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• Why doesn't FFmpeg work when using yt-dlp in python script ?

  11 mai 2022, par spelle

  I'm trying to download a video using yt-dlp in python.

  


  ydl_opts = {'format': 'bv+ba/b'}
with YoutubeDL(ydl_opts) as ydl:
     ydl.download('https://www.reddit.com/r/cats/comments/re37dn/weve_been_feeding_this_stray_for_several_years/')


  


  But I'm reaching an FFmpeg error in the log

  


  [generic] 1o8t9ollwx481: Requesting header
[redirect] Following redirect to https://www.reddit.com/r/cats/comments/re37dn/weve_been_feeding_this_stray_for_several_years/
[Reddit] re37dn: Downloading JSON metadata
[Reddit] re37dn: Downloading m3u8 information
[Reddit] re37dn: Downloading MPD manifest
[info] 1o8t9ollwx481: Downloading 1 format(s): dash-video_4419291+dash-audio_0_133951
WARNING: You have requested merging of multiple formats but ffmpeg is not installed. The formats won't be merged.
[download] Destination: We’ve been feeding this stray for several years, but she’s lost a lot of weight and I don’t think she would last outside for another winter, so I brought her in. [1o8t9ollwx481].fdash-video_4419291.mp4
[download] 100% of 5.18MiB in 00:00               
[download] Destination: We’ve been feeding this stray for several years, but she’s lost a lot of weight and I don’t think she would last outside for another winter, so I brought her in. [1o8t9ollwx481].fdash-audio_0_133951.m4a
[download] 100% of 161.32KiB in 00:00


  


  FFmpeg is installed through pip and added in PATH.

  


• How to append fMP4 chunks to SourceBuffer ?

  24 octobre 2020, par Stefan Falk

  I have finally managed to create an fMP4 but now I am not able to seek or play the file depending on what I do in the file.

  


  On my backend I am taking the file and convert it to MP4 or fragmented MP4.

  


  The file gets send to the clients chunk-wise but this approach does not seem to work as it used to work on Chrome (bot not on Firefox) when using MP3.

  


  How I played MP3

  


  Say we have a 10 seconds track that is 1 MB in size which I want to start playing from second five. I want to load chunks of 1 second.

  


  Thus, I have offset = 5 / 10 * file_size and chunkSize = 1 / 10 * file_size`.

  


  With this I just started loading the MP3-file at an offset of 0.5 MB and loaded the chunks as needed where each chunk was 0.1 MB in size.

  


  This worked because before actually playing the file, I loaded the first bytes of the file and appended it to the SourceBuffer as well s.t. it was able to load the meta-information of the file. However, this approach is just not working for fMP4.

  


  What I tried with fMP4

  


  So, I have been converting MP3 to fMP4 with the MP3-approach ..

  


  .. using +dash (can play but not seek)

  


  ffmpeg -i input.mp3 -acodec aac -b:a 256k -f mp4 -movflags +dash output.mp4


  


  .. using frag_keyframe+empty_moov (cannot play on Chrome)

  


  ffmpeg -i input.mp3 -acodec aac -b:a 256k -f mp4 -movflags frag_keyframe+empty_moov output.mp4


  


  On the client the chunks get appended to a SourceBuffer (as explained above) after creating it with the Mime-Type audio/mp4; codecs="mp4a.40.2" :

  


  this.sourceBuffer = this.mediaSource
                        .addSourceBuffer('audio/mp4; codecs="mp4a.40.2"');


  


  and

  


  private appendSegment = (chunk) => {
  try {
    this.sourceBuffer.appendBuffer(chunk);
  } catch {
    return;
  }
}


  


  The problem is that I can only play the +dash converted file if I start reading it from the start and continue adding chunks.

  


  However, if I start reading the file from further down, the audio gets never played.

  


  playTrack(track, 0.0);  // Start at second 0 works
playTrack(track, 10.0); // Start at second 10 does not work


  


• Convert GIF to MP4 with ffmpeg with palette color

  28 mars 2019, par NAG

  Palettegen is ok :

  ffmpeg()
  
  .input('temp/' + input.hash)
  
  .outputOptions(["-vf fps=15,scale=320:-1:flags=lanczos,palettegen"])
  
  .output('temp/palette.png')

  the conversion using the palette return a error :

  Error : Cannot find a matching stream for unlabeled input pad 1 on filter Parsed_paletteuse_0

  ffmpeg()
  
  .input('color=' + input.bg)
  
  .inputFormat('lavfi')
  
  .input('temp/' + input.hash)
  
  .inputFormat('gif')
  
  .input('temp/palette.png')
  
  .outputOptions('-lavfi paletteuse')
  
  .complexFilter(["[0][1]scale2ref[bg][gif]", "[bg]setsar=1[bg]", "[bg][gif]overlay=shortest=1[o]", "[o]scale=trunc(iw/2)*2:trunc(ih/2)*2"])
  
  .outputOptions(['-pix_fmt yuv420p', '-movflags frag_keyframe+empty_moov', '-movflags +faststart', '-crf 5'])
  
  .toFormat('mp4')
  
  .output('temp/final-' + input.hash)

  ffmpeg final command :

  ffmpeg -f lavfi -i color=ffffff -f gif -i temp/cf81f99083462f693406e8fd03ca7009 -i temp/palette.png -y -filter_complex [0][1]scale2ref[bg][gif];[bg]setsar=1[bg];[bg][gif]overlay=shortest=1[o];[o]scale=trunc(iw/2)*2:trunc(ih/2)*2 -lavfi paletteuse -pix_fmt yuv420p -movflags frag_keyframe+empty_moov -movflags +faststart -crf 5 -f mp4 temp/final-cf81f99083462f693406e8fd03ca7009