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• FFMPEG Layering two .mov files color issue

  21 February 2023, by JDC

  I have two folders containing numbered .mov files all the same length, one folder for front and one for back. I'm using ffmpeg to combine the front and back videos with matching numbers into one output video (the front video has an alpha channel). The below command works, but in the output video the front layer has slightly incorrect colors compared to the input (reds are too yellow for example). The back layer in the output looks correct. Both input files use the bt709 color space (checked with ffprobe). Is there something in the overlay options which is causing the front layer to look incorrect, or something I'm doing wrong with the colorspace options?

  


  


  for f in Video_Back/Video_Back_*.mov; do
num=$(echo "$f" | sed -n 's/.*Video_Back_([0-9]5).mov$/\1/p')
if [ -f "Video_Front/Video_Front_$num.mov" ]; then
ffmpeg -color_primaries bt709 -color_trc gamma28 -colorspace bt709 -i "$f" -color_primaries bt709 -color_trc gamma28 -colorspace bt709 -i "Video_Front/Video_Front_$num.mov" -filter_complex "[1:v]format=rgba[fg];[0:v][fg]overlay=shortest=1:alpha=straight,eq=gamma=1.0[mixed]" -map "[mixed]" -map 0:a:0 -c:v libx264 -crf 18 -preset veryfast -c:a copy "Video_Merged/Video_Merged_$num.mp4"
fi
done

  


  


• FFmpeg Command Combinations

  1 September 2015, by alr027

  I’m trying to add an mp3 overlay to an mp4 video with it’s own audio track using FFmpeg. I want to keep the original audio as well as the new one. The only way I found is to strip the audio from the original video, combine it with the mp3 file, and then combine that file back with the mp4:

  1) ffmpeg -i video.mp4 1.mp3

  2) ffmpeg -i audio.mp3 -i 1.mp3  -filter_complex amerge -c:a libmp3lame -q:a 4 audiofinal.mp3

  3) ffmpeg  -i videofinal.mp4 -i audiofinal.mp3 -shortest final.mp4

  That is a fine way of doing it and it works but I have to run my files back and forth through FFmpeg way too many times. How can I write one text file to run all three of these commands in sequence?

  Note: I’m using Windows.

• Use ffmpeg to time-dilate and resample audio without changing frequencies

  18 May 2018, by Adisak

  I have some audio (wave file) that is sampled at a rate of 48000 samples per second.

  This audio was created to match a 30 FPS video. However, the video actually plays back on the target at the NTSC framerate of 29.97 (30 X 1000/1001).

  This means that I need to time-dilate the audio so that there are 48048 samples where there were previously 48000 samples (it plays back 1.001 times slower) but still maintains that the final audio file’s rate is 48000 samples per second.

  Ideally, also, I’d like to do this resample using the sox library option for FFMPEG since I hear it has much higher quality.

  Can anyone help me with the command line necessary to process a file in this manner?