ffmpeg videos join DTS in output stream 0:0

[grabyea]

hello i uae ffmpeg to join videos

this command im using

ffmpeg -f concat -i mylist.txt -c copy output.mp4

in mylist.txt i have 4 videos which i want to join in 1 video

file '1.mp4'
file '2.mp4'
file '3.mp4'
file '4.mp4'


[mov,mp4,m4a,3gp,3g2,mj2 @ 000001f6879f2440] Auto-inserting h264_mp4toannexb bitstream filter6x
[mp4 @ 000001f68796ab00] Non-monotonous DTS in output stream 0:0; previous: 83197350, current: 83196000; changing to 83197351. This may result in incorrect timestamps in the output file.
[mov,mp4,m4a,3gp,3g2,mj2 @ 000001f687feb3c0] Auto-inserting h264_mp4toannexb bitstream filter8x
[mov,mp4,m4a,3gp,3g2,mj2 @ 000001f6881f75c0] Auto-inserting h264_mp4toannexb bitstream filter5x
frame=94568 fps=11910 q=-1.0 Lsize= 2187593kB time=00:52:32.26 bitrate=5685.0kbits/s speed= 397x
video:2107210kB audio:75658kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.216478%


quality/size all good but 1 second out of sync in output video

out of sync could be because of this error?

"mp4 @ 000001f68796ab00] Non-monotonous DTS in output stream 0:0; previous: 83197350, current: 83196000; changing to 83197351. This may result in incorrect timestamps in the output file"



any solution?

[jagabo]

If the sync problem is constant (the sync is 1 second off all through the video) you can add an audio delay or advance (negative delay).

https://ffmpeg.org/ffmpeg.html (search for itsoffset)
https://trac.ffmpeg.org/wiki/UnderstandingItsoffset

I don't know how to do this while concatenating but you could do it with a second call to ffmpeg with the output from the first:

ffmpeg -f concat -i mylist.txt -c copy intermediate.mp4
ffmpeg -i intermediate.mp4 -itsoffset 1.00 -i intermediate.mp4 -map 0:v -map 1:a output.mp4