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• FFmpeg timestamp watermark beginning at a specified offset [closed]

  12 mai 2023, par Marcipicus

  I am trying to extract a portion of video from another video file.

  


  I want the second video file to be timestamped with the time in the original file from which the excerpt was extracted.

  


  Here is the command so far.

  


  #FILE TIME WATERMARK
    ffmpeg -ss "$startSecond" -i "$inputFile" -to "$endSecond" -vf "drawtext=text='%{pts\:hms}':fontfile=FreeSerif.ttf:fontsize=20:x=40:y=60:box=1:boxcolor=white@0.5:boxborderw=5" -c:v libx264 -crf 23 -preset medium -c:a libmp3lame -q:a 2 "$outputFile"


  


  That part already works but the timestamp begins at 0 seconds.

  


  How do I modify the command to begin the timestamp at the value in $startSecond ?

  


  I tried the following command.

  


  ffmpeg -ss "$startSecond" -i "$inputFile" -to "$endSecond" -vf "drawtext=text='%{pts+$startSecond\:hms}':fontfile=FreeSerif.ttf:fontsize=20:x=40:y=60:box=1:boxcolor=white@0.5:boxborderw=5" -c:v libx264 -crf 23 -preset medium -c:a libmp3lame -q:a 2 "$outputFile"


  


  The only difference is that I added the value of $startSecond to pts.

  


  I couldn't find the documentation on the timestamping method for the drawtext filter. If anyone can find it I would appreciate it.

  


• FFMPEG Encoding to prores 4444 with alpha doesn't retain original alpha [closed]

  19 mai 2023, par Nick Weeden

  I'm trying to convert an rgba png to prores 4444 with an alpha. When I run the following command it will create prores file with an alpha. But, the alpha is full white, it doesn't retain the values I put in.

  


  ffmpeg -start_number 1001 -r 24.000 - "pngWithAlpha_%06d.png" -c:v prores_ks -profile:v 4 -alpha_bits 16 -y "proresWithAlpha.mov"


  


  I've tried this with both FFMPEG 4.2.2 and 6.0.0 on a linux system, I'm not sure if I'm doing it wrong or if it is a bug.

  


  Looking at this post it seems it should be possible (they're complaining about quality not a fully missing transfer of the alpha).

  


  I would expect it to pass the alpha straight through but it doesn't. I used alpha_extract to copy the alpha in to the rgb to confirm I'm able to read the alpha from the png, which worked. But the alpha was still full white.

  


• FFMPEG video (mp4) to image sequence with the time in the filename [closed]

  7 juin 2013, par Ewald Bos

  i have a question and can't find the answer perhaps you can help ?

  I am using FFMPEG (windows enviroment) and convert a video (mp4) to a series of images based on scene detection (i-frames) and add the timecode inside the image (burn) like this ;

  ffmpeg -i video.mp4 -vf "drawtext=fontfile=trebucbd.ttf: timecode='00\:00\:00\:00': r=25: x=(w-tw)/2: y=h-(2*lh): fontcolor=white: box=1: boxcolor=0x00000000@1, select=eq(pict_type\,I)" -vsync 0 -an iframes/%06d.jpg

  All this works perfect but i also would like to add the timecode in the filename, so instead of naming it 000001.jpg, 000002.jpg i would like to have 00.00.00.01.jpg, 00.00.00.17.jpg and thoughts about this ?