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bsf.h (11420B)

---

/*
* Bitstream filters public API
*
* 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_BSF_H
#define AVCODEC_BSF_H

#include "libavutil/dict.h"
#include "libavutil/log.h"
#include "libavutil/rational.h"

#include "codec_id.h"
#include "codec_par.h"
#include "packet.h"

/**
* @defgroup lavc_bsf Bitstream filters
* @ingroup libavc
*
* Bitstream filters transform encoded media data without decoding it. This
* allows e.g. manipulating various header values. Bitstream filters operate on
* @ref AVPacket "AVPackets".
*
* The bitstream filtering API is centered around two structures:
* AVBitStreamFilter and AVBSFContext. The former represents a bitstream filter
* in abstract, the latter a specific filtering process. Obtain an
* AVBitStreamFilter using av_bsf_get_by_name() or av_bsf_iterate(), then pass
* it to av_bsf_alloc() to create an AVBSFContext. Fill in the user-settable
* AVBSFContext fields, as described in its documentation, then call
* av_bsf_init() to prepare the filter context for use.
*
* Submit packets for filtering using av_bsf_send_packet(), obtain filtered
* results with av_bsf_receive_packet(). When no more input packets will be
* sent, submit a NULL AVPacket to signal the end of the stream to the filter.
* av_bsf_receive_packet() will then return trailing packets, if any are
* produced by the filter.
*
* Finally, free the filter context with av_bsf_free().
* @{
*/

/**
* The bitstream filter state.
*
* This struct must be allocated with av_bsf_alloc() and freed with
* av_bsf_free().
*
* The fields in the struct will only be changed (by the caller or by the
* filter) as described in their documentation, and are to be considered
* immutable otherwise.
*/
typedef struct AVBSFContext {
 /**
  * A class for logging and AVOptions
  */
 const AVClass* av_class;

 /**
  * The bitstream filter this context is an instance of.
  */
 const struct AVBitStreamFilter* filter;

 /**
  * Opaque filter-specific private data. If filter->priv_class is non-NULL,
  * this is an AVOptions-enabled struct.
  */
 void* priv_data;

 /**
  * Parameters of the input stream. This field is allocated in
  * av_bsf_alloc(), it needs to be filled by the caller before
  * av_bsf_init().
  */
 AVCodecParameters* par_in;

 /**
  * Parameters of the output stream. This field is allocated in
  * av_bsf_alloc(), it is set by the filter in av_bsf_init().
  */
 AVCodecParameters* par_out;

 /**
  * The timebase used for the timestamps of the input packets. Set by the
  * caller before av_bsf_init().
  */
 AVRational time_base_in;

 /**
  * The timebase used for the timestamps of the output packets. Set by the
  * filter in av_bsf_init().
  */
 AVRational time_base_out;
} AVBSFContext;

typedef struct AVBitStreamFilter {
 const char* name;

 /**
  * A list of codec ids supported by the filter, terminated by
  * AV_CODEC_ID_NONE.
  * May be NULL, in that case the bitstream filter works with any codec id.
  */
 const enum AVCodecID* codec_ids;

 /**
  * A class for the private data, used to declare bitstream filter private
  * AVOptions. This field is NULL for bitstream filters that do not declare
  * any options.
  *
  * If this field is non-NULL, the first member of the filter private data
  * must be a pointer to AVClass, which will be set by libavcodec generic
  * code to this class.
  */
 const AVClass* priv_class;
} AVBitStreamFilter;

/**
* @return a bitstream filter with the specified name or NULL if no such
*         bitstream filter exists.
*/
const AVBitStreamFilter* av_bsf_get_by_name(const char* name);

/**
* Iterate over all registered bitstream filters.
*
* @param opaque a pointer where libavcodec will store the iteration state. Must
*               point to NULL to start the iteration.
*
* @return the next registered bitstream filter or NULL when the iteration is
*         finished
*/
const AVBitStreamFilter* av_bsf_iterate(void** opaque);

/**
* Allocate a context for a given bitstream filter. The caller must fill in the
* context parameters as described in the documentation and then call
* av_bsf_init() before sending any data to the filter.
*
* @param filter the filter for which to allocate an instance.
* @param[out] ctx a pointer into which the pointer to the newly-allocated
* context will be written. It must be freed with av_bsf_free() after the
*                 filtering is done.
*
* @return 0 on success, a negative AVERROR code on failure
*/
int av_bsf_alloc(const AVBitStreamFilter* filter, AVBSFContext** ctx);

/**
* Prepare the filter for use, after all the parameters and options have been
* set.
*
* @param ctx a AVBSFContext previously allocated with av_bsf_alloc()
*/
int av_bsf_init(AVBSFContext* ctx);

