Use the color source filter to make the 15 second, 24 fps, 1280x720 black video and append it to the end of the main video with the concat filter: ffmpeg -i main.mkv -filter_complex 'color=c=black:s=1280x720:r=24:d=15 concat=n=2:v=1:a=0' -map '' output.mkv Con: Filtering requires encoding, so no stream copying of the main video as in the concat demuxer.file 'main.mkv'Ĭoncatenate: ffmpeg -f concat -i input.txt -c copy output.mkv The order in this text file determines the order that they will appear when concatenating. This example makes a 15 second black video, frame rate of 24, size is 1280x720: ffmpeg -f lavfi -i color=c=black:s=1280x720:r=24:d=15 black.mkv Make the black video using same attributes and same number and type of streams as the main input. Harder to get right, because the blank video needs to have the same attributes as the main video. Pros: Avoids re-encoding the main video and therefore preserves quality since it is stream copied.I read in the documentation that this can happen with 'non-intra frame codecs' because 'for non-intra frame ones you will usually get extra packets before the actual In point and the decoded content will most likely contain frames before In point too. With the contents of concatSpecs.txt like so: file 'a.avi'įfprobe output.avi gives me: Input #0, avi, from 'output.avi':ĭuration: 00:00:12.00, start: 0.000000, bitrate: 1014 kb/s I'm running this command ffmpeg -f concat -i concatSpecs.txt -vcodec copy -acodec copy output.avi In the example below, I'm trying to merge three 2-second clips, but I get a video that is 12 seconds long, instead of 6 seconds. I'm trying to cut/merge multiple videos using the concat demuxer method, but the resulting video has too many frames from each of the input videos.

Ffmpeg concat demuxer duration