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• ffmpeg how to save decoded audio data to pcm

  21 avril 2015, par Jason

  I have succeed decode audio data from a mp4 using avcodec_decode_audio4， I want to save the decoded frames,so I tried below

  if (got_frame) {
  
    int size;
  
    uint8_t *data;
  
    int ref = 0;
  
    ret = swr_convert(swr, &data, frame->nb_samples, (const uint8_t **)frame->extended_data, frame->nb_samples);
  
    //fwrite(data, 1, frame->nb_samples, fp_audio);
  
    ref++;
  
    int szie = av_samples_get_buffer_size(NULL, 2, 1024, AV_SAMPLE_FMT_FLTP, 1);
  
  
  
    for (int i = 0; i < frame->linesize[0]/4; i++)
  
    {
  
      fwrite(frame->data[0] + 4*i, 1, 4, fp_audio);
  
      fwrite(frame->data[1] + 4*i, 1, 4, fp_audio);
  
      ref++;
  
    }
  
  
  
  
  
  
  
    av_frame_unref(frame);
  
  }

  but the pcm sounds strange, I also tried directed write as follows

  fwrite(frame->data[0], 1, frame->linesize[0], fp_audio);

  or :

  fwrite(frame->data[0], 1, frame->linesize[0], fp_audio);
  
  fwrite(frame->data[1], 1, frame->linesize[0], fp_audio);

  I know that the decoded pcm is AV_SAMPLE_FMT_FLTP
  any help would be appreciated

• sauce : test filetype correctly for datatype 5 (binary text)

  14 décembre 2012, par Peter Ross

  sauce : test filetype correctly for datatype 5 (binary text)

• Creating a convertAll() function that converts all .filetype in working directory

  5 janvier 2019, par Risviltsov

  I seem to not know proper bash syntax ; despite this, I’ve tried to create a tool that changes the dimensions of all files of a ffmpeg-accepted filetype in the working directory and converts it to another ffmpeg-accepted filetype. In this instance, this tool converts all .webm files over 1080x720 into 1080x-1 or -1x720 .mp4 files. If the .webm file is under 1080x720, the new .mp4 file will have the same dimensions.

  However, there’s a wrench in the tool.

  convertAll () {
  
  local wantedWidth = 1080
  
  local wantedHeight = 720
  
  for i in *.webm; do
  
  local newWidth = $i.width
  
  local newHeight = $i.height
  
  until [$newWidth <= $wantedWidth && $newHeight <= $wantedHeight]; do
  
  if [$videoWidth > $wantedWidth]; then
  
  newHeight = $newWidth*($wantedWidth/$newWidth)
  
  newWidth = $newWidth*($wantedWidth/$newWidth)
  
  fi
  
  if [$videoHeight > $wantedHeight]; then
  
  newWidth = $newWidth*($wantedHeight/$newHeight)
  
  newHeight = $newHeight*($wantedHeight/$newHeight)
  
  fi
  
  done
  
  ffmpeg -i "$i" -vf scale=$newWidth:$newHeight "${i%.*}.mp4";
  
  done
  
  echo "All files have been converted."
  
  }

  What this returns is a bunch of lines that look like this :

  bash: [: missing ']'
  
  bash: [: missing ']'
  
  bash: =: No such file or directory

  My best guess is that BASH can’t do mathematics, and that I’m declaring and editing my variables incorrectly.

  I’d like some input on this --- my lack of experience is really getting me here.