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• lavf : Remove codec_tag from dashenc and smoothstreamingenc

  30 juin 2017, par Martin Storsjö

  lavf : Remove codec_tag from dashenc and smoothstreamingenc
  Currently, the tags enforced and set on the segmenter muxer level
  
  mismatch what the mp4/ismv muxer uses (since 713efb2c0d013).
  Skip the codec_tag altogether here, to let the user (try to) set
  
  whichever codec/tag is preferred ; the individual chained muxer will
  
  reject invalid codecs anyway.
  Signed-off-by : Martin Storsjö <martin@martin.st>
  

  • [DBH] libavformat/dashenc.c
  • [DBH] libavformat/smoothstreamingenc.c

• ffmpeg concat drops audio frames

  5 octobre 2017, par Shaun

  I have an mp4 file and I want to take two sequential sections of the video out and render them as individual files, later recombining them back into the original video. For instance, with my video video.mp4, I can run

  ffmpeg -i video.mp4 -ss 56 -t 4 out1.mp4
  
  ffmpeg -i video.mp4 -ss 60 -t 4 out2.mp4

  creating out1.mp4 which contains 00:00:56 to 00:01:00 of video.mp4, and out2.mp4 which contains 00:01:00 to 00:01:04. However, later I want to be able to recombine them again quickly (i.e., without reencoding), so I use the concat demuxer,

  ffmpeg -f concat -safe 0 -i files.txt -c copy concat.mp4

  where files.txt contains

  file out1.mp4
  
  file out2.mp4

  which theoretically should give me back 00:00:56 to 00:01:04 of video.mp4, however there are always dropped audio frames where the concatenation occurs, creating a very unpleasant sound artifact, an audio blip, if you will.

  

  I have tried using async and -af apad on initially creating the two sections of the video but I am still faced with the same problem, and have not found the solution elsewhere. I have experienced this issue in multiple different use cases, so hopefully this simple example will shed some light on the real problem.

• displaying a baseline h264 frames stream in browsers

  6 août 2021, par Thabet Sabha

  So, I have a server that receives a live rtsp stream then generates baseline h264 frames using ffmpeg, which then are sent via an rtcDataChannel to browser, and while the frames arrive as intended, I can't figure out a way to display them on my html5 videoElement,
here is a simplified version of my current approach :

  


  const remoteStream = new MediaSource();&#xA;myVideoElement.src = window.URL.createObjectURL(remoteStream);&#xA;&#xA;// called when remoteStream.readyState === "open"&#xA;let sourceBuffer = remoteStream.addSourceBuffer(&#x27;video/mp4; codecs="avc1.4d002a"&#x27;);&#xA;&#xA;// this gets called when ever a new frame is received from the webrtc data channel.&#xA;function onFrame(frame) {&#xA;      sourceBuffer.appendBuffer(new Uint8Array(frame));&#xA;&#xA;      /*&#xA;      console.log(frame) ==> <buffer 00="00" 01="01" 41="41" 9b="9b" a0="a0" 22="22" 80="80" a5="a5" d7="d7" 42="42" ea="ea" 34="34" 14="14" 85="85" ba="ba" bc="bc" 1b="1b" f2="f2" 71="71" 0d="0d" 8b="8b" e1="e1" 3c="3c" 52="52" d5="d5" 8c="8c" ef="ef" c1="c1" 89="89" 10="10" c5="c5" 05="05" 78="78" ee="ee" 1d="1d" 03="03" 8d="8d" 2896="2896" more="more" bytes="bytes">&#xA;      */&#xA;}&#xA;</buffer>

  


  ffmpeg options :

  


  [
    "-rtsp_transport", "tcp",
    "-i", `${rtspCamURL}`,  
    "-framerate", "15",
    "-c:v", "libx264",
    "-vprofile", "baseline",
    "-b:v", "600k",
    "-bufsize", "600k",
    "-pix_fmt", "yuv420p",
    '-tune', 'zerolatency',
    "-preset", "ultrafast",
    "-f", "rawvideo",
    '-'
]; 


  


  ffmpeg stream is then split using NAL delimiter (to generate individual frames) then each frame is sent via the data channel like so :
Buffer.concat([nalDelimiter, frame]).

  


  I am not sure if i'm missing something as i'm not getting any helpful errors due to the remoteSource closing as soon as the first frame arrives for some reason.

  


  or does the media source just not support raw h264 frames, and if so is there a workaround to solve this issue ? (even if it has to do with changing the ffmpeg params.