). If < 0 then normal ratecontrol will be done (q=
  * -normal_q*factor+offset).
  * - encoding: Set by user.
  * - decoding: unused
  */
 float i_quant_factor;

 /**
  * qscale offset between P and I-frames
  * - encoding: Set by user.
  * - decoding: unused
  */
 float i_quant_offset;

 /**
  * luminance masking (0-> disabled)
  * - encoding: Set by user.
  * - decoding: unused
  */
 float lumi_masking;

 /**
  * temporary complexity masking (0-> disabled)
  * - encoding: Set by user.
  * - decoding: unused
  */
 float temporal_cplx_masking;

 /**
  * spatial complexity masking (0-> disabled)
  * - encoding: Set by user.
  * - decoding: unused
  */
 float spatial_cplx_masking;

 /**
  * p block masking (0-> disabled)
  * - encoding: Set by user.
  * - decoding: unused
  */
 float p_masking;

 /**
  * darkness masking (0-> disabled)
  * - encoding: Set by user.
  * - decoding: unused
  */
 float dark_masking;

 /**
  * noise vs. sse weight for the nsse comparison function
  * - encoding: Set by user.
  * - decoding: unused
  */
 int nsse_weight;

 /**
  * motion estimation comparison function
  * - encoding: Set by user.
  * - decoding: unused
  */
 int me_cmp;
 /**
  * subpixel motion estimation comparison function
  * - encoding: Set by user.
  * - decoding: unused
  */
 int me_sub_cmp;
 /**
  * macroblock comparison function (not supported yet)
  * - encoding: Set by user.
  * - decoding: unused
  */
 int mb_cmp;
 /**
  * interlaced DCT comparison function
  * - encoding: Set by user.
  * - decoding: unused
  */
 int ildct_cmp;
#define FF_CMP_SAD 0
#define FF_CMP_SSE 1
#define FF_CMP_SATD 2
#define FF_CMP_DCT 3
#define FF_CMP_PSNR 4
#define FF_CMP_BIT 5
#define FF_CMP_RD 6
#define FF_CMP_ZERO 7
#define FF_CMP_VSAD 8
#define FF_CMP_VSSE 9
#define FF_CMP_NSSE 10
#define FF_CMP_W53 11
#define FF_CMP_W97 12
#define FF_CMP_DCTMAX 13
#define FF_CMP_DCT264 14
#define FF_CMP_MEDIAN_SAD 15
#define FF_CMP_CHROMA 256

 /**
  * ME diamond size & shape
  * - encoding: Set by user.
  * - decoding: unused
  */
 int dia_size;

 /**
  * amount of previous MV predictors (2a+1 x 2a+1 square)
  * - encoding: Set by user.
  * - decoding: unused
  */
 int last_predictor_count;

 /**
  * motion estimation prepass comparison function
  * - encoding: Set by user.
  * - decoding: unused
  */
 int me_pre_cmp;

 /**
  * ME prepass diamond size & shape
  * - encoding: Set by user.
  * - decoding: unused
  */
 int pre_dia_size;

 /**
  * subpel ME quality
  * - encoding: Set by user.
  * - decoding: unused
  */
 int me_subpel_quality;

 /**
  * maximum motion estimation search range in subpel units
  * If 0 then no limit.
  *
  * - encoding: Set by user.
  * - decoding: unused
  */
 int me_range;

 /**
  * macroblock decision mode
  * - encoding: Set by user.
  * - decoding: unused
  */
 int mb_decision;
#define FF_MB_DECISION_SIMPLE 0  ///< uses mb_cmp
#define FF_MB_DECISION_BITS 1  ///< chooses the one which needs the fewest bits
#define FF_MB_DECISION_RD 2    ///< rate distortion

 /**
  * custom intra quantization matrix
  * Must be allocated with the av_malloc() family of functions, and will be
  * freed in avcodec_free_context().
  * - encoding: Set/allocated by user, freed by libavcodec. Can be NULL.
  * - decoding: Set/allocated/freed by libavcodec.
  */
 uint16_t* intra_matrix;

 /**
  * custom inter quantization matrix
  * Must be allocated with the av_malloc() family of functions, and will be
  * freed in avcodec_free_context().
  * - encoding: Set/allocated by user, freed by libavcodec. Can be NULL.
  * - decoding: Set/allocated/freed by libavcodec.
  */
 uint16_t* inter_matrix;

 /**
  * custom intra quantization matrix
  * - encoding: Set by user, can be NULL.
  * - decoding: unused.
  */
 uint16_t* chroma_intra_matrix;

 /**
  * precision of the intra DC coefficient - 8
  * - encoding: Set by user.
  * - decoding: Set by libavcodec
  */
 int intra_dc_precision;

 /**
  * minimum MB Lagrange multiplier
  * - encoding: Set by user.
  * - decoding: unused
  */
 int mb_lmin;

 /**
  * maximum MB Lagrange multiplier
  * - encoding: Set by user.
  * - decoding: unused
  */
 int mb_lmax;

 /**
  * - encoding: Set by user.
  * - decoding: unused
  */
 int bidir_refine;

 /**
  * minimum GOP size
  * - encoding: Set by user.
  * - decoding: unused
  */
 int keyint_min;

 /**
  * the number of pictures in a group of pictures, or 0 for intra_only
  * - encoding: Set by user.
  * - decoding: unused
  */
 int gop_size;

 /**
  * Note: Value depends upon the compare function used for fullpel ME.
  * - encoding: Set by user.
  * - decoding: unused
  */
 int mv0_threshold;

 /**
  * Number of slices.
  * Indicates number of picture subdivisions. Used for parallelized
  * decoding.
  * - encoding: Set by user
  * - decoding: unused
  */
 int slices;

 /* audio only */
 int sample_rate;  ///< samples per second

 /**
  * audio sample format
  * - encoding: Set by user.
  * - decoding: Set by libavcodec.
  */
 enum AVSampleFormat sample_fmt;  ///< sample format

 /**
  * Audio channel layout.
  * - encoding: must be set by the caller, to one of AVCodec.ch_layouts.
  * - decoding: may be set by the caller if known e.g. from the container.
  *             The decoder can then override during decoding as needed.
  */
 AVChannelLayout ch_layout;

 /* The following data should not be initialized. */
 /**
  * Number of samples per channel in an audio frame.
  *
  * - encoding: set by libavcodec in avcodec_open2(). Each submitted frame
  *   except the last must contain exactly frame_size samples per channel.
  *   May be 0 when the codec has AV_CODEC_CAP_VARIABLE_FRAME_SIZE set, then
  * the frame size is not restricted.
  * - decoding: may be set by some decoders to indicate constant frame size
  */
 int frame_size;

 /**
  * number of bytes per packet if constant and known or 0
  * Used by some WAV based audio codecs.
  */
 int block_align;

 /**
  * Audio cutoff bandwidth (0 means "automatic")
  * - encoding: Set by user.
  * - decoding: unused
  */
 int cutoff;

 /**
  * Type of service that the audio stream conveys.
  * - encoding: Set by user.
  * - decoding: Set by libavcodec.
  */
 enum AVAudioServiceType audio_service_type;

 /**
  * desired sample format
  * - encoding: Not used.
  * - decoding: Set by user.
  * Decoder will decode to this format if it can.
  */
 enum AVSampleFormat request_sample_fmt;

 /**
  * Audio only. The number of "priming" samples (padding) inserted by the
  * encoder at the beginning of the audio. I.e. this number of leading
  * decoded samples must be discarded by the caller to get the original audio
  * without leading padding.
  *
  * - decoding: unused
  * - encoding: Set by libavcodec. The timestamps on the output packets are
  *             adjusted by the encoder so that they always refer to the
  *             first sample of the data actually contained in the packet,
  *             including any added padding.  E.g. if the timebase is
  *             1/samplerate and the timestamp of the first input sample is
  *             0, the timestamp of the first output packet will be
  *             -initial_padding.
  */
 int initial_padding;

 /**
  * Audio only. The amount of padding (in samples) appended by the encoder to
  * the end of the audio. I.e. this number of decoded samples must be
  * discarded by the caller from the end of the stream to get the original
  * audio without any trailing padding.
  *
  * - decoding: unused
  * - encoding: unused
  */
 int trailing_padding;

 /**
  * Number of samples to skip after a discontinuity
  * - decoding: unused
  * - encoding: set by libavcodec
  */
 int seek_preroll;

 /**
  * This callback is called at the beginning of each frame to get data
  * buffer(s) for it. There may be one contiguous buffer for all the data or
  * there may be a buffer per each data plane or anything in between. What
  * this means is, you may set however many entries in buf[] you feel
  * necessary. Each buffer must be reference-counted using the AVBuffer API
  * (see description of buf[] below).
  *
  * The following fields will be set in the frame before this callback is
  * called:
  * - format
  * - width, height (video only)
  * - sample_rate, channel_layout, nb_samples (audio only)
  * Their values may differ from the corresponding values in
  * AVCodecContext. This callback must use the frame values, not the codec
  * context values, to calculate the required buffer size.
  *
  * This callback must fill the following fields in the frame:
  * - data[]
  * - linesize[]
  * - extended_data:
  *   * if the data is planar audio with more than 8 channels, then this
  *     callback must allocate and fill extended_data to contain all pointers
  *     to all data planes. data[] must hold as many pointers as it can.
  *     extended_data must be allocated with av_malloc() and will be freed in
  *     av_frame_unref().
  *   * otherwise extended_data must point to data
  * - buf[] must contain one or more pointers to AVBufferRef structures. Each
  * of the frame's data and extended_data pointers must be contained in these.
  * That is, one AVBufferRef for each allocated chunk of memory, not
  * necessarily one AVBufferRef per data[] entry. See: av_buffer_create(),
  * av_buffer_alloc(), and av_buffer_ref().
  * - extended_buf and nb_extended_buf must be allocated with av_malloc() by
  *   this callback and filled with the extra buffers if there are more
  *   buffers than buf[] can hold. extended_buf will be freed in
  *   av_frame_unref().
  *
  * If AV_CODEC_CAP_DR1 is not set then get_buffer2() must call
  * avcodec_default_get_buffer2() instead of providing buffers allocated by
  * some other means.
  *
  * Each data plane must be aligned to the maximum required by the target
  * CPU.
  *
  * @see avcodec_default_get_buffer2()
  *
  * Video:
  *
  * If AV_GET_BUFFER_FLAG_REF is set in flags then the frame may be reused
  * (read and/or written to if it is writable) later by libavcodec.
  *
  * avcodec_align_dimensions2() should be used to find the required width and
  * height, as they normally need to be rounded up to the next multiple of 16.
  *
  * Some decoders do not support linesizes changing between frames.
  *
  * If frame multithreading is used, this callback may be called from a
  * different thread, but not from more than one at once. Does not need to be
  * reentrant.
  *
  * @see avcodec_align_dimensions2()
  *
  * Audio:
  *
  * Decoders request a buffer of a particular size by setting
  * AVFrame.nb_samples prior to calling get_buffer2(). The decoder may,
  * however, utilize only part of the buffer by setting AVFrame.nb_samples
  * to a smaller value in the output frame.
  *
  * As a convenience, av_samples_get_buffer_size() and
  * av_samples_fill_arrays() in libavutil may be used by custom get_buffer2()
  * functions to find the required data size and to fill data pointers and
  * linesize. In AVFrame.linesize, only linesize[0] may be set for audio
  * since all planes must be the same size.
  *
  * @see av_samples_get_buffer_size(), av_samples_fill_arrays()
  *
  * - encoding: unused
  * - decoding: Set by libavcodec, user can override.
  */
 int (*get_buffer2)(struct AVCodecContext* s, AVFrame* frame, int flags);

