流媒体分析之srt协议ffmpeg 实现

srt  音视频数据是基于mpegts 封装的,ffmpeg 数据流程

1. mpegts    封装格式会后面系列文章中讲叙，在ffmpeg 中的封装实现接口如下：mpegtsenc.c

AVOutputFormat ff_mpegts_muxer = {
    .name           = "mpegts",
    .long_name      = NULL_IF_CONFIG_SMALL("MPEG-TS (MPEG-2 Transport Stream)"),
    .mime_type      = "video/MP2T",
    .extensions     = "ts,m2t,m2ts,mts",
    .priv_data_size = sizeof(MpegTSWrite),
    .audio_codec    = AV_CODEC_ID_MP2,
    .video_codec    = AV_CODEC_ID_MPEG2VIDEO,
    .init           = mpegts_init,
    .write_packet   = mpegts_write_packet,
    .write_trailer  = mpegts_write_end,
    .deinit         = mpegts_deinit,
    .check_bitstream = mpegts_check_bitstream,
    .flags          = AVFMT_ALLOW_FLUSH | AVFMT_VARIABLE_FPS | AVFMT_NODIMENSIONS,
    .priv_class     = &mpegts_muxer_class,
};

解封封装：FFmpeg-n4.3.3/libavformat/mpegts.c

AVInputFormat ff_mpegts_demuxer = {
    .name           = "mpegts",
    .long_name      = NULL_IF_CONFIG_SMALL("MPEG-TS (MPEG-2 Transport Stream)"),
    .priv_data_size = sizeof(MpegTSContext),
    .read_probe     = mpegts_probe,
    .read_header    = mpegts_read_header,
    .read_packet    = mpegts_read_packet,
    .read_close     = mpegts_read_close,
    .read_timestamp = mpegts_get_dts,
    .flags          = AVFMT_SHOW_IDS | AVFMT_TS_DISCONT,
    .priv_class     = &mpegts_class,
};

srt  协议实现： ffmpeg 主要调用libsrt 实现srt  与服务器交互并实现音视频封及网络发送：

后面系列文章对srt 分析：

const URLProtocol ff_libsrt_protocol = {
    .name                = "srt",
    .url_open            = libsrt_open,
    .url_read            = libsrt_read,
    .url_write           = libsrt_write,
    .url_close           = libsrt_close,
    .url_get_file_handle = libsrt_get_file_handle,
    .priv_data_size      = sizeof(SRTContext),
    .flags               = URL_PROTOCOL_FLAG_NETWORK,
    .priv_data_class     = &libsrt_class,
};