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• ffmpeg - convert background to black ? [closed]

  22 juin 2022, par david furst

  the basic problem
  
convert all pixels in all frames of a source video to black if they have a white value below a certain threshold and output the results as a series of static images with no transparency.

  


  my solution so far
  
i am able to do this with a two-step process :

  


  

  1. convert pixels below the threshold to transparent using ffmpeg's colorkey filtre, outputting a series as PNG.

  


  2. use imagemagick to convert the PNG to JPEG.

  


  


  this approach is very slow. ideally i'd like to do everything in one go, within ffmpeg.

  


  the reason i haven't been able to do that so far is that the resulting transparency isn't discarded (as i'd hoped) when outputting to non-transparent formats like JPG, even if i try to 'discard' the alpha layer beforehand using combinations of split and lutrgb ; the resulting JPEGs still resemble the original images.

  


  my current filter chain :

  


  ffmpeg -hide_banner -y -i input.mp4 -f lavfi -i color=c=white \
    -filter_complex "[0:v]format=gray[src];
        [1][src]scale2ref[white][vid];
        [vid][white]blend=all_mode=multiply:shortest=1,colorkey=black:0.95" %05d.png


  


• ffmpeg not creating audio file

  13 février 2015, par Dries

  I’m trying to write raw s16le audio to an audio file using ffmpeg.
  This is the command I’m using :

  ffmpeg -y -f s16le -acodec pcm_s16le -ar 44100 -ac 1 -i - -vn -ar 44100 -ac 1 OUTPUT_FILE.wav

  After this command is handled I use stdin to put data in the encoder like this :

  fwrite(samples_, sizeof(short int*), numSamples, audioffmpeg); 

  where samples_ is a short int* with a number of numSamples combined. At the moment I’m trying this per sample (so numSamples is 1).

  For some reason this isn’t creating a new file. Although, when I use a previously created file as input (so I don’t use stdin) it does create a new file.

  FFmpeg doesn’t seem to be outputting so I can’t give that

• Libx264 width not divisible by 2

  1er mai 2022, par Meh Sadness

  I have this ffmpeg command :

  


  ffmpeg -framerate 1 \
-i \"path/to/background\" \
-i \"path/to/source/mp3\" \
-filter_complex \"[1:v]scale=600:-1, pad=(16/15)*iw:(16/15)*ih:(ow-iw)/2:(oh-ih)/2:white, [0:v]overlay=(W-w)/7:(H-h)/2:shortest=1,drawtext=fontsize={fontsize}:fontfile={font}:fontcolor=white:text=\'{artist} - {title}\':x=W/2+W/10.5:y=H/11,drawtext=fontsize={fontsize}:fontfile={font}:fontcolor=white:text=\'{album}\':x=W/2+W/10.5:y=2*(H/10),drawtext=fontsize={fontsize}:fontfile={font}:fontcolor=white:text=\'{date}\':x=W/2+W/10.5:y=3*(H/10),format=yuv420p\" \
-c:v libx264 \
-r 30 \
-movflags +faststart \"{output}\"


  


  It should convert the music into a video that will contain the cover art and various metadata.

  


  However, I am getting the error indicated in the title and, at the same time, various changes to the pad and scale filter unfortunately didn't work. Moreover, no matter what part of the command I change, I still get an error like this :

  


  [libx264 @ 000001581b1d7b80] width not divisible by 2 (555x260)


  


  And at the same time, the dimensions are always the same - 555x260