 /* - encoding parameters */
 /**
  * number of bits the bitstream is allowed to diverge from the reference.
  *           the reference can be CBR (for CBR pass1) or VBR (for pass2)
  * - encoding: Set by user; unused for constant quantizer encoding.
  * - decoding: unused
  */
 int bit_rate_tolerance;

 /**
  * Global quality for codecs which cannot change it per frame.
  * This should be proportional to MPEG-1/2/4 qscale.
  * - encoding: Set by user.
  * - decoding: unused
  */
 int global_quality;

 /**
  * - encoding: Set by user.
  * - decoding: unused
  */
 int compression_level;
#define FF_COMPRESSION_DEFAULT -1

 float qcompress;  ///< amount of qscale change between easy & hard scenes
                   ///< (0.0-1.0)
 float qblur;      ///< amount of qscale smoothing over time (0.0-1.0)

 /**
  * minimum quantizer
  * - encoding: Set by user.
  * - decoding: unused
  */
 int qmin;

 /**
  * maximum quantizer
  * - encoding: Set by user.
  * - decoding: unused
  */
 int qmax;

 /**
  * maximum quantizer difference between frames
  * - encoding: Set by user.
  * - decoding: unused
  */
 int max_qdiff;

 /**
  * decoder bitstream buffer size
  * - encoding: Set by user.
  * - decoding: May be set by libavcodec.
  */
 int rc_buffer_size;

 /**
  * ratecontrol override, see RcOverride
  * - encoding: Allocated/set/freed by user.
  * - decoding: unused
  */
 int rc_override_count;
 RcOverride* rc_override;

 /**
  * maximum bitrate
  * - encoding: Set by user.
  * - decoding: Set by user, may be overwritten by libavcodec.
  */
 int64_t rc_max_rate;

 /**
  * minimum bitrate
  * - encoding: Set by user.
  * - decoding: unused
  */
 int64_t rc_min_rate;

 /**
  * Ratecontrol attempt to use, at maximum, <value> of what can be used without
  * an underflow.
  * - encoding: Set by user.
  * - decoding: unused.
  */
 float rc_max_available_vbv_use;

 /**
  * Ratecontrol attempt to use, at least, <value> times the amount needed to
  * prevent a vbv overflow.
  * - encoding: Set by user.
  * - decoding: unused.
  */
 float rc_min_vbv_overflow_use;

 /**
  * Number of bits which should be loaded into the rc buffer before decoding
  * starts.
  * - encoding: Set by user.
  * - decoding: unused
  */
 int rc_initial_buffer_occupancy;

 /**
  * trellis RD quantization
  * - encoding: Set by user.
  * - decoding: unused
  */
 int trellis;

 /**
  * pass1 encoding statistics output buffer
  * - encoding: Set by libavcodec.
  * - decoding: unused
  */
 char* stats_out;

 /**
  * pass2 encoding statistics input buffer
  * Concatenated stuff from stats_out of pass1 should be placed here.
  * - encoding: Allocated/set/freed by user.
  * - decoding: unused
  */
 char* stats_in;

 /**
  * Work around bugs in encoders which sometimes cannot be detected
  * automatically.
  * - encoding: Set by user
  * - decoding: Set by user
  */
 int workaround_bugs;
#define FF_BUG_AUTODETECT 1  ///< autodetection
#define FF_BUG_XVID_ILACE 4
#define FF_BUG_UMP4 8
#define FF_BUG_NO_PADDING 16
#define FF_BUG_AMV 32
#define FF_BUG_QPEL_CHROMA 64
#define FF_BUG_STD_QPEL 128
#define FF_BUG_QPEL_CHROMA2 256
#define FF_BUG_DIRECT_BLOCKSIZE 512
#define FF_BUG_EDGE 1024
#define FF_BUG_HPEL_CHROMA 2048
#define FF_BUG_DC_CLIP 4096
#define FF_BUG_MS \
 8192  ///< Work around various bugs in Microsoft's broken decoders.
#define FF_BUG_TRUNCATED 16384
#define FF_BUG_IEDGE 32768

 /**
  * strictly follow the standard (MPEG-4, ...).
  * - encoding: Set by user.
  * - decoding: Set by user.
  * Setting this to STRICT or higher means the encoder and decoder will
  * generally do stupid things, whereas setting it to unofficial or lower
  * will mean the encoder might produce output that is not supported by all
  * spec-compliant decoders. Decoders don't differentiate between normal,
  * unofficial and experimental (that is, they always try to decode things
  * when they can) unless they are explicitly asked to behave stupidly
  * (=strictly conform to the specs)
  * This may only be set to one of the FF_COMPLIANCE_* values in defs.h.
  */
 int strict_std_compliance;

 /**
  * error concealment flags
  * - encoding: unused
  * - decoding: Set by user.
  */
 int error_concealment;
#define FF_EC_GUESS_MVS 1
#define FF_EC_DEBLOCK 2
#define FF_EC_FAVOR_INTER 256

 /**
  * debug
  * - encoding: Set by user.
  * - decoding: Set by user.
  */
 int debug;
#define FF_DEBUG_PICT_INFO 1
#define FF_DEBUG_RC 2
#define FF_DEBUG_BITSTREAM 4
#define FF_DEBUG_MB_TYPE 8
#define FF_DEBUG_QP 16
#define FF_DEBUG_DCT_COEFF 0x00000040
#define FF_DEBUG_SKIP 0x00000080
#define FF_DEBUG_STARTCODE 0x00000100
#define FF_DEBUG_ER 0x00000400
#define FF_DEBUG_MMCO 0x00000800
#define FF_DEBUG_BUGS 0x00001000
#define FF_DEBUG_BUFFERS 0x00008000
#define FF_DEBUG_THREADS 0x00010000
#define FF_DEBUG_GREEN_MD 0x00800000
#define FF_DEBUG_NOMC 0x01000000

 /**
  * Error recognition; may misdetect some more or less valid parts as errors.
  * This is a bitfield of the AV_EF_* values defined in defs.h.
  *
  * - encoding: Set by user.
  * - decoding: Set by user.
  */
 int err_recognition;

 /**
  * Hardware accelerator in use
  * - encoding: unused.
  * - decoding: Set by libavcodec
  */
 const struct AVHWAccel* hwaccel;

 /**
  * Legacy hardware accelerator context.
  *
  * For some hardware acceleration methods, the caller may use this field to
  * signal hwaccel-specific data to the codec. The struct pointed to by this
  * pointer is hwaccel-dependent and defined in the respective header. Please
  * refer to the FFmpeg HW accelerator documentation to know how to fill
  * this.
  *
  * In most cases this field is optional - the necessary information may also
  * be provided to libavcodec through @ref hw_frames_ctx or @ref
  * hw_device_ctx (see avcodec_get_hw_config()). However, in some cases it
  * may be the only method of signalling some (optional) information.
  *
  * The struct and its contents are owned by the caller.
  *
  * - encoding: May be set by the caller before avcodec_open2(). Must remain
  *             valid until avcodec_free_context().
  * - decoding: May be set by the caller in the get_format() callback.
  *             Must remain valid until the next get_format() call,
  *             or avcodec_free_context() (whichever comes first).
  */
 void* hwaccel_context;

 /**
  * A reference to the AVHWFramesContext describing the input (for encoding)
  * or output (decoding) frames. The reference is set by the caller and
  * afterwards owned (and freed) by libavcodec - it should never be read by
  * the caller after being set.
  *
  * - decoding: This field should be set by the caller from the get_format()
  *             callback. The previous reference (if any) will always be
  *             unreffed by libavcodec before the get_format() call.
  *
  *             If the default get_buffer2() is used with a hwaccel pixel
  *             format, then this AVHWFramesContext will be used for
  *             allocating the frame buffers.
  *
  * - encoding: For hardware encoders configured to use a hwaccel pixel
  *             format, this field should be set by the caller to a reference
  *             to the AVHWFramesContext describing input frames.
  *             AVHWFramesContext.format must be equal to
  *             AVCodecContext.pix_fmt.
  *
  *             This field should be set before avcodec_open2() is called.
  */
 AVBufferRef* hw_frames_ctx;

