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• FFMpeg is writing a matplotlib animation with diminishing quality

  3 mars 2017, par Bryan Stafford

  I am trying to create a bunch of animations that follow the paths National Hockey League teams travel during the current season. Currently, my animation looks like this.

  As you can see, the animation begins decently sharp but within 2 seconds the quality bottoms out and everything is grainy.

  The relevant code is this :

  ani = animation.FuncAnimation(fig, update, frames=len(all_x + 20), 
  
                                interval=75, repeat=False)
  
  filepath =  map_team + '.mp4'
  
  ani.save(filepath, writer='ffmpeg', fps=30)
  
  plt.tight_layout()
  
  plt.show()

  I have chosen FFMpeg as my writer because I hope to put about 30 graphics online and the MP4 format keeps each file around 1.5MB. If there’s a way to keep the graphics sharp, with low file sizes, and able to be uploaded onto Imgur, I would love to do that with my project.

  Thanks.

• HEVC File bigger after converting from h264

  26 janvier 2019, par Aaroknight

  I’m currently working an an automated Python script for indexing and converting all my movies and episodes with ffmpeg. I use subprocess.call() for running the ffmpeg command and tested this command with some movies. As expected the big h264 files were converted to merely one third of what they used to have.

  But now that I was testing the method I found that a converted episode (about 400MB in h264) had over 1,6GB in hevc. I have absolutely no idea why the new file would be that much bigger in hevc.
  This is my code :

  def convert(path):
  
      outvid = path.strip(".mkv") + "h265.mkv"
  
  
  
      cmd = ["ffmpeg", "-i", path, "-map", "0", "-map_metadata", "0", "-map_chapters", "0", "-c:v", "libx265",
  
             "-c:a", "copy", "-c:s", "copy", "-preset", "ultrafast", "-x265-params", "lossless=1", outvid]
  
      subprocess.call(cmd)
  
  
  
  convert("/Volumes/2TB/Black Butler/Season 1/Black Butler S01E01.mkv")

  I don’t have that much experience with ffmpeg, nor with subprocess. This is one of my first bigger projects. I hope someone can tell me what the problem might be.

  UPDATE
  Problem applies only for small video files. I now just check for the file size and skip the small files. Wouldn’t have made much of a difference anyway.

  

• Impossible to redirect video stream after conversion (mkv to mp4)

  17 décembre 2019, par elgrusko

  I’m currently realising a school project which aims a streaming video website (like Netflix) using torrent-stream (with the magnet link). I am using NodeJS for the stream part.

  My problem is : I can’t redirect the stream to the HTML 5 player while i’m trying to stream and converting (with ffmpeg) video at the same time. I think it’s because I just can’t know what’s will be the final size of the converted file.
  In browser’s console I have this message : net::ERR_CONTENT_LENGTH_MISMATCH 200 (OK)

  I tried to put this in the header : Transfer-Encoding: chunked instead of Content-Length
  I specify that the stream (before conversion) works perfectly

  This is my code :

  getTorrentFile.then(function (file) {
  
                  res.setHeader('Content-Type', 'video/mp4');
  
                  res.setHeader('Content-Length', file.length);
  
                  const ranges = parseRange(file.length, '15' /* variable à comprendre */, { combine: true });
  
                  console.log(ranges);
  
                  if (ranges === -1) {
  
                      // 416 Requested Range Not Satisfiable
  
                      console.log('416')
  
                      res.statusCode = 416;
  
                      return res.end();
  
                  } else if (ranges === -2 || ranges.type !== 'bytes' || ranges.length > 1) {
  
                      // 200 OK requested range malformed or multiple ranges requested, stream ent'ire video
  
                      if (req.method !== 'GET') return res.end();
  
                      console.log('200')
  
                      stream = file.createReadStream()
  
                      ffmpeg(stream)
  
                      .videoCodec('libx264')
  
                      .audioCodec('aac')
  
                      .output(res)
  
                      .output('./video/' + film + '_s' + season + '_e' + episode + '.mp4')
  
                      .outputFormat('mp4')
  
                      .outputOptions('-movflags frag_keyframe+empty_moov')
  
                      .on('error', function(err) {
  
                          console.log('An error occurred: ' + err.message);
  
                      })
  
                      .on('progress', function(progress) {
  
                          console.log('Processing: ' + progress.targetSize + 'kb done');
  
                        })
  
                      .on('end', function() {
  
                          console.log('Processing finished !');
  
                      })
  
                      .addOutputOption('-acodec')
  
                      .run()

  Sorry if i’m not really clear, ask me some questions if you need more informations :)

  Thanks for your help, bye :)