SRS 支持 HEVC 编码

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2023-12-01

SRS哪些协议支持hevc编码

支持hevc编码的协议：

rtmp
httpflv
hls
srt: 具体见srt codec wiki

FLV视频头信息

因为rtmp在2012年后，协议没有更新，对hevc编码格式的支持在rtmp协议官方文档中没有明确定义。
国内cdn厂商通过修改<video>中CodecID的定义，将flv中的hevc codecid定义为12。

Field	Type	Comment
Frame Type	UB [4]	Frame Type Type of video frame. The following values are defined: 1 = key frame (for AVC and HEVC, a seekable frame) 2 = inter frame (for AVC and HEVC, a non-seekable frame) 3 = disposable inter frame (H.263 only) 4 = generated key frame (reserved for server use only) 5 = video info/command frame
CodecID	UB [4]	Codec Identifier. The following values are defined: 2 = Sorenson H.263 3 = Screen video 4 = On2 VP6 5 = On2 VP6 with alpha channel 6 = Screen video version 2 7 = AVC 12=HEVC
HVCPacketType	IF CodecID == 12 UI8	The following values are defined: 0 = HEVC sequence header 1 = HEVC NALU 2 = HEVC end of sequence (lower level NALU sequence ender is not required or supported
CompositionTime	IF CodecID==7 OR CodecID == 12 SI24	IF AVCPacketType == 1 OR HVCPacketType == 1 Composition time offset ELSE 0 See ISO 14496-12, 8.15.3 for an explanation of composition times. The offset in an FLV file is always in milliseconds.
VideoTagBody	IF FrameType == 5 UI8 ELSE ( IF CodecID == 2 H263VIDEOPACKET IF CodecID == 3 SCREENVIDEOPACKET IF CodecID == 4 VP6FLVVIDEOPACKET IF CodecID == 5 VP6FLVALPHAVIDEOPACKET IF CodecID == 6 SCREENV2VIDEOPACKET IF CodecID == 7 AVCVIDEOPACKET IF CodecID == 12 HVCVIDEOPACKET )	Video frame payload or frame info If FrameType == 5, instead of a video payload, the Video Data Body contains a UI8 with the following meaning: 0 = Start of client-side seeking video frame sequence 1 = End of client-side seeking video frame sequence For all but AVCVIDEOPACKET or HVCVIDEOPACKET, see the SWF File Format Specification for details

如何rtmp推/拉流编码格式hevc

因为当前官方ffmpeg的rtmp推/拉流默认不支持hevc的编码，所以需要重新对ffmpeg进行hevc in flv的自定义修改。
需要修改3个文件即可：

libavformat/flv.h 新增hevc类型定义：

enum {
  FLV_CODECID_H263    = 2,
  FLV_CODECID_SCREEN  = 3,
  FLV_CODECID_VP6     = 4,
  FLV_CODECID_VP6A    = 5,
  FLV_CODECID_SCREEN2 = 6,
  FLV_CODECID_H264    = 7,
  FLV_CODECID_REALH263= 8,
  FLV_CODECID_MPEG4   = 9,
  FLV_CODECID_HEVC    = 12,
};

libavformat/flvdec.c
支持hevc编码的flv解封装
libavformat/flvenc.c
支持hevc编码的flv封装

如何编译支持hevc in flv的ffmpeg，请参考ffmpeg supports hevc in flv

如何rtmp推/拉流hevc示例

在完成支持hevc in flv的定制化ffmpeg编译后，rtmp推流hevc视频编码，如下:

ffmpeg -re -i source.flv -c:v libx265 -c:a copy -f flv rtmp://127.0.0.1/live/livestream

rtmp拉流hevc视频编码格式，如下：

ffmpeg -i rtmp://127.0.0.1/live/livestream -f flv -y livestream.flv

播放：

ffplay rtmp://127.0.0.1/live/livestream