 /**
  * A reference to the AVHWDeviceContext describing the device which will
  * be used by a hardware encoder/decoder.  The reference is set by the
  * caller and afterwards owned (and freed) by libavcodec.
  *
  * This should be used if either the codec device does not require
  * hardware frames or any that are used are to be allocated internally by
  * libavcodec.  If the user wishes to supply any of the frames used as
  * encoder input or decoder output then hw_frames_ctx should be used
  * instead.  When hw_frames_ctx is set in get_format() for a decoder, this
  * field will be ignored while decoding the associated stream segment, but
  * may again be used on a following one after another get_format() call.
  *
  * For both encoders and decoders this field should be set before
  * avcodec_open2() is called and must not be written to thereafter.
  *
  * Note that some decoders may require this field to be set initially in
  * order to support hw_frames_ctx at all - in that case, all frames
  * contexts used must be created on the same device.
  */
 AVBufferRef* hw_device_ctx;

 /**
  * Bit set of AV_HWACCEL_FLAG_* flags, which affect hardware accelerated
  * decoding (if active).
  * - encoding: unused
  * - decoding: Set by user (either before avcodec_open2(), or in the
  *             AVCodecContext.get_format callback)
  */
 int hwaccel_flags;

 /**
  * Video decoding only.  Sets the number of extra hardware frames which
  * the decoder will allocate for use by the caller.  This must be set
  * before avcodec_open2() is called.
  *
  * Some hardware decoders require all frames that they will use for
  * output to be defined in advance before decoding starts.  For such
  * decoders, the hardware frame pool must therefore be of a fixed size.
  * The extra frames set here are on top of any number that the decoder
  * needs internally in order to operate normally (for example, frames
  * used as reference pictures).
  */
 int extra_hw_frames;

 /**
  * error
  * - encoding: Set by libavcodec if flags & AV_CODEC_FLAG_PSNR.
  * - decoding: unused
  */
 uint64_t error[AV_NUM_DATA_POINTERS];

 /**
  * DCT algorithm, see FF_DCT_* below
  * - encoding: Set by user.
  * - decoding: unused
  */
 int dct_algo;
#define FF_DCT_AUTO 0
#define FF_DCT_FASTINT 1
#define FF_DCT_INT 2
#define FF_DCT_MMX 3
#define FF_DCT_ALTIVEC 5
#define FF_DCT_FAAN 6

 /**
  * IDCT algorithm, see FF_IDCT_* below.
  * - encoding: Set by user.
  * - decoding: Set by user.
  */
 int idct_algo;
#define FF_IDCT_AUTO 0
#define FF_IDCT_INT 1
#define FF_IDCT_SIMPLE 2
#define FF_IDCT_SIMPLEMMX 3
#define FF_IDCT_ARM 7
#define FF_IDCT_ALTIVEC 8
#define FF_IDCT_SIMPLEARM 10
#define FF_IDCT_XVID 14
#define FF_IDCT_SIMPLEARMV5TE 16
#define FF_IDCT_SIMPLEARMV6 17
#define FF_IDCT_FAAN 20
#define FF_IDCT_SIMPLENEON 22
#define FF_IDCT_SIMPLEAUTO 128

 /**
  * bits per sample/pixel from the demuxer (needed for huffyuv).
  * - encoding: Set by libavcodec.
  * - decoding: Set by user.
  */
 int bits_per_coded_sample;

 /**
  * Bits per sample/pixel of internal libavcodec pixel/sample format.
  * - encoding: set by user.
  * - decoding: set by libavcodec.
  */
 int bits_per_raw_sample;

 /**
  * thread count
  * is used to decide how many independent tasks should be passed to execute()
  * - encoding: Set by user.
  * - decoding: Set by user.
  */
 int thread_count;

 /**
  * Which multithreading methods to use.
  * Use of FF_THREAD_FRAME will increase decoding delay by one frame per
  * thread, so clients which cannot provide future frames should not use it.
  *
  * - encoding: Set by user, otherwise the default is used.
  * - decoding: Set by user, otherwise the default is used.
  */
 int thread_type;
#define FF_THREAD_FRAME 1  ///< Decode more than one frame at once
#define FF_THREAD_SLICE \
 2  ///< Decode more than one part of a single frame at once

 /**
  * Which multithreading methods are in use by the codec.
  * - encoding: Set by libavcodec.
  * - decoding: Set by libavcodec.
  */
 int active_thread_type;

 /**
  * The codec may call this to execute several independent things.
  * It will return only after finishing all tasks.
  * The user may replace this with some multithreaded implementation,
  * the default implementation will execute the parts serially.
  * @param count the number of things to execute
  * - encoding: Set by libavcodec, user can override.
  * - decoding: Set by libavcodec, user can override.
  */
 int (*execute)(struct AVCodecContext* c,
                int (*func)(struct AVCodecContext* c2, void* arg), void* arg2,
                int* ret, int count, int size);

 /**
  * The codec may call this to execute several independent things.
  * It will return only after finishing all tasks.
  * The user may replace this with some multithreaded implementation,
  * the default implementation will execute the parts serially.
  * @param c context passed also to func
  * @param count the number of things to execute
  * @param arg2 argument passed unchanged to func
  * @param ret return values of executed functions, must have space for "count"
  * values. May be NULL.
  * @param func function that will be called count times, with jobnr from 0 to
  * count-1. threadnr will be in the range 0 to c->thread_count-1 < MAX_THREADS
  * and so that no two instances of func executing at the same time will have
  * the same threadnr.
  * @return always 0 currently, but code should handle a future improvement
  * where when any call to func returns < 0 no further calls to func may be
  * done and < 0 is returned.
  * - encoding: Set by libavcodec, user can override.
  * - decoding: Set by libavcodec, user can override.
  */
 int (*execute2)(struct AVCodecContext* c,
                 int (*func)(struct AVCodecContext* c2, void* arg, int jobnr,
                             int threadnr),
                 void* arg2, int* ret, int count);

 /**
  * profile
  * - encoding: Set by user.
  * - decoding: Set by libavcodec.
  * See the AV_PROFILE_* defines in defs.h.
  */
 int profile;
#if FF_API_FF_PROFILE_LEVEL
 /** @deprecated The following defines are deprecated; use AV_PROFILE_*
  * in defs.h instead. */
#  define FF_PROFILE_UNKNOWN -99
#  define FF_PROFILE_RESERVED -100

#  define FF_PROFILE_AAC_MAIN 0
#  define FF_PROFILE_AAC_LOW 1
#  define FF_PROFILE_AAC_SSR 2
#  define FF_PROFILE_AAC_LTP 3
#  define FF_PROFILE_AAC_HE 4
#  define FF_PROFILE_AAC_HE_V2 28
#  define FF_PROFILE_AAC_LD 22
#  define FF_PROFILE_AAC_ELD 38
#  define FF_PROFILE_MPEG2_AAC_LOW 128
#  define FF_PROFILE_MPEG2_AAC_HE 131

#  define FF_PROFILE_DNXHD 0
#  define FF_PROFILE_DNXHR_LB 1
#  define FF_PROFILE_DNXHR_SQ 2
#  define FF_PROFILE_DNXHR_HQ 3
#  define FF_PROFILE_DNXHR_HQX 4
#  define FF_PROFILE_DNXHR_444 5

#  define FF_PROFILE_DTS 20
#  define FF_PROFILE_DTS_ES 30
#  define FF_PROFILE_DTS_96_24 40
#  define FF_PROFILE_DTS_HD_HRA 50
#  define FF_PROFILE_DTS_HD_MA 60
#  define FF_PROFILE_DTS_EXPRESS 70
#  define FF_PROFILE_DTS_HD_MA_X 61
#  define FF_PROFILE_DTS_HD_MA_X_IMAX 62

#  define FF_PROFILE_EAC3_DDP_ATMOS 30

#  define FF_PROFILE_TRUEHD_ATMOS 30

#  define FF_PROFILE_MPEG2_422 0
#  define FF_PROFILE_MPEG2_HIGH 1
#  define FF_PROFILE_MPEG2_SS 2
#  define FF_PROFILE_MPEG2_SNR_SCALABLE 3
#  define FF_PROFILE_MPEG2_MAIN 4
#  define FF_PROFILE_MPEG2_SIMPLE 5

#  define FF_PROFILE_H264_CONSTRAINED (1 << 9)  // 8+1; constraint_set1_flag
#  define FF_PROFILE_H264_INTRA (1 << 11)       // 8+3; constraint_set3_flag

#  define FF_PROFILE_H264_BASELINE 66
#  define FF_PROFILE_H264_CONSTRAINED_BASELINE \
   (66 | FF_PROFILE_H264_CONSTRAINED)
#  define FF_PROFILE_H264_MAIN 77
#  define FF_PROFILE_H264_EXTENDED 88
#  define FF_PROFILE_H264_HIGH 100
#  define FF_PROFILE_H264_HIGH_10 110
#  define FF_PROFILE_H264_HIGH_10_INTRA (110 | FF_PROFILE_H264_INTRA)
#  define FF_PROFILE_H264_MULTIVIEW_HIGH 118
#  define FF_PROFILE_H264_HIGH_422 122
#  define FF_PROFILE_H264_HIGH_422_INTRA (122 | FF_PROFILE_H264_INTRA)
#  define FF_PROFILE_H264_STEREO_HIGH 128
#  define FF_PROFILE_H264_HIGH_444 144
#  define FF_PROFILE_H264_HIGH_444_PREDICTIVE 244
#  define FF_PROFILE_H264_HIGH_444_INTRA (244 | FF_PROFILE_H264_INTRA)
#  define FF_PROFILE_H264_CAVLC_444 44

#  define FF_PROFILE_VC1_SIMPLE 0
#  define FF_PROFILE_VC1_MAIN 1
#  define FF_PROFILE_VC1_COMPLEX 2
#  define FF_PROFILE_VC1_ADVANCED 3

