h264_decoder_impl.h (3913B)
1 /* 2 * Copyright (c) 2015 The WebRTC project authors. All Rights Reserved. 3 * 4 * Use of this source code is governed by a BSD-style license 5 * that can be found in the LICENSE file in the root of the source 6 * tree. An additional intellectual property rights grant can be found 7 * in the file PATENTS. All contributing project authors may 8 * be found in the AUTHORS file in the root of the source tree. 9 * 10 */ 11 12 #ifndef MODULES_VIDEO_CODING_CODECS_H264_H264_DECODER_IMPL_H_ 13 #define MODULES_VIDEO_CODING_CODECS_H264_H264_DECODER_IMPL_H_ 14 15 // Everything declared in this header is only required when WebRTC is 16 // build with H264 support, please do not move anything out of the 17 // #ifdef unless needed and tested. 18 #ifdef WEBRTC_USE_H264 19 20 #if defined(WEBRTC_WIN) && !defined(__clang__) 21 #error "See: bugs.webrtc.org/9213#c13." 22 #endif 23 24 // CAVEAT: According to ffmpeg docs for avcodec_send_packet, ffmpeg requires a 25 // few extra padding bytes after the end of input. And in addition, docs for 26 // AV_INPUT_BUFFER_PADDING_SIZE says "If the first 23 bits of the additional 27 // bytes are not 0, then damaged MPEG bitstreams could cause overread and 28 // segfault." 29 // 30 // WebRTC doesn't ensure any such padding, and REQUIRES ffmpeg to be compiled 31 // with CONFIG_SAFE_BITSTREAM_READER, which is intended to eliminate 32 // out-of-bounds reads. ffmpeg docs doesn't say explicitly what effects this 33 // flag has on the h.264 decoder or avcodec_send_packet, though, so this is in 34 // some way depending on undocumented behavior. If any problems turn up, we may 35 // have to add an extra copy operation, to enforce padding before buffers are 36 // passed to ffmpeg. 37 extern "C" { 38 #include <libavcodec/avcodec.h> 39 } // extern "C" 40 41 #include <cstdint> 42 #include <memory> 43 44 #include "api/video/encoded_image.h" 45 #include "api/video_codecs/video_decoder.h" 46 #include "common_video/h264/h264_bitstream_parser.h" 47 #include "common_video/include/video_frame_buffer_pool.h" 48 #include "modules/video_coding/codecs/h264/include/h264.h" 49 50 namespace webrtc { 51 52 struct AVCodecContextDeleter { 53 void operator()(AVCodecContext* ptr) const { avcodec_free_context(&ptr); } 54 }; 55 struct AVFrameDeleter { 56 void operator()(AVFrame* ptr) const { av_frame_free(&ptr); } 57 }; 58 59 class H264DecoderImpl : public H264Decoder { 60 public: 61 H264DecoderImpl(); 62 ~H264DecoderImpl() override; 63 64 bool Configure(const Settings& settings) override; 65 int32_t Release() override; 66 67 int32_t RegisterDecodeCompleteCallback( 68 DecodedImageCallback* callback) override; 69 70 // `missing_frames`, `fragmentation` and `render_time_ms` are ignored. 71 int32_t Decode(const EncodedImage& input_image, 72 bool /*missing_frames*/, 73 int64_t render_time_ms = -1) override; 74 75 const char* ImplementationName() const override; 76 77 private: 78 // Called by FFmpeg when it needs a frame buffer to store decoded frames in. 79 // The `VideoFrame` returned by FFmpeg at `Decode` originate from here. Their 80 // buffers are reference counted and freed by FFmpeg using `AVFreeBuffer2`. 81 static int AVGetBuffer2(AVCodecContext* context, 82 AVFrame* av_frame, 83 int flags); 84 // Called by FFmpeg when it is done with a video frame, see `AVGetBuffer2`. 85 static void AVFreeBuffer2(void* opaque, uint8_t* data); 86 87 bool IsInitialized() const; 88 89 // Reports statistics with histograms. 90 void ReportInit(); 91 void ReportError(); 92 93 // Used by ffmpeg via `AVGetBuffer2()` to allocate I420 images. 94 VideoFrameBufferPool ffmpeg_buffer_pool_; 95 std::unique_ptr<AVCodecContext, AVCodecContextDeleter> av_context_; 96 std::unique_ptr<AVFrame, AVFrameDeleter> av_frame_; 97 98 DecodedImageCallback* decoded_image_callback_; 99 100 bool has_reported_init_; 101 bool has_reported_error_; 102 103 H264BitstreamParser h264_bitstream_parser_; 104 }; 105 106 } // namespace webrtc 107 108 #endif // WEBRTC_USE_H264 109 110 #endif // MODULES_VIDEO_CODING_CODECS_H264_H264_DECODER_IMPL_H_