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• Audio/Video de-synchronisation when playing a video on Chrome

  30 novembre 2020, par Sonia Seddiki

  I've been recently working on a project where I try to play a "custom-made" video on an HTML5 player. By custom-made, I mean I concatenate a bunch of videos together using FFmpeg concat demuxer, each of them having the same properties (FPS, bitrate, resolution, timebase, etc).

  


  Now, I'm having a few issues regarding audio/video synchronisation, with a twist : it does not happen on every video player. The video is perfectly synchronised when read on Firefox, but not on Chrome. It is synchronised when read on a "local" video player like VLC.

  


  I assume it has to do with how the video data is presented to the player. I read a little about PTS, DTS, I-P-B frames and I guess the final output may be a little messed up ? But I don't really have a strong lead to follow here.

  


  I tried to find info on how the HTML5 player was implemented by both browsers, but couldn't find much (again, I'm probably not googling this right). Does anyone here know a bit more about the technical aspect of how a video is actually played in a browser ? Or any clue as to why this de-synchronisation doesn't happen on every platform ?

  


  Thank you so much for your help !

  


• When using MoviePy to resize a video how do I know what bitrate to use to maintain quality when writing the new video to disk

  4 juillet 2016, par Michael

  Expanding on this question How To Resize a Video Clip Python about using MoviePy to resize a video.

  When it comes time to write the resized video to disk
  How do I select a bitrate value so there is as little loss of quality as possible ?

  The original video is 4.8M on disk and is .mp4

  Bit rate set when writing to disk

      clip_resized.write_videofile(ResizedClip,bitrate="5000k")

  Gives a file of 8.3MB in size

  No bit rate set

      clip_resized.write_videofile(ResizedClip)

  Gives a file of 3.3MB

• FFMPEG Flutter - Generating video from images not playing on default android video players

  17 février 2023, par Abdullah Riaz

  I'm trying to generate a video from multiple image files in FFMPEG Flutter. I'm using https-gpl package.

  


  ffmpeg_kit_flutter_https_gpl: 5.1.0


  


  I'm using this command.

  


   "-f concat -safe 0 -protocol_whitelist file,http,https,tcp,tls,crypto -i $filePath -stream_loop -1 -i $musicFile -vf 'scale=3840:2880:force_original_aspect_ratio=decrease,pad=3840:2880:(ow-iw)/2:(oh-ih)/2,setsar=1' -r 6 -c:v libx264 -crf 40 -profile:v main -preset veryfast -pix_fmt yuv420p -t $totalTime $outputFilePath"


  


  Where you can clearly see, I'm encoding video in libx264 with yuv420p.

  


  The thing is, the video is created successfully and played smoothly on the VLC. But it doesn't show anything on normal/default android video players although it plays the audio.

  


  I've tried multiple things but all failed to run video on default android video players. I've even tried multiple android phones.
What am I doing wrong here ?