#  define FF_PROFILE_MPEG4_SIMPLE 0
#  define FF_PROFILE_MPEG4_SIMPLE_SCALABLE 1
#  define FF_PROFILE_MPEG4_CORE 2
#  define FF_PROFILE_MPEG4_MAIN 3
#  define FF_PROFILE_MPEG4_N_BIT 4
#  define FF_PROFILE_MPEG4_SCALABLE_TEXTURE 5
#  define FF_PROFILE_MPEG4_SIMPLE_FACE_ANIMATION 6
#  define FF_PROFILE_MPEG4_BASIC_ANIMATED_TEXTURE 7
#  define FF_PROFILE_MPEG4_HYBRID 8
#  define FF_PROFILE_MPEG4_ADVANCED_REAL_TIME 9
#  define FF_PROFILE_MPEG4_CORE_SCALABLE 10
#  define FF_PROFILE_MPEG4_ADVANCED_CODING 11
#  define FF_PROFILE_MPEG4_ADVANCED_CORE 12
#  define FF_PROFILE_MPEG4_ADVANCED_SCALABLE_TEXTURE 13
#  define FF_PROFILE_MPEG4_SIMPLE_STUDIO 14
#  define FF_PROFILE_MPEG4_ADVANCED_SIMPLE 15

#  define FF_PROFILE_JPEG2000_CSTREAM_RESTRICTION_0 1
#  define FF_PROFILE_JPEG2000_CSTREAM_RESTRICTION_1 2
#  define FF_PROFILE_JPEG2000_CSTREAM_NO_RESTRICTION 32768
#  define FF_PROFILE_JPEG2000_DCINEMA_2K 3
#  define FF_PROFILE_JPEG2000_DCINEMA_4K 4

#  define FF_PROFILE_VP9_0 0
#  define FF_PROFILE_VP9_1 1
#  define FF_PROFILE_VP9_2 2
#  define FF_PROFILE_VP9_3 3

#  define FF_PROFILE_HEVC_MAIN 1
#  define FF_PROFILE_HEVC_MAIN_10 2
#  define FF_PROFILE_HEVC_MAIN_STILL_PICTURE 3
#  define FF_PROFILE_HEVC_REXT 4
#  define FF_PROFILE_HEVC_SCC 9

#  define FF_PROFILE_VVC_MAIN_10 1
#  define FF_PROFILE_VVC_MAIN_10_444 33

#  define FF_PROFILE_AV1_MAIN 0
#  define FF_PROFILE_AV1_HIGH 1
#  define FF_PROFILE_AV1_PROFESSIONAL 2

#  define FF_PROFILE_MJPEG_HUFFMAN_BASELINE_DCT 0xc0
#  define FF_PROFILE_MJPEG_HUFFMAN_EXTENDED_SEQUENTIAL_DCT 0xc1
#  define FF_PROFILE_MJPEG_HUFFMAN_PROGRESSIVE_DCT 0xc2
#  define FF_PROFILE_MJPEG_HUFFMAN_LOSSLESS 0xc3
#  define FF_PROFILE_MJPEG_JPEG_LS 0xf7

#  define FF_PROFILE_SBC_MSBC 1

#  define FF_PROFILE_PRORES_PROXY 0
#  define FF_PROFILE_PRORES_LT 1
#  define FF_PROFILE_PRORES_STANDARD 2
#  define FF_PROFILE_PRORES_HQ 3
#  define FF_PROFILE_PRORES_4444 4
#  define FF_PROFILE_PRORES_XQ 5

#  define FF_PROFILE_ARIB_PROFILE_A 0
#  define FF_PROFILE_ARIB_PROFILE_C 1

#  define FF_PROFILE_KLVA_SYNC 0
#  define FF_PROFILE_KLVA_ASYNC 1

#  define FF_PROFILE_EVC_BASELINE 0
#  define FF_PROFILE_EVC_MAIN 1
#endif

 /**
  * Encoding level descriptor.
  * - encoding: Set by user, corresponds to a specific level defined by the
  *   codec, usually corresponding to the profile level, if not specified it
  *   is set to FF_LEVEL_UNKNOWN.
  * - decoding: Set by libavcodec.
  * See AV_LEVEL_* in defs.h.
  */
 int level;
#if FF_API_FF_PROFILE_LEVEL
 /** @deprecated The following define is deprecated; use AV_LEVEL_UNKOWN
  * in defs.h instead. */
#  define FF_LEVEL_UNKNOWN -99
#endif

 /**
  * Properties of the stream that gets decoded
  * - encoding: unused
  * - decoding: set by libavcodec
  */
 unsigned properties;
#define FF_CODEC_PROPERTY_LOSSLESS 0x00000001
#define FF_CODEC_PROPERTY_CLOSED_CAPTIONS 0x00000002
#define FF_CODEC_PROPERTY_FILM_GRAIN 0x00000004

 /**
  * Skip loop filtering for selected frames.
  * - encoding: unused
  * - decoding: Set by user.
  */
 enum AVDiscard skip_loop_filter;

 /**
  * Skip IDCT/dequantization for selected frames.
  * - encoding: unused
  * - decoding: Set by user.
  */
 enum AVDiscard skip_idct;

 /**
  * Skip decoding for selected frames.
  * - encoding: unused
  * - decoding: Set by user.
  */
 enum AVDiscard skip_frame;

 /**
  * Skip processing alpha if supported by codec.
  * Note that if the format uses pre-multiplied alpha (common with VP6,
  * and recommended due to better video quality/compression)
  * the image will look as if alpha-blended onto a black background.
  * However for formats that do not use pre-multiplied alpha
  * there might be serious artefacts (though e.g. libswscale currently
  * assumes pre-multiplied alpha anyway).
  *
  * - decoding: set by user
  * - encoding: unused
  */
 int skip_alpha;

 /**
  * Number of macroblock rows at the top which are skipped.
  * - encoding: unused
  * - decoding: Set by user.
  */
 int skip_top;

 /**
  * Number of macroblock rows at the bottom which are skipped.
  * - encoding: unused
  * - decoding: Set by user.
  */
 int skip_bottom;

 /**
  * low resolution decoding, 1-> 1/2 size, 2->1/4 size
  * - encoding: unused
  * - decoding: Set by user.
  */
 int lowres;

 /**
  * AVCodecDescriptor
  * - encoding: unused.
  * - decoding: set by libavcodec.
  */
 const struct AVCodecDescriptor* codec_descriptor;

 /**
  * Character encoding of the input subtitles file.
  * - decoding: set by user
  * - encoding: unused
  */
 char* sub_charenc;

 /**
  * Subtitles character encoding mode. Formats or codecs might be adjusting
  * this setting (if they are doing the conversion themselves for instance).
  * - decoding: set by libavcodec
  * - encoding: unused
  */
 int sub_charenc_mode;
#define FF_SUB_CHARENC_MODE_DO_NOTHING \
 -1  ///< do nothing (demuxer outputs a stream supposed to be already in UTF-8,
     ///< or the codec is bitmap for instance)
#define FF_SUB_CHARENC_MODE_AUTOMATIC \
 0  ///< libavcodec will select the mode itself
#define FF_SUB_CHARENC_MODE_PRE_DECODER \
 1  ///< the AVPacket data needs to be recoded to UTF-8 before being fed to the
    ///< decoder, requires iconv
#define FF_SUB_CHARENC_MODE_IGNORE \
 2  ///< neither convert the subtitles, nor check them for valid UTF-8

 /**
  * Header containing style information for text subtitles.
  * For SUBTITLE_ASS subtitle type, it should contain the whole ASS
  * [Script Info] and [V4+ Styles] section, plus the [Events] line and
  * the Format line following. It shouldn't include any Dialogue line.
  * - encoding: Set/allocated/freed by user (before avcodec_open2())
  * - decoding: Set/allocated/freed by libavcodec (by avcodec_open2())
  */
 int subtitle_header_size;
 uint8_t* subtitle_header;

 /**
  * dump format separator.
  * can be ", " or "\n      " or anything else
  * - encoding: Set by user.
  * - decoding: Set by user.
  */
 uint8_t* dump_separator;

 /**
  * ',' separated list of allowed decoders.
  * If NULL then all are allowed
  * - encoding: unused
  * - decoding: set by user
  */
 char* codec_whitelist;

 /**
  * Additional data associated with the entire coded stream.
  *
  * - decoding: may be set by user before calling avcodec_open2().
  * - encoding: may be set by libavcodec after avcodec_open2().
  */
 AVPacketSideData* coded_side_data;
 int nb_coded_side_data;

 /**
  * Bit set of AV_CODEC_EXPORT_DATA_* flags, which affects the kind of
  * metadata exported in frame, packet, or coded stream side data by
  * decoders and encoders.
  *
  * - decoding: set by user
  * - encoding: set by user
  */
 int export_side_data;

 /**
  * The number of pixels per image to maximally accept.
  *
  * - decoding: set by user
  * - encoding: set by user
  */
 int64_t max_pixels;

 /**
  * Video decoding only. Certain video codecs support cropping, meaning that
  * only a sub-rectangle of the decoded frame is intended for display.  This
  * option controls how cropping is handled by libavcodec.
  *
  * When set to 1 (the default), libavcodec will apply cropping internally.
  * I.e. it will modify the output frame width/height fields and offset the
  * data pointers (only by as much as possible while preserving alignment, or
  * by the full amount if the AV_CODEC_FLAG_UNALIGNED flag is set) so that
  * the frames output by the decoder refer only to the cropped area. The
  * crop_* fields of the output frames will be zero.
  *
  * When set to 0, the width/height fields of the output frames will be set
  * to the coded dimensions and the crop_* fields will describe the cropping
  * rectangle. Applying the cropping is left to the caller.
  *
  * @warning When hardware acceleration with opaque output frames is used,
  * libavcodec is unable to apply cropping from the top/left border.
  *
  * @note when this option is set to zero, the width/height fields of the
  * AVCodecContext and output AVFrames have different meanings. The codec
  * context fields store display dimensions (with the coded dimensions in
  * coded_width/height), while the frame fields store the coded dimensions
  * (with the display dimensions being determined by the crop_* fields).
  */
 int apply_cropping;

 /**
  * The percentage of damaged samples to discard a frame.
  *
  * - decoding: set by user
  * - encoding: unused
  */
 int discard_damaged_percentage;

 /**
  * The number of samples per frame to maximally accept.
  *
  * - decoding: set by user
  * - encoding: set by user
  */
 int64_t max_samples;

