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• Merge/Blend/Composite transparent webm files with a jpg/png using ffmpeg

  13 avril 2021, par Lokanath

  I previously had generated color.webm and alpha.webm files withffmpeg using png images.
However, when I play the generated videos in my application it consumes quite some resources so I have decided to create a standard video(No alpha needed), I cannot re-record the videos as there are a lot of them at this point.

  


  I am generating the alpha and color video using the following command ffmpeg -framerate 30 -i img%d.png -filter_complex "alphaextract[a]" -map 0:v -c:v libvpx-vp9 -pix_fmt yuv420p -auto-alt-ref 0 -crf 15 -b:v 0 color.webm -map "[a]" -c:v libvpx-vp9 -pix_fmt yuv420p -auto-alt-ref 0 -crf 15 -b:v 0 alpha.webm

  


  I am looking to get a final video output where in alpha values are replaced with the png/jpg image, it's more like replacing the green screen with a background however in my case greenscreen is the alpha channel.

  


  Could any one let me know how to combine alpha.webm, color.webm with a jpg/png image without minimal or no quality loss ?
.

  


• Playing RTSP in WPF application with low latency using FFMediaElement (FFME)

  17 août 2018, par Paboka

  I’m trying to use FFMediaElement (FFME, WPF MediaElement replacement based on FFmpeg) component to play RSTP live video in my WPF application.

  I have a good connection to my camera and I want to play it with minimum available latency.

  I’ve reduced the latency by changing ProbeSize to its minimal value :

  private void Media_OnMediaInitializing(object Sender, MediaInitializingRoutedEventArgs e)
  
  {
  
    e.Configuration.GlobalOptions.ProbeSize = 32;
  
  }

  But I still have about 1 second of latency since the very beginning of the stream. I mean, when I start playing, I have to wait for 1 second till the video appears and then I have 1s of latency.

  I’ve also tried to change following parameters :

  e.Configuration.GlobalOptions.EnableReducedBuffering = true;
  
  e.Configuration.GlobalOptions.FlagNoBuffer = true;
  
  e.Configuration.GlobalOptions.MaxAnalyzeDuration = TimeSpan.Zero;

  but it gave no result.

  Is there any parameter of FFME or FFmpeg I`ve missed ?

• ffmpeg mp4 to hls vod with extract segment duration without re-encoding

  11 juillet 2021, par Jeremy

  Hello I have h264 mp4 files. What I want to do is convert it to hls without re-encoding. This can be achieve by :

  


  ffmpeg -i input.mp4 -c copy -force_key_frames "expr:gte(t,n_forced*4)" -hls_time 4 -hls_playlist_type vod -hls_segment_type mpegts vid.m3u8


  


  But this problem with this is that it doesn't create extract segment duration :

  


  $ for f in *.ts; do echo -n "$f,"; ffprobe -v error -show_entries format=duration -sexagesimal -of csv=p=0 "$f"; done
vid0.ts,0:00:04.837700
vid1.ts,0:00:05.587200
vid2.ts,0:00:06.006200
vid3.ts,0:00:01.368200
vid4.ts,0:00:02.693867


  


  I don't believe I can't insert keyframes without encoding.

  


  When I run :

  


  ffmpeg -i input.mp4 -codec:v libx264 -force_key_frames "expr:gte(t,n_forced*4)" -hls_time 4 -hls_playlist_type vod -hls_segment_type mpegts vid.m3u8


  


  its works but this is resource intensive as it re-encode the video.

  


  So I am looking for the best way to achieve this while using minimal resource as possible.