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• Android FFmpeg cant set quality of image

  24 octobre 2017, par TheOtherguyz4kj

  I am working with FFmpeg on Android, I am trying to extract frames from a video every second. I made this command that works well :

  final String cmd[] = {
  
  
  
              "-i",
  
              videoPath,
  
              "-vf",
  
              "fps=1",
  
              mediaStorageDir.getAbsolutePath() +
  
              "out%d.png"
  
      };

  Now I want to reduce the quality of the extracted frames so I tried this but get the error :

  final String cmd[] = {
  
  
  
              "-i",
  
              videoPath,
  
              "-vf",
  
              "fps=1",
  
              "-qscale:v 12",
  
              mediaStorageDir.getAbsolutePath() +
  
              "out%d.png"
  
      };

  At least one output file must be specified

  What is the problem ? I have searched online a lot and cant find a solution to the problem, also is there a better way to reduce the quality of my extracted frames ?

  thanks

• Scaling an image according to audio (threshold, frequencies)

  11 juillet 2022, par UnlockeerFromFrance

  I am looking for scaling a PNG file according to an audio provided, a frequency range (20hz-1000hz for example) and a threshold, for a smooth effect.
For example, when there is a kick, scale go to 120% smoothly, I would like to make those audio visualizers such as dubstep, etc... where when kicks comes in, their image are "pumping".
First, is it doable with ffmpeg ?
Where to start ?
I found showcqt that takes frequencies in input etc., but its output is a video so I don't think I can use it in my case. Any help appreciated.

  


• FFMPEG Image to video zoompan starting position

  4 août 2018, par lchn

  In creating mp4 slideshows out of images, I’ve taken some examples online for zoompan, but I still haven’t quite grasped how to make them start from a certain location in an image. Here’s the typical command :

  ffmpeg -i image-000.jpg -filter_complex "color=c=black:r=60:s=1920x1080[demo] ;[0:v]format=pix_fmts=yuva420p,scale=8000 :-1,zoompan=z=’min(zoom+0.0005,1.2)’:s=2000x1333:d=360:x=’if(gte(zoom,0.9),x,x+1/a)’:y=’if(gte(zoom,0.9),y,y+1)’,fade=in:0:25:alpha=1,setpts=PTS-STARTPTS+0.0/TB[v0] ;[demo][v0]overlay=format=yuv420"
   t 6 -c:v libx264 -y out000.mp4

  Photos I use are typically 3x2 or 4x3 in aspect ratio, so I get that they’d have to be cut off somewhere in a 16x9 video. The thing with the above code (and many other "Ken Burns effect" samples) is that they start with the bottom portion of the images cut off, then either zoom in more or zoom out, never showing the bottom.

  How do I get the animation to start further down on the image ? Nothing I do in the y=’...’ section affects it. Not even putting in constant numbers between 0 and 100000 instead of adjusting values in that formula y=’if(gte(zoom,0.9),y,y+1)’.

  Note : I’ve had some success using crop or pad for the original image, but I’d rather understand how to better position zoompan inside of the image.