 /**
  * This callback is called at the beginning of each packet to get a data
  * buffer for it.
  *
  * The following field will be set in the packet before this callback is
  * called:
  * - size
  * This callback must use the above value to calculate the required buffer
  * size, which must padded by at least AV_INPUT_BUFFER_PADDING_SIZE bytes.
  *
  * In some specific cases, the encoder may not use the entire buffer allocated
  * by this callback. This will be reflected in the size value in the packet
  * once returned by avcodec_receive_packet().
  *
  * This callback must fill the following fields in the packet:
  * - data: alignment requirements for AVPacket apply, if any. Some
  * architectures and encoders may benefit from having aligned data.
  * - buf: must contain a pointer to an AVBufferRef structure. The packet's
  *   data pointer must be contained in it. See: av_buffer_create(),
  * av_buffer_alloc(), and av_buffer_ref().
  *
  * If AV_CODEC_CAP_DR1 is not set then get_encode_buffer() must call
  * avcodec_default_get_encode_buffer() instead of providing a buffer allocated
  * by some other means.
  *
  * The flags field may contain a combination of AV_GET_ENCODE_BUFFER_FLAG_
  * flags. They may be used for example to hint what use the buffer may get
  * after being created. Implementations of this callback may ignore flags they
  * don't understand. If AV_GET_ENCODE_BUFFER_FLAG_REF is set in flags then the
  * packet may be reused (read and/or written to if it is writable) later by
  * libavcodec.
  *
  * This callback must be thread-safe, as when frame threading is used, it may
  * be called from multiple threads simultaneously.
  *
  * @see avcodec_default_get_encode_buffer()
  *
  * - encoding: Set by libavcodec, user can override.
  * - decoding: unused
  */
 int (*get_encode_buffer)(struct AVCodecContext* s, AVPacket* pkt, int flags);

 /**
  * Frame counter, set by libavcodec.
  *
  * - decoding: total number of frames returned from the decoder so far.
  * - encoding: total number of frames passed to the encoder so far.
  *
  *   @note the counter is not incremented if encoding/decoding resulted in
  *   an error.
  */
 int64_t frame_num;

 /**
  * Decoding only. May be set by the caller before avcodec_open2() to an
  * av_malloc()'ed array (or via AVOptions). Owned and freed by the decoder
  * afterwards.
  *
  * Side data attached to decoded frames may come from several sources:
  * 1. coded_side_data, which the decoder will for certain types translate
  *    from packet-type to frame-type and attach to frames;
  * 2. side data attached to an AVPacket sent for decoding (same
  *    considerations as above);
  * 3. extracted from the coded bytestream.
  * The first two cases are supplied by the caller and typically come from a
  * container.
  *
  * This array configures decoder behaviour in cases when side data of the
  * same type is present both in the coded bytestream and in the
  * user-supplied side data (items 1. and 2. above). In all cases, at most
  * one instance of each side data type will be attached to output frames. By
  * default it will be the bytestream side data. Adding an
  * AVPacketSideDataType value to this array will flip the preference for
  * this type, thus making the decoder prefer user-supplied side data over
  * bytestream. In case side data of the same type is present both in
  * coded_data and attacked to a packet, the packet instance always has
  * priority.
  *
  * The array may also contain a single -1, in which case the preference is
  * switched for all side data types.
  */
 int* side_data_prefer_packet;
 /**
  * Number of entries in side_data_prefer_packet.
  */
 unsigned nb_side_data_prefer_packet;

 /**
  * Array containing static side data, such as HDR10 CLL / MDCV structures.
  * Side data entries should be allocated by usage of helpers defined in
  * libavutil/frame.h.
  *
  * - encoding: may be set by user before calling avcodec_open2() for
  *             encoder configuration. Afterwards owned and freed by the
  *             encoder.
  * - decoding: unused
  */
 AVFrameSideData** decoded_side_data;
 int nb_decoded_side_data;
} AVCodecContext;

/**
* @defgroup lavc_hwaccel AVHWAccel
*
* @note  Nothing in this structure should be accessed by the user.  At some
*        point in future it will not be externally visible at all.
*
* @{
*/
typedef struct AVHWAccel {
 /**
  * Name of the hardware accelerated codec.
  * The name is globally unique among encoders and among decoders (but an
  * encoder and a decoder can share the same name).
  */
 const char* name;

 /**
  * Type of codec implemented by the hardware accelerator.
  *
  * See AVMEDIA_TYPE_xxx
  */
 enum AVMediaType type;

 /**
  * Codec implemented by the hardware accelerator.
  *
  * See AV_CODEC_ID_xxx
  */
 enum AVCodecID id;

 /**
  * Supported pixel format.
  *
  * Only hardware accelerated formats are supported here.
  */
 enum AVPixelFormat pix_fmt;

 /**
  * Hardware accelerated codec capabilities.
  * see AV_HWACCEL_CODEC_CAP_*
  */
 int capabilities;
} AVHWAccel;

/**
* HWAccel is experimental and is thus avoided in favor of non experimental
* codecs
*/
#define AV_HWACCEL_CODEC_CAP_EXPERIMENTAL 0x0200

/**
* Hardware acceleration should be used for decoding even if the codec level
* used is unknown or higher than the maximum supported level reported by the
* hardware driver.
*
* It's generally a good idea to pass this flag unless you have a specific
* reason not to, as hardware tends to under-report supported levels.
*/
#define AV_HWACCEL_FLAG_IGNORE_LEVEL (1 << 0)

/**
* Hardware acceleration can output YUV pixel formats with a different chroma
* sampling than 4:2:0 and/or other than 8 bits per component.
*/
#define AV_HWACCEL_FLAG_ALLOW_HIGH_DEPTH (1 << 1)

/**
* Hardware acceleration should still be attempted for decoding when the
* codec profile does not match the reported capabilities of the hardware.
*
* For example, this can be used to try to decode baseline profile H.264
* streams in hardware - it will often succeed, because many streams marked
* as baseline profile actually conform to constrained baseline profile.
*
* @warning If the stream is actually not supported then the behaviour is
*          undefined, and may include returning entirely incorrect output
*          while indicating success.
*/
#define AV_HWACCEL_FLAG_ALLOW_PROFILE_MISMATCH (1 << 2)

/**
* Some hardware decoders (namely nvdec) can either output direct decoder
* surfaces, or make an on-device copy and return said copy.
* There is a hard limit on how many decoder surfaces there can be, and it
* cannot be accurately guessed ahead of time.
* For some processing chains, this can be okay, but others will run into the
* limit and in turn produce very confusing errors that require fine tuning of
* more or less obscure options by the user, or in extreme cases cannot be
* resolved at all without inserting an avfilter that forces a copy.
*
* Thus, the hwaccel will by default make a copy for safety and resilience.
* If a users really wants to minimize the amount of copies, they can set this
* flag and ensure their processing chain does not exhaust the surface pool.
*/
#define AV_HWACCEL_FLAG_UNSAFE_OUTPUT (1 << 3)

/**
* @}
*/

enum AVSubtitleType {
 SUBTITLE_NONE,

 SUBTITLE_BITMAP,  ///< A bitmap, pict will be set

 /**
  * Plain text, the text field must be set by the decoder and is
  * authoritative. ass and pict fields may contain approximations.
  */
 SUBTITLE_TEXT,

 /**
  * Formatted text, the ass field must be set by the decoder and is
  * authoritative. pict and text fields may contain approximations.
  */
 SUBTITLE_ASS,
};

#define AV_SUBTITLE_FLAG_FORCED 0x00000001

typedef struct AVSubtitleRect {
 int x;          ///< top left corner  of pict, undefined when pict is not set
 int y;          ///< top left corner  of pict, undefined when pict is not set
 int w;          ///< width            of pict, undefined when pict is not set
 int h;          ///< height           of pict, undefined when pict is not set
 int nb_colors;  ///< number of colors in pict, undefined when pict is not set

 /**
  * data+linesize for the bitmap of this subtitle.
  * Can be set for text/ass as well once they are rendered.
  */
 uint8_t* data[4];
 int linesize[4];

 int flags;
 enum AVSubtitleType type;

 char* text;  ///< 0 terminated plain UTF-8 text

 /**
  * 0 terminated ASS/SSA compatible event line.
  * The presentation of this is unaffected by the other values in this
  * struct.
  */
 char* ass;
} AVSubtitleRect;

typedef struct AVSubtitle {
 uint16_t format;             /* 0 = graphics */
 uint32_t start_display_time; /* relative to packet pts, in ms */
 uint32_t end_display_time;   /* relative to packet pts, in ms */
 unsigned num_rects;
 AVSubtitleRect** rects;
 int64_t pts;  ///< Same as packet pts, in AV_TIME_BASE
} AVSubtitle;

/**
* Return the LIBAVCODEC_VERSION_INT constant.
*/
unsigned avcodec_version(void);

/**
* Return the libavcodec build-time configuration.
*/
const char* avcodec_configuration(void);

/**
* Return the libavcodec license.
*/
const char* avcodec_license(void);

/**
* Allocate an AVCodecContext and set its fields to default values. The
* resulting struct should be freed with avcodec_free_context().
*
* @param codec if non-NULL, allocate private data and initialize defaults
*              for the given codec. It is illegal to then call avcodec_open2()
*              with a different codec.
*              If NULL, then the codec-specific defaults won't be initialized,
*              which may result in suboptimal default settings (this is
*              important mainly for encoders, e.g. libx264).
*
* @return An AVCodecContext filled with default values or NULL on failure.
*/
AVCodecContext* avcodec_alloc_context3(const AVCodec* codec);

/**
* Free the codec context and everything associated with it and write NULL to
* the provided pointer.
*/
void avcodec_free_context(AVCodecContext** avctx);

/**
* Get the AVClass for AVCodecContext. It can be used in combination with
* AV_OPT_SEARCH_FAKE_OBJ for examining options.
*
* @see av_opt_find().
*/
const AVClass* avcodec_get_class(void);

/**
* Get the AVClass for AVSubtitleRect. It can be used in combination with
* AV_OPT_SEARCH_FAKE_OBJ for examining options.
*
* @see av_opt_find().
*/
const AVClass* avcodec_get_subtitle_rect_class(void);