/**
* Submit a packet for filtering.
*
* After sending each packet, the filter must be completely drained by calling
* av_bsf_receive_packet() repeatedly until it returns AVERROR(EAGAIN) or
* AVERROR_EOF.
*
* @param ctx an initialized AVBSFContext
* @param pkt the packet to filter. The bitstream filter will take ownership of
* the packet and reset the contents of pkt. pkt is not touched if an error
* occurs. If pkt is empty (i.e. NULL, or pkt->data is NULL and
* pkt->side_data_elems zero), it signals the end of the stream (i.e. no more
* non-empty packets will be sent; sending more empty packets does nothing) and
* will cause the filter to output any packets it may have buffered internally.
*
* @return
*  - 0 on success.
*  - AVERROR(EAGAIN) if packets need to be retrieved from the filter (using
*    av_bsf_receive_packet()) before new input can be consumed.
*  - Another negative AVERROR value if an error occurs.
*/
int av_bsf_send_packet(AVBSFContext* ctx, AVPacket* pkt);

/**
* Retrieve a filtered packet.
*
* @param ctx an initialized AVBSFContext
* @param[out] pkt this struct will be filled with the contents of the filtered
*                 packet. It is owned by the caller and must be freed using
*                 av_packet_unref() when it is no longer needed.
*                 This parameter should be "clean" (i.e. freshly allocated
*                 with av_packet_alloc() or unreffed with av_packet_unref())
*                 when this function is called. If this function returns
*                 successfully, the contents of pkt will be completely
*                 overwritten by the returned data. On failure, pkt is not
*                 touched.
*
* @return
*  - 0 on success.
*  - AVERROR(EAGAIN) if more packets need to be sent to the filter (using
*    av_bsf_send_packet()) to get more output.
*  - AVERROR_EOF if there will be no further output from the filter.
*  - Another negative AVERROR value if an error occurs.
*
* @note one input packet may result in several output packets, so after sending
* a packet with av_bsf_send_packet(), this function needs to be called
* repeatedly until it stops returning 0. It is also possible for a filter to
* output fewer packets than were sent to it, so this function may return
* AVERROR(EAGAIN) immediately after a successful av_bsf_send_packet() call.
*/
int av_bsf_receive_packet(AVBSFContext* ctx, AVPacket* pkt);

/**
* Reset the internal bitstream filter state. Should be called e.g. when
* seeking.
*/
void av_bsf_flush(AVBSFContext* ctx);

/**
* Free a bitstream filter context and everything associated with it; write NULL
* into the supplied pointer.
*/
void av_bsf_free(AVBSFContext** ctx);

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

/**
* Structure for chain/list of bitstream filters.
* Empty list can be allocated by av_bsf_list_alloc().
*/
typedef struct AVBSFList AVBSFList;

/**
* Allocate empty list of bitstream filters.
* The list must be later freed by av_bsf_list_free()
* or finalized by av_bsf_list_finalize().
*
* @return Pointer to @ref AVBSFList on success, NULL in case of failure
*/
AVBSFList* av_bsf_list_alloc(void);

/**
* Free list of bitstream filters.
*
* @param lst Pointer to pointer returned by av_bsf_list_alloc()
*/
void av_bsf_list_free(AVBSFList** lst);

/**
* Append bitstream filter to the list of bitstream filters.
*
* @param lst List to append to
* @param bsf Filter context to be appended
*
* @return >=0 on success, negative AVERROR in case of failure
*/
int av_bsf_list_append(AVBSFList* lst, AVBSFContext* bsf);

/**
* Construct new bitstream filter context given it's name and options
* and append it to the list of bitstream filters.
*
* @param lst      List to append to
* @param bsf_name Name of the bitstream filter
* @param options  Options for the bitstream filter, can be set to NULL
*
* @return >=0 on success, negative AVERROR in case of failure
*/
int av_bsf_list_append2(AVBSFList* lst, const char* bsf_name,
                       AVDictionary** options);
/**
* Finalize list of bitstream filters.
*
* This function will transform @ref AVBSFList to single @ref AVBSFContext,
* so the whole chain of bitstream filters can be treated as single filter
* freshly allocated by av_bsf_alloc().
* If the call is successful, @ref AVBSFList structure is freed and lst
* will be set to NULL. In case of failure, caller is responsible for
* freeing the structure by av_bsf_list_free()
*
* @param      lst Filter list structure to be transformed
* @param[out] bsf Pointer to be set to newly created @ref AVBSFContext
* structure representing the chain of bitstream filters
*
* @return >=0 on success, negative AVERROR in case of failure
*/
int av_bsf_list_finalize(AVBSFList** lst, AVBSFContext** bsf);

/**
* Parse string describing list of bitstream filters and create single
* @ref AVBSFContext describing the whole chain of bitstream filters.
* Resulting @ref AVBSFContext can be treated as any other @ref AVBSFContext
* freshly allocated by av_bsf_alloc().
*
* @param      str String describing chain of bitstream filters in format
*                 `bsf1[=opt1=val1:opt2=val2][,bsf2]`
* @param[out] bsf Pointer to be set to newly created @ref AVBSFContext
* structure representing the chain of bitstream filters
*
* @return >=0 on success, negative AVERROR in case of failure
*/
int av_bsf_list_parse_str(const char* str, AVBSFContext** bsf);

/**
* Get null/pass-through bitstream filter.
*
* @param[out] bsf Pointer to be set to new instance of pass-through bitstream
* filter
*
* @return
*/
int av_bsf_get_null_filter(AVBSFContext** bsf);

/**
* @}
*/

#endif  // AVCODEC_BSF_H