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• FFMPEG RTSP stream to MPEG4/H264 file using libx264

  16 octobre 2020, par Phi

  Heyo folks,

  



  I'm attempting to transcode/remux an RTSP stream in H264 format into a MPEG4 container, containing just the H264 video stream. Basically, webcam output into a MP4 container.

  



  I can get a poorly coded MP4 produced, using this code :

  



  // Variables here for demo
AVFormatContext * video_file_output_format = nullptr;
AVFormatContext * rtsp_format_context = nullptr;
AVCodecContext * video_file_codec_context = nullptr;
AVCodecContext * rtsp_vidstream_codec_context = nullptr;
AVPacket packet = {0};
AVStream * video_file_stream = nullptr;
AVCodec * rtsp_decoder_codec = nullptr;
int errorNum = 0, video_stream_index = 0;
std::string outputMP4file = "D:\\somemp4file.mp4";

// begin
AVDictionary * opts = nullptr;
av_dict_set(&opts, "rtsp_transport", "tcp", 0);

if ((errorNum = avformat_open_input(&rtsp_format_context, uriANSI.c_str(), NULL, &opts)) < 0) {
    errOut << "Connection failed: avformat_open_input failed with error " << errorNum << ":\r\n" << ErrorRead(errorNum);
    TacticalAbort();
    return;
}

rtsp_format_context->max_analyze_duration = 50000;
if ((errorNum = avformat_find_stream_info(rtsp_format_context, NULL)) < 0) {
    errOut << "Connection failed: avformat_find_stream_info failed with error " << errorNum << ":\r\n" << ErrorRead(errorNum);
    TacticalAbort();
    return;
}

video_stream_index = errorNum = av_find_best_stream(rtsp_format_context, AVMEDIA_TYPE_VIDEO, -1, -1, NULL, 0);

if (video_stream_index < 0) {
    errOut << "Connection in unexpected state; made a connection, but there was no video stream.\r\n"
        "Attempts to find a video stream resulted in error " << errorNum << ": " << ErrorRead(errorNum);
    TacticalAbort();
    return;
}

rtsp_vidstream_codec_context = rtsp_format_context->streams[video_stream_index]->codec;

av_init_packet(&packet);

if (!(video_file_output_format = av_guess_format(NULL, outputMP4file.c_str(),  NULL))) {
    TacticalAbort();
    throw std::exception("av_guess_format");
}

if (!(rtsp_decoder_codec = avcodec_find_decoder(rtsp_vidstream_codec_context->codec_id))) {
    errOut << "Connection failed: connected, but avcodec_find_decoder returned null.\r\n"
        "Couldn't find codec with an AV_CODEC_ID value of " << rtsp_vidstream_codec_context->codec_id << ".";
    TacticalAbort();
    return;
}

video_file_format_context = avformat_alloc_context();
video_file_format_context->oformat = video_file_output_format;

if (strcpy_s(video_file_format_context->filename, sizeof(video_file_format_context->filename), outputMP4file.c_str())) {
    errOut << "Couldn't open video file: strcpy_s failed with error " << errno << ".";
    std::string log = errOut.str();
    TacticalAbort();
    throw std::exception("strcpy_s");
}

if (!(video_file_encoder_codec = avcodec_find_encoder(video_file_output_format->video_codec))) {
    TacticalAbort();
    throw std::exception("avcodec_find_encoder");
}

// MARKER ONE

if (!outputMP4file.empty() &&
    !(video_file_output_format->flags & AVFMT_NOFILE) &&
    (errorNum = avio_open2(&video_file_format_context->pb, outputMP4file.c_str(), AVIO_FLAG_WRITE, nullptr, &opts)) < 0) {
    errOut << "Couldn't open video file \"" << outputMP4file << "\" for writing : avio_open2 failed with error " << errorNum << ": " << ErrorRead(errorNum);
    TacticalAbort();
    return;
}

// Create stream in MP4 file
if (!(video_file_stream = avformat_new_stream(video_file_format_context, video_file_encoder_codec))) {
    TacticalAbort();
    return;
}

AVCodecContext * video_file_codec_context = video_file_stream->codec;

// MARKER TWO

// error -22/-21 in avio_open2 if this is skipped
if ((errorNum = avcodec_copy_context(video_file_codec_context, rtsp_vidstream_codec_context)) != 0) {
    TacticalAbort();
    throw std::exception("avcodec_copy_context");
}

//video_file_codec_context->codec_tag = 0;

