FFmpeg concatenation changes the duration and playback speed of the input videos

Question

I have two input videos that I am concatenating using the FFmpeg concat demuxer:

ffmpeg -f concat safe \'0\' -i /path/to/file.txt -c copy /path/to/output.mp4         


        

Answer 1

The first video has a smaller timebase (and no audio track). Rewrap it like this and then concat:

ffmpeg -i 16382802.mp4 -f lavfi -i anullsrc -c:v copy -video_track_timescale 30k -c:a aac -ac 6 -ar 44100 -shortest new.mp4