/**
* Fill the parameters struct based on the values from the supplied codec
* context. Any allocated fields in par are freed and replaced with duplicates
* of the corresponding fields in codec.
*
* @return >= 0 on success, a negative AVERROR code on failure
*/
int avcodec_parameters_from_context(struct AVCodecParameters* par,
                                   const AVCodecContext* codec);

/**
* Fill the codec context based on the values from the supplied codec
* parameters. Any allocated fields in codec that have a corresponding field in
* par are freed and replaced with duplicates of the corresponding field in par.
* Fields in codec that do not have a counterpart in par are not touched.
*
* @return >= 0 on success, a negative AVERROR code on failure.
*/
int avcodec_parameters_to_context(AVCodecContext* codec,
                                 const struct AVCodecParameters* par);

/**
* Initialize the AVCodecContext to use the given AVCodec. Prior to using this
* function the context has to be allocated with avcodec_alloc_context3().
*
* The functions avcodec_find_decoder_by_name(), avcodec_find_encoder_by_name(),
* avcodec_find_decoder() and avcodec_find_encoder() provide an easy way for
* retrieving a codec.
*
* Depending on the codec, you might need to set options in the codec context
* also for decoding (e.g. width, height, or the pixel or audio sample format in
* the case the information is not available in the bitstream, as when decoding
* raw audio or video).
*
* Options in the codec context can be set either by setting them in the options
* AVDictionary, or by setting the values in the context itself, directly or by
* using the av_opt_set() API before calling this function.
*
* Example:
* @code
* av_dict_set(&opts, "b", "2.5M", 0);
* codec = avcodec_find_decoder(AV_CODEC_ID_H264);
* if (!codec)
*     exit(1);
*
* context = avcodec_alloc_context3(codec);
*
* if (avcodec_open2(context, codec, opts) < 0)
*     exit(1);
* @endcode
*
* In the case AVCodecParameters are available (e.g. when demuxing a stream
* using libavformat, and accessing the AVStream contained in the demuxer), the
* codec parameters can be copied to the codec context using
* avcodec_parameters_to_context(), as in the following example:
*
* @code
* AVStream *stream = ...;
* context = avcodec_alloc_context3(codec);
* if (avcodec_parameters_to_context(context, stream->codecpar) < 0)
*     exit(1);
* if (avcodec_open2(context, codec, NULL) < 0)
*     exit(1);
* @endcode
*
* @note Always call this function before using decoding routines (such as
* @ref avcodec_receive_frame()).
*
* @param avctx The context to initialize.
* @param codec The codec to open this context for. If a non-NULL codec has been
*              previously passed to avcodec_alloc_context3() or
*              for this context, then this parameter MUST be either NULL or
*              equal to the previously passed codec.
* @param options A dictionary filled with AVCodecContext and codec-private
*                options, which are set on top of the options already set in
*                avctx, can be NULL. On return this object will be filled with
*                options that were not found in the avctx codec context.
*
* @return zero on success, a negative value on error
* @see avcodec_alloc_context3(), avcodec_find_decoder(),
* avcodec_find_encoder(), av_dict_set(), av_opt_set(), av_opt_find(),
* avcodec_parameters_to_context()
*/
int avcodec_open2(AVCodecContext* avctx, const AVCodec* codec,
                 AVDictionary** options);

#if FF_API_AVCODEC_CLOSE
/**
* Close a given AVCodecContext and free all the data associated with it
* (but not the AVCodecContext itself).
*
* Calling this function on an AVCodecContext that hasn't been opened will free
* the codec-specific data allocated in avcodec_alloc_context3() with a non-NULL
* codec. Subsequent calls will do nothing.
*
* @deprecated Do not use this function. Use avcodec_free_context() to destroy a
* codec context (either open or closed). Opening and closing a codec context
* multiple times is not supported anymore -- use multiple codec contexts
* instead.
*/
attribute_deprecated int avcodec_close(AVCodecContext* avctx);
#endif

/**
* Free all allocated data in the given subtitle struct.
*
* @param sub AVSubtitle to free.
*/
void avsubtitle_free(AVSubtitle* sub);

/**
* @}
*/

/**
* @addtogroup lavc_decoding
* @{
*/

/**
* The default callback for AVCodecContext.get_buffer2(). It is made public so
* it can be called by custom get_buffer2() implementations for decoders without
* AV_CODEC_CAP_DR1 set.
*/
int avcodec_default_get_buffer2(AVCodecContext* s, AVFrame* frame, int flags);

/**
* The default callback for AVCodecContext.get_encode_buffer(). It is made
* public so it can be called by custom get_encode_buffer() implementations for
* encoders without AV_CODEC_CAP_DR1 set.
*/
int avcodec_default_get_encode_buffer(AVCodecContext* s, AVPacket* pkt,
                                     int flags);

/**
* Modify width and height values so that they will result in a memory
* buffer that is acceptable for the codec if you do not use any horizontal
* padding.
*
* May only be used if a codec with AV_CODEC_CAP_DR1 has been opened.
*/
void avcodec_align_dimensions(AVCodecContext* s, int* width, int* height);

/**
* Modify width and height values so that they will result in a memory
* buffer that is acceptable for the codec if you also ensure that all
* line sizes are a multiple of the respective linesize_align[i].
*
* May only be used if a codec with AV_CODEC_CAP_DR1 has been opened.
*/
void avcodec_align_dimensions2(AVCodecContext* s, int* width, int* height,
                              int linesize_align[AV_NUM_DATA_POINTERS]);

/**
* Decode a subtitle message.
* Return a negative value on error, otherwise return the number of bytes used.
* If no subtitle could be decompressed, got_sub_ptr is zero.
* Otherwise, the subtitle is stored in *sub.
* Note that AV_CODEC_CAP_DR1 is not available for subtitle codecs. This is for
* simplicity, because the performance difference is expected to be negligible
* and reusing a get_buffer written for video codecs would probably perform
* badly due to a potentially very different allocation pattern.
*
* Some decoders (those marked with AV_CODEC_CAP_DELAY) have a delay between
* input and output. This means that for some packets they will not immediately
* produce decoded output and need to be flushed at the end of decoding to get
* all the decoded data. Flushing is done by calling this function with packets
* with avpkt->data set to NULL and avpkt->size set to 0 until it stops
* returning subtitles. It is safe to flush even those decoders that are not
* marked with AV_CODEC_CAP_DELAY, then no subtitles will be returned.
*
* @note The AVCodecContext MUST have been opened with @ref avcodec_open2()
* before packets may be fed to the decoder.
*
* @param avctx the codec context
* @param[out] sub The preallocated AVSubtitle in which the decoded subtitle
* will be stored, must be freed with avsubtitle_free if *got_sub_ptr is set.
* @param[in,out] got_sub_ptr Zero if no subtitle could be decompressed,
* otherwise, it is nonzero.
* @param[in] avpkt The input AVPacket containing the input buffer.
*/
int avcodec_decode_subtitle2(AVCodecContext* avctx, AVSubtitle* sub,
                            int* got_sub_ptr, const AVPacket* avpkt);

/**
* Supply raw packet data as input to a decoder.
*
* Internally, this call will copy relevant AVCodecContext fields, which can
* influence decoding per-packet, and apply them when the packet is actually
* decoded. (For example AVCodecContext.skip_frame, which might direct the
* decoder to drop the frame contained by the packet sent with this function.)
*
* @warning The input buffer, avpkt->data must be AV_INPUT_BUFFER_PADDING_SIZE
*          larger than the actual read bytes because some optimized bitstream
*          readers read 32 or 64 bits at once and could read over the end.
*
* @note The AVCodecContext MUST have been opened with @ref avcodec_open2()
*       before packets may be fed to the decoder.
*
* @param avctx codec context
* @param[in] avpkt The input AVPacket. Usually, this will be a single video
*                  frame, or several complete audio frames.
*                  Ownership of the packet remains with the caller, and the
*                  decoder will not write to the packet. The decoder may create
*                  a reference to the packet data (or copy it if the packet is
*                  not reference-counted).
*                  Unlike with older APIs, the packet is always fully consumed,
*                  and if it contains multiple frames (e.g. some audio codecs),
*                  will require you to call avcodec_receive_frame() multiple
*                  times afterwards before you can send a new packet.
*                  It can be NULL (or an AVPacket with data set to NULL and
*                  size set to 0); in this case, it is considered a flush
*                  packet, which signals the end of the stream. Sending the
*                  first flush packet will return success. Subsequent ones are
*                  unnecessary and will return AVERROR_EOF. If the decoder
*                  still has frames buffered, it will return them after sending
*                  a flush packet.
*
* @retval 0                 success
* @retval AVERROR(EAGAIN)   input is not accepted in the current state - user
*                           must read output with avcodec_receive_frame() (once
*                           all output is read, the packet should be resent,
*                           and the call will not fail with EAGAIN).
* @retval AVERROR_EOF       the decoder has been flushed, and no new packets
* can be sent to it (also returned if more than 1 flush packet is sent)
* @retval AVERROR(EINVAL)   codec not opened, it is an encoder, or requires
* flush
* @retval AVERROR(ENOMEM)   failed to add packet to internal queue, or similar
* @retval "another negative error code" legitimate decoding errors
*/
int avcodec_send_packet(AVCodecContext* avctx, const AVPacket* avpkt);

/**
* Return decoded output data from a decoder or encoder (when the
* @ref AV_CODEC_FLAG_RECON_FRAME flag is used).
*
* @param avctx codec context
* @param frame This will be set to a reference-counted video or audio
*              frame (depending on the decoder type) allocated by the
*              codec. Note that the function will always call
*              av_frame_unref(frame) before doing anything else.
*
* @retval 0                success, a frame was returned
* @retval AVERROR(EAGAIN)  output is not available in this state - user must
*                          try to send new input
* @retval AVERROR_EOF      the codec has been fully flushed, and there will be
*                          no more output frames
* @retval AVERROR(EINVAL)  codec not opened, or it is an encoder without the
*                          @ref AV_CODEC_FLAG_RECON_FRAME flag enabled
* @retval "other negative error code" legitimate decoding errors
*/
int avcodec_receive_frame(AVCodecContext* avctx, AVFrame* frame);

