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• Output resolution substantially below input resolution [closed]

  29 août 2024, par bobford

  I have written an Android app to overlay a watermark png using FFMpeg 6.0 which works fine on 1k and 4k videos. In both cases the output resolution substantially deteriorates albeit consistent with the reduction in file size. In both cases, the original width-height pixel sizes are retained.

  


  The ffmpeg command is :

  


  String[] array = new String[] {"-i ", inputFile, " -i ", watermarkFile, " -filter_complex ", overlayPosition, " -codec:a copy ", outputFile};
String delimiter = "";
String command = String.join(delimiter, array);


  


  I would like to retain the original resolution, or as close as possible, even with the larger file size.
It would seem there are default parameters which I am unaware of, and have absolutely no idea of how to find them, even after extensive searching. Thank you for your help !

  


• How to cut video frame specific with ffmpeg and convert framerate ?

  1er mars 2018, par Alexander Pospischil

  since a couple of days i encounter a problem with ffmpeg which is actually driving me mad...
  I try to use FFMPEG’s filter_complex in order to extract certain short segments of a videofile (shot at 60fps). I know the exact frames from the original footage which i want to use for cutting. I use the trim filter command together with setpts, if i want to change the speed of each snippet.
  In the actual case i want to have the first snippet in original speed (1.0), and the resulting output video should be at 30fps instead of the original footages 60fps.
  Here’s the code i’m using :

  ffmpeg -y -i footage60fps -filter_complex " 
  
  [0:v]trim=start_frame=28:end_frame=82,setpts=PTS-
  
  STARTPTS,setpts=1.0*PTS[v0]; 
  
  [0:v]trim=start_frame=10:end_frame=20,setpts=PTS-
  
  STARTPTS,setpts=2.0*PTS[v1]; [v0][v1]concat=n=2:v=1:a=0[out] " -map [out] -
  
  preset ultrafast -r 30 output30fps.mp4

  The result i’m expecting would be, that in the first snippet (frame 28 until last before 82) ffmpeg would drop every second frame ([x]) in order to have it converted from 60fps to 30fps at normal speed :
  [28][x][30][x][32][x]...[80]

  However, the result i get is :
  [28][29][30][31][x][33][x][35][x]...[81]

  Does anybody understand this behavior ? How could i solve it ? It seems like a minor issue, but it turns out to be so annoying when cutting sharp on music etc... Any help would be highly appreciated !

• How can I amplify volume with Audacity and ffmpeg ?

  18 octobre 2019, par Christos Hayward

  I have an MP4 recording where the video is present, but much too quiet. What I’ve done before is :

  ffmpeg -i master.mp4 -i amplified.wav -vcodec copy output.mp4

  I’ve tried various permutations, and the output ffmpeg builds is, as viewed by my browser, at the original overly quiet volume. If I load the Audacity-generated .wav, it plays as loudly as intended. (N.B. I have enabled clipping in Audacity, and I have not noticed it to fail at the amplifications I’ve tried with it.) However, the final result seems to retain unaltered the original audio track along in the video.

  How, with present software or other software, can I assign amplified.wav to be the new audio track to master.mp4 in output.mp4 ?