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• ffmpeg limit the size of transcoded output as 104857600 bytes

  22 juin 2017, par shamaleyte

  I am converting the video.webm into .wav file with the following options.
  However the output file is just pretty huge !

  I need to reduce the size of it, actually it would be really cool to limit the output size as 104857600 bytes and let the ffmpeg library handle the rest (like automatically adjust the quality)
  Any idea how to do that ?

  If that is not possible, how can I lower the quality like 50% ?

  return new Promise(function (resolve, reject) { 
  
      var proc = new ffmpeg({
  
          source: file,
  
          nolog: false
  
      });
  
  
  
  
  
  
  
     proc.addOptions([
  
          '-f ' + format,
  
          '-ar 16000',
  
          '-vn'
  
      ]);
  
  
  
      proc.on('error', function (err, stdout, stderr) {
  
          reject(err)          
  
      });
  
      proc.save(file.split(".")[0] + "." + format).on('end', function () {            
  
          resolve(file.split(".")[0] + "." + format);
  
      })
  
  });

• vdpau : do not use buggy HEVC support by default

  1er juillet 2017, par wm4

  vdpau : do not use buggy HEVC support by default
  NVIDIA broke its own API when using VDPAU decoding. If you retrieve the
  
  decoded YUV data, or if you map the surfaces with GL interop, the result
  
  are interlacing artifacts. The only way to get non-broken data is by
  
  using the vdpau video mixer to convert it to RGB. There is no way to
  
  block the non-working operations in a reasonable way (a VdpVideoSurface
  
  has to support all operations).
  NVIDIA refuses to fix this issue (they "fixed" it by making it work with
  
  the video mixer, but the rest is still broken). There is no sign of that
  
  changing.
  Do not use HEVC by default with the generic hwaccle API. Detect whether
  
  it's the NVIDIA native implementation, and exit with an error. (The same
  
  thing work with the MESA implementation.)
  As an escape hatch and to allow applications to use the decoder if they
  
  really want to (perhaps because they make sure to explicitly use the
  
  video mixer), reuse AV_HWACCEL_FLAG_ALLOW_PROFILE_MISMATCH to disable
  
  this check.
  Once NVIDIA fixes the bug, working driver versions could be detected,
  
  and it could be allowed again.
  

  • [DH] libavcodec/vdpau.c

• FFmpeg C Api opening and reading raw PCM audio file

  11 juillet 2017, par Adam

  My program needs to read raw PCM signed 16bit little endian audio file, which does not have a header.

  Currently I’m using avformat_open_input function to open the file. This function not only initializes structures, but also read the header of the file, so later when I read packages using av_read_frame, I don’t get packages from beginning of the file, which I guess was already read as a header. That way I lose 23 miliseconds of audio at the beginning, rest of the file is ok.

  How should I initialize AVFormatContext Struct to correctly read raw audio PCM input file ?

  Edit :

  I know that there is this note :

  If you want to use custom IO, preallocate the format context and set its pb field.

  But I don’t know if this is the correct way to solve my problem ? If so, what should I initialize myself ?