/**
* Supply a raw video or audio frame to the encoder. Use
* avcodec_receive_packet() to retrieve buffered output packets.
*
* @param avctx     codec context
* @param[in] frame AVFrame containing the raw audio or video frame to be
* encoded. Ownership of the frame remains with the caller, and the encoder will
* not write to the frame. The encoder may create a reference to the frame data
* (or copy it if the frame is not reference-counted). It can be NULL, in which
* case it is considered a flush packet.  This signals the end of the stream. If
* the encoder still has packets buffered, it will return them after this call.
* Once flushing mode has been entered, additional flush packets are ignored,
* and sending frames will return AVERROR_EOF.
*
*                  For audio:
*                  If AV_CODEC_CAP_VARIABLE_FRAME_SIZE is set, then each frame
*                  can have any number of samples.
*                  If it is not set, frame->nb_samples must be equal to
*                  avctx->frame_size for all frames except the last.
*                  The final frame may be smaller than avctx->frame_size.
* @retval 0                 success
* @retval AVERROR(EAGAIN)   input is not accepted in the current state - user
* must read output with avcodec_receive_packet() (once all output is read, the
* packet should be resent, and the call will not fail with EAGAIN).
* @retval AVERROR_EOF       the encoder has been flushed, and no new frames can
*                           be sent to it
* @retval AVERROR(EINVAL)   codec not opened, it is a decoder, or requires
* flush
* @retval AVERROR(ENOMEM)   failed to add packet to internal queue, or similar
* @retval "another negative error code" legitimate encoding errors
*/
int avcodec_send_frame(AVCodecContext* avctx, const AVFrame* frame);

/**
* Read encoded data from the encoder.
*
* @param avctx codec context
* @param avpkt This will be set to a reference-counted packet allocated by the
*              encoder. Note that the function will always call
*              av_packet_unref(avpkt) before doing anything else.
* @retval 0               success
* @retval AVERROR(EAGAIN) output is not available in the current state - user
* must try to send input
* @retval AVERROR_EOF     the encoder has been fully flushed, and there will be
* no more output packets
* @retval AVERROR(EINVAL) codec not opened, or it is a decoder
* @retval "another negative error code" legitimate encoding errors
*/
int avcodec_receive_packet(AVCodecContext* avctx, AVPacket* avpkt);

/**
* Create and return a AVHWFramesContext with values adequate for hardware
* decoding. This is meant to get called from the get_format callback, and is
* a helper for preparing a AVHWFramesContext for AVCodecContext.hw_frames_ctx.
* This API is for decoding with certain hardware acceleration modes/APIs only.
*
* The returned AVHWFramesContext is not initialized. The caller must do this
* with av_hwframe_ctx_init().
*
* Calling this function is not a requirement, but makes it simpler to avoid
* codec or hardware API specific details when manually allocating frames.
*
* Alternatively to this, an API user can set AVCodecContext.hw_device_ctx,
* which sets up AVCodecContext.hw_frames_ctx fully automatically, and makes
* it unnecessary to call this function or having to care about
* AVHWFramesContext initialization at all.
*
* There are a number of requirements for calling this function:
*
* - It must be called from get_format with the same avctx parameter that was
*   passed to get_format. Calling it outside of get_format is not allowed, and
*   can trigger undefined behavior.
* - The function is not always supported (see description of return values).
*   Even if this function returns successfully, hwaccel initialization could
*   fail later. (The degree to which implementations check whether the stream
*   is actually supported varies. Some do this check only after the user's
*   get_format callback returns.)
* - The hw_pix_fmt must be one of the choices suggested by get_format. If the
*   user decides to use a AVHWFramesContext prepared with this API function,
*   the user must return the same hw_pix_fmt from get_format.
* - The device_ref passed to this function must support the given hw_pix_fmt.
* - After calling this API function, it is the user's responsibility to
*   initialize the AVHWFramesContext (returned by the out_frames_ref
* parameter), and to set AVCodecContext.hw_frames_ctx to it. If done, this must
* be done before returning from get_format (this is implied by the normal
*   AVCodecContext.hw_frames_ctx API rules).
* - The AVHWFramesContext parameters may change every time time get_format is
*   called. Also, AVCodecContext.hw_frames_ctx is reset before get_format. So
*   you are inherently required to go through this process again on every
*   get_format call.
* - It is perfectly possible to call this function without actually using
*   the resulting AVHWFramesContext. One use-case might be trying to reuse a
*   previously initialized AVHWFramesContext, and calling this API function
*   only to test whether the required frame parameters have changed.
* - Fields that use dynamically allocated values of any kind must not be set
*   by the user unless setting them is explicitly allowed by the documentation.
*   If the user sets AVHWFramesContext.free and AVHWFramesContext.user_opaque,
*   the new free callback must call the potentially set previous free callback.
*   This API call may set any dynamically allocated fields, including the free
*   callback.
*
* The function will set at least the following fields on AVHWFramesContext
* (potentially more, depending on hwaccel API):
*
* - All fields set by av_hwframe_ctx_alloc().
* - Set the format field to hw_pix_fmt.
* - Set the sw_format field to the most suited and most versatile format. (An
*   implication is that this will prefer generic formats over opaque formats
*   with arbitrary restrictions, if possible.)
* - Set the width/height fields to the coded frame size, rounded up to the
*   API-specific minimum alignment.
* - Only _if_ the hwaccel requires a pre-allocated pool: set the
* initial_pool_size field to the number of maximum reference surfaces possible
* with the codec, plus 1 surface for the user to work (meaning the user can
* safely reference at most 1 decoded surface at a time), plus additional
* buffering introduced by frame threading. If the hwaccel does not require
* pre-allocation, the field is left to 0, and the decoder will allocate new
* surfaces on demand during decoding.
* - Possibly AVHWFramesContext.hwctx fields, depending on the underlying
*   hardware API.
*
* Essentially, out_frames_ref returns the same as av_hwframe_ctx_alloc(), but
* with basic frame parameters set.
*
* The function is stateless, and does not change the AVCodecContext or the
* device_ref AVHWDeviceContext.
*
* @param avctx The context which is currently calling get_format, and which
*              implicitly contains all state needed for filling the returned
*              AVHWFramesContext properly.
* @param device_ref A reference to the AVHWDeviceContext describing the device
*                   which will be used by the hardware decoder.
* @param hw_pix_fmt The hwaccel format you are going to return from get_format.
* @param out_frames_ref On success, set to a reference to an _uninitialized_
*                       AVHWFramesContext, created from the given device_ref.
*                       Fields will be set to values required for decoding.
*                       Not changed if an error is returned.
* @return zero on success, a negative value on error. The following error codes
*         have special semantics:
*      AVERROR(ENOENT): the decoder does not support this functionality. Setup
*                       is always manual, or it is a decoder which does not
*                       support setting AVCodecContext.hw_frames_ctx at all,
*                       or it is a software format.
*      AVERROR(EINVAL): it is known that hardware decoding is not supported for
*                       this configuration, or the device_ref is not supported
*                       for the hwaccel referenced by hw_pix_fmt.
*/
int avcodec_get_hw_frames_parameters(AVCodecContext* avctx,
                                    AVBufferRef* device_ref,
                                    enum AVPixelFormat hw_pix_fmt,
                                    AVBufferRef** out_frames_ref);

/**
* @defgroup lavc_parsing Frame parsing
* @{
*/

enum AVPictureStructure {
 AV_PICTURE_STRUCTURE_UNKNOWN,       ///< unknown
 AV_PICTURE_STRUCTURE_TOP_FIELD,     ///< coded as top field
 AV_PICTURE_STRUCTURE_BOTTOM_FIELD,  ///< coded as bottom field
 AV_PICTURE_STRUCTURE_FRAME,         ///< coded as frame
};

typedef struct AVCodecParserContext {
 void* priv_data;
 const struct AVCodecParser* parser;
 int64_t frame_offset;      /* offset of the current frame */
 int64_t cur_offset;        /* current offset
                               (incremented by each av_parser_parse()) */
 int64_t next_frame_offset; /* offset of the next frame */
 /* video info */
 int pict_type; /* XXX: Put it back in AVCodecContext. */
 /**
  * This field is used for proper frame duration computation in lavf.
  * It signals, how much longer the frame duration of the current frame
  * is compared to normal frame duration.
  *
  * frame_duration = (1 + repeat_pict) * time_base
  *
  * It is used by codecs like H.264 to display telecined material.
  */
 int repeat_pict; /* XXX: Put it back in AVCodecContext. */
 int64_t pts;     /* pts of the current frame */
 int64_t dts;     /* dts of the current frame */

 /* private data */
 int64_t last_pts;
 int64_t last_dts;
 int fetch_timestamp;

#define AV_PARSER_PTS_NB 4
 int cur_frame_start_index;
 int64_t cur_frame_offset[AV_PARSER_PTS_NB];
 int64_t cur_frame_pts[AV_PARSER_PTS_NB];
 int64_t cur_frame_dts[AV_PARSER_PTS_NB];

 int flags;
#define PARSER_FLAG_COMPLETE_FRAMES 0x0001
#define PARSER_FLAG_ONCE 0x0002
/// Set if the parser has a valid file offset
#define PARSER_FLAG_FETCHED_OFFSET 0x0004
#define PARSER_FLAG_USE_CODEC_TS 0x1000

 int64_t offset;  ///< byte offset from starting packet start
 int64_t cur_frame_end[AV_PARSER_PTS_NB];

 /**
  * Set by parser to 1 for key frames and 0 for non-key frames.
  * It is initialized to -1, so if the parser doesn't set this flag,
  * old-style fallback using AV_PICTURE_TYPE_I picture type as key frames
  * will be used.
  */
 int key_frame;

 // Timestamp generation support:
 /**
  * Synchronization point for start of timestamp generation.
  *
  * Set to >0 for sync point, 0 for no sync point and <0 for undefined
  * (default).
  *
  * For example, this corresponds to presence of H.264 buffering period
  * SEI message.
  */
 int dts_sync_point;

