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• RTMP live stream directly from NVENC encoder

  16 novembre 2018, par rnd

  I am trying to create a live RTMP stream containing the animation generated with NVIDIA OptiX. The stream is to be received by nginx + rtmp module and broadcasted in MPEG-DASH format. Full chain up to dash.js player is working if the video is first saved to .flv file and then I send it with ffmpeg without any reformatting using command :

  



  ffmpeg -re -i my_video.flv -c:v copy -f flv rtmp://x.x.x.x:1935/dash/test


  



  But I want to stream directly from the code. And with this I am failng... Nginx logs an error "dash : invalid avcc received (2 : No such file or directory)". Then it seems to receive the stream correctly (segments are rolling, dash manifest is there), however the stream is not possible to play in the browser.

  



  I can see only one difference in the manifest between direct stream and stream from file. Codecs attribute of the representation in the direct stream is missed : codecs="avcc1.000000" instead of "avc1.640028" which I get when streaming from file.

  



  My code opens the stream :

  



  av_register_all();
AVOutputFormat* fmt = av_guess_format("flv",
file_name, nullptr);
fmt->video_codec = AV_CODEC_ID_H264;

AVFormatContext* _oc;
avformat_alloc_output_context2(&_oc, fmt, nullptr, "rtmp://x.x.x.x:1935/dash/test");

AVStream* _vs = avformat_new_stream(_oc, nullptr);
_vs->id = 0;
_vs->time_base = AVRational { 1, 25 };
_vs->avg_frame_rate = AVRational{ 25, 1 };

AVCodecParameters *vpar = _vs->codecpar;
vpar->codec_id = fmt->video_codec;
vpar->codec_type = AVMEDIA_TYPE_VIDEO;
vpar->format = AV_PIX_FMT_YUV420P;
vpar->profile = FF_PROFILE_H264_HIGH;
vpar->level = _level;
vpar->width = _width;
vpar->height = _height;
vpar->bit_rate = _avg_bitrate;

avio_open(&_oc->pb, _oc->filename, AVIO_FLAG_WRITE);
avformat_write_header(_oc, nullptr);


  



  Width, height, bitrate, level and profile I get from NVENC encoder settings. I also do the error checking, ommited here. Then I have a loop writing each encoded packets, with IDR frames etc all prepared on the fly with NVENC. The loop body is :

  



  auto & pkt_data = _packets[i];
AVPacket pkt = { 0 };
av_init_packet(&pkt);
pkt.pts = av_rescale_q(_n_frames++, AVRational{ 1, 25 }, _vs->time_base);
pkt.duration = av_rescale_q(1, AVRational{ 1, 25 }, _vs->time_base);
pkt.dts = pkt.pts;
pkt.stream_index = _vs->index;
pkt.data = pkt_data.data();
pkt.size = (int)pkt_data.size();

if (!memcmp(pkt_data.data(), "\x00\x00\x00\x01\x67", 5))
{
    pkt.flags |= AV_PKT_FLAG_KEY;
}

av_write_frame(_oc, &pkt);


  



  Obviously ffmpeg is writing avcc code somewhere... I have no clue where to add this code so the RTMP server can recognize it. Or I am missing something else ?

  



  Any hint greatly appreciated, folks !

  


• RTMP live stream directly from NVENC encoder

  16 novembre 2018, par rnd

  I am trying to create a live RTMP stream containing the animation generated with NVIDIA OptiX. The stream is to be received by nginx + rtmp module and broadcasted in MPEG-DASH format. Full chain up to dash.js player is working if the video is first saved to .flv file and then I send it with ffmpeg without any reformatting using command :

  ffmpeg -re -i my_video.flv -c:v copy -f flv rtmp://x.x.x.x:1935/dash/test

  But I want to stream directly from the code. And with this I am failng... Nginx logs an error "dash : invalid avcc received (2 : No such file or directory)". Then it seems to receive the stream correctly (segments are rolling, dash manifest is there), however the stream is not possible to play in the browser.

  I can see only one difference in the manifest between direct stream and stream from file. Codecs attribute of the representation in the direct stream is missed : codecs="avcc1.000000" instead of "avc1.640028" which I get when streaming from file.

  My code opens the stream :

  av_register_all();
  
  AVOutputFormat* fmt = av_guess_format("flv",
  
  file_name, nullptr);
  
  fmt->video_codec = AV_CODEC_ID_H264;
  
  
  
  AVFormatContext* _oc;
  
  avformat_alloc_output_context2(&_oc, fmt, nullptr, "rtmp://x.x.x.x:1935/dash/test");
  
  
  
  AVStream* _vs = avformat_new_stream(_oc, nullptr);
  
  _vs->id = 0;
  
  _vs->time_base = AVRational { 1, 25 };
  
  _vs->avg_frame_rate = AVRational{ 25, 1 };
  
  
  
  AVCodecParameters *vpar = _vs->codecpar;
  
  vpar->codec_id = fmt->video_codec;
  
  vpar->codec_type = AVMEDIA_TYPE_VIDEO;
  
  vpar->format = AV_PIX_FMT_YUV420P;
  
  vpar->profile = FF_PROFILE_H264_HIGH;
  
  vpar->level = _level;
  
  vpar->width = _width;
  
  vpar->height = _height;
  
  vpar->bit_rate = _avg_bitrate;
  
  
  
  avio_open(&_oc->pb, _oc->filename, AVIO_FLAG_WRITE);
  
  avformat_write_header(_oc, nullptr);

  Width, height, bitrate, level and profile I get from NVENC encoder settings. I also do the error checking, ommited here. Then I have a loop writing each encoded packets, with IDR frames etc all prepared on the fly with NVENC. The loop body is :

  auto & pkt_data = _packets[i];
  
  AVPacket pkt = { 0 };
  
  av_init_packet(&pkt);
  
  pkt.pts = av_rescale_q(_n_frames++, AVRational{ 1, 25 }, _vs->time_base);
  
  pkt.duration = av_rescale_q(1, AVRational{ 1, 25 }, _vs->time_base);
  
  pkt.dts = pkt.pts;
  
  pkt.stream_index = _vs->index;
  
  pkt.data = pkt_data.data();
  
  pkt.size = (int)pkt_data.size();
  
  
  
  if (!memcmp(pkt_data.data(), "\x00\x00\x00\x01\x67", 5))
  
  {
  
      pkt.flags |= AV_PKT_FLAG_KEY;
  
  }
  
  
  
  av_write_frame(_oc, &pkt);

  Obviously ffmpeg is writing avcc code somewhere... I have no clue where to add this code so the RTMP server can recognize it. Or I am missing something else ?

  Any hint greatly appreciated, folks !

• How to manually reset the offset of an mp4 video created from m4s files ?

  12 août 2020, par natdev

  I'm building a service that combine .m4s files (from a dash stream) to a mp4 video.
  
I have some sample m4s files from a random point in time of a stream,
  
using ffmpeg on those file + the init file does the job.

  


  cat init.mp4 032.m4s 033.m4s 034.m4s > output.mp4


  


  I have tried concating the m4s files to the mp4 init file and I manage to play the video,
  
but there is an offset from the encoded video segments.

  


  I guess ffmpeg does reset that somehow, and I was wondering how can I reset that offset as well ?
  
Having a little bit of experience with dash, I know that there is a field name presentationTimeOffset that is responsible to set the offset.