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• Error when transcode webm to mp4 using ffmpeg.wasm

  17 février 2021, par arpo

  I have this webm file recorded using MediaRecorder in Chrome.
https://cdn.hibervr.com/video/loop3.webm

  


  When I try to transcode it using ffmpeg.wasm, https://github.com/ffmpegwasm/ffmpeg.wasm

  


  Using this codepen, taken from the official site :
https://codepen.io/jeromewu/pen/NWWaMeY

  


  I get this error in the console and the file isn't playable.

  


  net::ERR_REQUEST_RANGE_NOT_SATISFIABLE


  


  Any clues about how to fix it ?

  


  It works using other webm files like this.
https://phoboslab.org/files/ffmpeg-mt-fixed/jumparound.webm

  


• Header missing in mpg, in spite of using avformat_write_header

  23 novembre 2012, par TheSHEEEP

  I am encoding a live rendered video to mpg and/or mp4 (depends on the later usage of the video) using the ffmpeg C API. When encoding to mp4, everything is well. But when encoding to mpg, the resulting video cannot be played by any player. A quick call to ffprobe on it reveals that the header is missing. But this seems pretty much impossible, as I am explicitly writing it.

  This is how I write the header, before any frame is encoded :

  // ptr->oc is the AVFormatContext
  
  int error = avformat_write_header(ptr->oc, NULL);
  
  if (error < 0)
  
  {
  
      s_logFile << "Could not write header. Error: " << error << endl;
  
      fprintf(stderr, "Could not write header. Error: '%i'\n", error);
  
      return 1;
  
  }

  There never is any error when writing the header.

  For encoding, I am following the official muxing.c example, so I do set the CODEC_FLAG_GLOBAL_HEADER flag. I use CODEC_ID_MPEG2VIDEO (for video) and CODEC_ID_MP2 (for audio).

  The result mpg does work when I "encode" it in an additional step with an external ffmpeg executable like this : "ffmpeg -i ownEncoded.mpg -sameq -y working.mpg".
  So it seems all the data is there, only the header is missing for some reason...

  Here is the only thing ffmpeg is reporting before/when writing the header :

  mpeg -------------------
  
  lvl: 24
  
  msg: VBV buffer size not set, muxing may fail

  Could that be the problem ?

  I wonder what could be wrong here as I encode mp4 with the exact same function, except setting some special values like qmin, qmax, me_method, etc. when encoding to mp4. Do I probably have to set any special values so that ffmpeg really does write the header correctly ?

• utvideoenc : Enable support for multiple slices and use them

  14 février 2014, par Jan Ekström

  utvideoenc : Enable support for multiple slices and use them
  The official Ut Video decoder only threads with slices, thus until
  
  now any files encoded by the libavcodec encoder have only been
  
  decodable with a single thread. The default slice count is now
  
  set to subsampled_height / 120.
  Also sets slices to 1 for the Ut Video encoder tests to keep them
  
  green.
  Signed-off-by : Michael Niedermayer <michaelni@gmx.at>
  

  • [DH] libavcodec/utvideoenc.c
  • [DH] tests/fate/utvideo.mak