 /**
  * Offset of the current timestamp against last timestamp sync point in
  * units of AVCodecContext.time_base.
  *
  * Set to INT_MIN when dts_sync_point unused. Otherwise, it must
  * contain a valid timestamp offset.
  *
  * Note that the timestamp of sync point has usually a nonzero
  * dts_ref_dts_delta, which refers to the previous sync point. Offset of
  * the next frame after timestamp sync point will be usually 1.
  *
  * For example, this corresponds to H.264 cpb_removal_delay.
  */
 int dts_ref_dts_delta;

 /**
  * Presentation delay of current frame in units of AVCodecContext.time_base.
  *
  * Set to INT_MIN when dts_sync_point unused. Otherwise, it must
  * contain valid non-negative timestamp delta (presentation time of a frame
  * must not lie in the past).
  *
  * This delay represents the difference between decoding and presentation
  * time of the frame.
  *
  * For example, this corresponds to H.264 dpb_output_delay.
  */
 int pts_dts_delta;

 /**
  * Position of the packet in file.
  *
  * Analogous to cur_frame_pts/dts
  */
 int64_t cur_frame_pos[AV_PARSER_PTS_NB];

 /**
  * Byte position of currently parsed frame in stream.
  */
 int64_t pos;

 /**
  * Previous frame byte position.
  */
 int64_t last_pos;

 /**
  * Duration of the current frame.
  * For audio, this is in units of 1 / AVCodecContext.sample_rate.
  * For all other types, this is in units of AVCodecContext.time_base.
  */
 int duration;

 enum AVFieldOrder field_order;

 /**
  * Indicate whether a picture is coded as a frame, top field or bottom field.
  *
  * For example, H.264 field_pic_flag equal to 0 corresponds to
  * AV_PICTURE_STRUCTURE_FRAME. An H.264 picture with field_pic_flag
  * equal to 1 and bottom_field_flag equal to 0 corresponds to
  * AV_PICTURE_STRUCTURE_TOP_FIELD.
  */
 enum AVPictureStructure picture_structure;

 /**
  * Picture number incremented in presentation or output order.
  * This field may be reinitialized at the first picture of a new sequence.
  *
  * For example, this corresponds to H.264 PicOrderCnt.
  */
 int output_picture_number;

 /**
  * Dimensions of the decoded video intended for presentation.
  */
 int width;
 int height;

 /**
  * Dimensions of the coded video.
  */
 int coded_width;
 int coded_height;

 /**
  * The format of the coded data, corresponds to enum AVPixelFormat for video
  * and for enum AVSampleFormat for audio.
  *
  * Note that a decoder can have considerable freedom in how exactly it
  * decodes the data, so the format reported here might be different from the
  * one returned by a decoder.
  */
 int format;
} AVCodecParserContext;

typedef struct AVCodecParser {
 int codec_ids[7]; /* several codec IDs are permitted */
 int priv_data_size;
 int (*parser_init)(AVCodecParserContext* s);
 /* This callback never returns an error, a negative value means that
  * the frame start was in a previous packet. */
 int (*parser_parse)(AVCodecParserContext* s, AVCodecContext* avctx,
                     const uint8_t** poutbuf, int* poutbuf_size,
                     const uint8_t* buf, int buf_size);
 void (*parser_close)(AVCodecParserContext* s);
 int (*split)(AVCodecContext* avctx, const uint8_t* buf, int buf_size);
} AVCodecParser;

/**
* Iterate over all registered codec parsers.
*
* @param opaque a pointer where libavcodec will store the iteration state. Must
*               point to NULL to start the iteration.
*
* @return the next registered codec parser or NULL when the iteration is
*         finished
*/
const AVCodecParser* av_parser_iterate(void** opaque);

AVCodecParserContext* av_parser_init(int codec_id);

/**
* Parse a packet.
*
* @param s             parser context.
* @param avctx         codec context.
* @param poutbuf       set to pointer to parsed buffer or NULL if not yet
finished.
* @param poutbuf_size  set to size of parsed buffer or zero if not yet
finished.
* @param buf           input buffer.
* @param buf_size      buffer size in bytes without the padding. I.e. the full
buffer size is assumed to be buf_size + AV_INPUT_BUFFER_PADDING_SIZE. To signal
EOF, this should be 0 (so that the last frame can be output).
* @param pts           input presentation timestamp.
* @param dts           input decoding timestamp.
* @param pos           input byte position in stream.
* @return the number of bytes of the input bitstream used.
*
* Example:
* @code
*   while(in_len){
*       len = av_parser_parse2(myparser, AVCodecContext, &data, &size,
*                                        in_data, in_len,
*                                        pts, dts, pos);
*       in_data += len;
*       in_len  -= len;
*
*       if(size)
*          decode_frame(data, size);
*   }
* @endcode
*/
int av_parser_parse2(AVCodecParserContext* s, AVCodecContext* avctx,
                    uint8_t** poutbuf, int* poutbuf_size, const uint8_t* buf,
                    int buf_size, int64_t pts, int64_t dts, int64_t pos);

void av_parser_close(AVCodecParserContext* s);

/**
* @}
* @}
*/

/**
* @addtogroup lavc_encoding
* @{
*/

int avcodec_encode_subtitle(AVCodecContext* avctx, uint8_t* buf, int buf_size,
                           const AVSubtitle* sub);

/**
* @}
*/

/**
* @defgroup lavc_misc Utility functions
* @ingroup libavc
*
* Miscellaneous utility functions related to both encoding and decoding
* (or neither).
* @{
*/

/**
* @defgroup lavc_misc_pixfmt Pixel formats
*
* Functions for working with pixel formats.
* @{
*/

/**
* Return a value representing the fourCC code associated to the
* pixel format pix_fmt, or 0 if no associated fourCC code can be
* found.
*/
unsigned int avcodec_pix_fmt_to_codec_tag(enum AVPixelFormat pix_fmt);

/**
* Find the best pixel format to convert to given a certain source pixel
* format.  When converting from one pixel format to another, information loss
* may occur.  For example, when converting from RGB24 to GRAY, the color
* information will be lost. Similarly, other losses occur when converting from
* some formats to other formats. avcodec_find_best_pix_fmt_of_2() searches
* which of the given pixel formats should be used to suffer the least amount of
* loss. The pixel formats from which it chooses one, are determined by the
* pix_fmt_list parameter.
*
*
* @param[in] pix_fmt_list AV_PIX_FMT_NONE terminated array of pixel formats to
* choose from
* @param[in] src_pix_fmt source pixel format
* @param[in] has_alpha Whether the source pixel format alpha channel is used.
* @param[out] loss_ptr Combination of flags informing you what kind of losses
* will occur.
* @return The best pixel format to convert to or -1 if none was found.
*/
enum AVPixelFormat avcodec_find_best_pix_fmt_of_list(
   const enum AVPixelFormat* pix_fmt_list, enum AVPixelFormat src_pix_fmt,
   int has_alpha, int* loss_ptr);

enum AVPixelFormat avcodec_default_get_format(struct AVCodecContext* s,
                                             const enum AVPixelFormat* fmt);

/**
* @}
*/

void avcodec_string(char* buf, int buf_size, AVCodecContext* enc, int encode);

int avcodec_default_execute(AVCodecContext* c,
                           int (*func)(AVCodecContext* c2, void* arg2),
                           void* arg, int* ret, int count, int size);
int avcodec_default_execute2(AVCodecContext* c,
                            int (*func)(AVCodecContext* c2, void* arg2, int,
                                        int),
                            void* arg, int* ret, int count);
// FIXME func typedef

/**
* Fill AVFrame audio data and linesize pointers.
*
* The buffer buf must be a preallocated buffer with a size big enough
* to contain the specified samples amount. The filled AVFrame data
* pointers will point to this buffer.
*
* AVFrame extended_data channel pointers are allocated if necessary for
* planar audio.
*
* @param frame       the AVFrame
*                    frame->nb_samples must be set prior to calling the
*                    function. This function fills in frame->data,
*                    frame->extended_data, frame->linesize[0].
* @param nb_channels channel count
* @param sample_fmt  sample format
* @param buf         buffer to use for frame data
* @param buf_size    size of buffer
* @param align       plane size sample alignment (0 = default)
* @return            >=0 on success, negative error code on failure
* @todo return the size in bytes required to store the samples in
* case of success, at the next libavutil bump
*/
int avcodec_fill_audio_frame(AVFrame* frame, int nb_channels,
                            enum AVSampleFormat sample_fmt, const uint8_t* buf,
                            int buf_size, int align);

/**
* Reset the internal codec state / flush internal buffers. Should be called
* e.g. when seeking or when switching to a different stream.
*
* @note for decoders, this function just releases any references the decoder
* might keep internally, but the caller's references remain valid.
*
* @note for encoders, this function will only do something if the encoder
* declares support for AV_CODEC_CAP_ENCODER_FLUSH. When called, the encoder
* will drain any remaining packets, and can then be re-used for a different
* stream (as opposed to sending a null frame which will leave the encoder
* in a permanent EOF state after draining). This can be desirable if the
* cost of tearing down and replacing the encoder instance is high.
*/
void avcodec_flush_buffers(AVCodecContext* avctx);

/**
* Return audio frame duration.
*
* @param avctx        codec context
* @param frame_bytes  size of the frame, or 0 if unknown
* @return             frame duration, in samples, if known. 0 if not able to
*                     determine.
*/
int av_get_audio_frame_duration(AVCodecContext* avctx, int frame_bytes);

/* memory */

/**
* Same behaviour av_fast_malloc but the buffer has additional
* AV_INPUT_BUFFER_PADDING_SIZE at the end which will always be 0.
*
* In addition the whole buffer will initially and after resizes
* be 0-initialized so that no uninitialized data will ever appear.
*/
void av_fast_padded_malloc(void* ptr, unsigned int* size, size_t min_size);

/**
* Same behaviour av_fast_padded_malloc except that buffer will always
* be 0-initialized after call.
*/
void av_fast_padded_mallocz(void* ptr, unsigned int* size, size_t min_size);

/**
* @return a positive value if s is open (i.e. avcodec_open2() was called on it
* with no corresponding avcodec_close()), 0 otherwise.
*/
int avcodec_is_open(AVCodecContext* s);

/**
* @}
*/

#endif /* AVCODEC_AVCODEC_H */