I have been struggling with this one for quite some time as well. This ffmpeg option yielded proper iOs synchronization both during concatenation and afterwards when re-encoding the already concatenated file. I don't know if this setting is optimal, but the result was a mp4 with audio and video remaining synchronized when played by both iOs and VLC. By playing the same movie simultaneously in both iOs and Windows VLC, and initially synchronized with each other as well as I could, by observing the evolution of the 'echo' between them, I concluded that the iOs audio was going too fast (assuming the Windows player is correct).įor me, the solution was to add the audio filter option -af aresample=async=1000 to the ffmpeg command, which I found as an example in the ffmpeg online documentation and used verbatim. Interestingly, the sync could be restored temporarily by advancing the movie progress slider to any point in the movie, but then the sync would be lost again as the movie continued to play in iOs. The symptom for iOs playing this concatenated mp4 was initially good synchronization followed by an increasing loss of synchronization as the movie played, with audio going faster than video. In my case, I was also concatenating files, and found audio/video sync problems with iOs, but not with Windows (e.g., VLC media player showed no synchronization problems using the same mp4 file). I encountered a similar problem and found a solution that worked, at least for me. Where segments.txt consists of the names of the padded files. Step 2 Concat ffmpeg -f concat -i segments.txt -c copy test.mov Generate segments with synced streams ffmpeg -y -ss 00:00:02.750 -i input.MOV -c copy -t 00:00:05.880 -avoid_negative_ts make_zero -fflags +genpts segment.MOV Step 1 Pad out the audio in each segment ffmpeg -i segment1.mov -af apad -c:v copy -shortest -avoid_negative_ts make_zero -fflags +genpts padded1.mov

Ffmpeg concat video and keep audio