/*
// MARKER 3 - is this not needed? Examples suggest not.
if ((errorNum = avcodec_open2(video_file_codec_context, video_file_encoder_codec, &opts)) < 0)
{
    errOut << "Couldn't open video file codec context: avcodec_open2 failed with error " << errorNum << ": " << ErrorRead(errorNum);
    std::string log = errOut.str();
    TacticalAbort();
    throw std::exception("avcodec_open2, video file");
}*/

//video_file_format_context->flags |= AVFMT_FLAG_GENPTS;
if (video_file_format_context->oformat->flags & AVFMT_GLOBALHEADER)
{
    video_file_codec_context->flags |= CODEC_FLAG_GLOBAL_HEADER;
}

if ((errorNum = avformat_write_header(video_file_format_context, &opts)) < 0) {
    errOut << "Couldn't open video file: avformat_write_header failed with error " << errorNum << ":\r\n" << ErrorRead(errorNum);
    std::string log = errOut.str();
    TacticalAbort();
    return;
}


  



  However, there are several issues :

  



  

  1. I can't pass any x264 options to the output file. The output H264 matches the input H264's profile/level - switching cameras to a different model switches H264 level.

  


  2. The timing of the output file is off, noticeably.

  


  3. The duration of the output file is off, massively. A few seconds of footage becomes hours, although playtime doesn't match. (FWIW, I'm using VLC to play them.)

  


  



  Passing x264 options

  



  If I manually increment PTS per packet, and set DTS equal to PTS, it plays too fast, 2-3 seconds' worth of footage in one second playtime, and duration is hours long. The footage also blurs past several seconds, about 10 seconds' footage in a second.

  



  If I let FFMPEG decide (with or without GENPTS flag), the file has a variable frame rate (probably as expected), but it plays the whole file in an instant and has a long duration too (over forty hours for a few seconds). The duration isn't "real", as the file plays in an instant.

  



  At Marker One, I try to set the profile by passing options to avio_open2. The options are simply ignored by libx264. I've tried :

  



  av_dict_set(&opts, "vprofile", "main", 0);
av_dict_set(&opts, "profile", "main", 0); // error, missing '('
// FF_PROFILE_H264_MAIN equals 77, so I also tried
av_dict_set(&opts, "vprofile", "77", 0); 
av_dict_set(&opts, "profile", "77", 0);


  



  It does seem to read the profile setting, but it doesn't use them. At Marker Two, I tried to set it after the avio_open2, before avformat_write_header .

  



  // I tried all 4 av_dict_set from earlier, passing it to avformat_write_header.
// None had any effect, they weren't consumed.
av_opt_set(video_file_codec_context, "profile", "77", 0);
av_opt_set(video_file_codec_context, "profile", "main", 0);
video_file_codec_context->profile = FF_PROFILE_H264_MAIN;
av_opt_set(video_file_codec_context->priv_data, "profile", "77", 0);
av_opt_set(video_file_codec_context->priv_data, "profile", "main", 0);


  



  Messing with privdata made the program unstable, but I was trying anything at that point.
I'd like to solve issue 1 with passing settings, since I imagine it'd bottleneck any attempt to solve issues 2 or 3.

  



  I've been fiddling with this for the better part of a month now. I've been through dozens of documentation, Q&As, examples. It doesn't help that quite a few are outdated.

  



  Any help would be appreciated.

  



  Cheers

  


• Merge commit '4795e4f61f993940c5384044caff56cc15078698'

  19 mai 2017, par Clément Bœsch

  Merge commit '4795e4f61f993940c5384044caff56cc15078698'
  * commit '4795e4f61f993940c5384044caff56cc15078698' :
  
    alac : Convert to the new bitstream reader
  
    rtp : Convert to the new bitstream reader
  
    mov : Convert to the new bitstream reader
  This merge is a noop, see
  
  http://ffmpeg.org/pipermail/ffmpeg-devel/2017-April/209609.html
  Merged-by : Clément Bœsch <u@pkh.me>
  

• Merge commit '54dcd2288546e135986338107ea87db1fcedd633'

  19 mai 2017, par Clément Bœsch

  Merge commit '54dcd2288546e135986338107ea87db1fcedd633'
  * commit '54dcd2288546e135986338107ea87db1fcedd633' :
  
    als : Convert to the new bitstream reader
  This commit is a noop, see
  
  http://ffmpeg.org/pipermail/ffmpeg-devel/2017-April/209609.html
  Merged-by : Clément Bœsch <u@pkh.me>