Non-monotonous DTS in output stream previous current changing to This may result in incorrect timestamps in the output file

Question

I am having a file.txt with rather close snippets

file 'input.mp4'
inpoint 1.5402465510368346
outpoint 2.722609395980835
file 'input.mp4'
inpoint 3.192511146068573
outpoint 7.074568028450012
file 'input.mp4'
inpoint 7.851800565719604
outpoint 9.023683423995971
file 'input.mp4'
inpoint 10.054571752548219
outpoint 12.008032734394073
file 'input.mp4'
inpoint 18.70977670431137
outpoint 21.20993923664093
file 'input.mp4'
inpoint 24.51183382153511
outpoint 26.465287650823594
...

I concat them with

ffmpeg -safe 0 -f concat -i file.txt out.mp4

and I tried

ffmpeg -use_wallclock_as_timestamps 1 -safe 0 -f concat -i file.txt out.mp4

Yet I get

[mp4 @ 00000178c514cc00] Non-monotonous DTS in output stream 0:1; previous: 2069, current: 2067; changing to 2070. This may result in incorrect timestamps in the output file.
[mp4 @ 00000178c514cc00] Non-monotonous DTS in output stream 0:1; previous: 2070, current: 2067; changing to 2071. This may result in incorrect timestamps in the output file.
[mp4 @ 00000178c514cc00] Non-monotonous DTS in output stream 0:1; previous: 2071, current: 2067; changing to 2072. This may result in incorrect timestamps in the output file.
[aac @ 00000178c50f8a80] Queue input is backward in time
[mp4 @ 00000178c514cc00] Non-monotonous DTS in output stream 0:1; previous: 2758, current: 2756; changing to 2759. This may result in incorrect timestamps in the output file.
[aac @ 00000178c50f8a80] Queue input is backward in time
    Last message repeated 5 times
[mp4 @ 00000178c514cc00] Non-monotonous DTS in output stream 0:1; previous: 7581, current: 7579; changing to 7582. This may result in incorrect timestamps in the output file.
[aac @ 00000178c50f8a80] Queue input is backward in time
[mp4 @ 00000178c514cc00] Non-monotonous DTS in output stream 0:1; previous: 7582, current: 7579; changing to 7583. This may result in incorrect timestamps in the output file.
[aac @ 00000178c50f8a80] Queue input is backward in time
[mp4 @ 00000178c514cc00] Non-monotonous DTS in output stream 0:1; previous: 7583, current: 7579; changing to 7584. This may result in incorrect timestamps in the output file.
[aac @ 00000178c50f8a80] Queue input is backward in time
[mp4 @ 00000178c514cc00] Non-monotonous DTS in output stream 0:1; previous: 7584, current: 7579; changing to 7585. This may result in incorrect timestamps in the output file.
[aac @ 00000178c50f8a80] Queue input is backward in time
[mp4 @ 00000178c514cc00] Non-monotonous DTS in output stream 0:1; previous: 7585, current: 7579; changing to 7586. This may result in incorrect timestamps in the output file.
[aac @ 00000178c50f8a80] Queue input is backward in time
[mp4 @ 00000178c514cc00] Non-monotonous DTS in output stream 0:1; previous: 7586, current: 7579; changing to 7587. This may result in incorrect timestamps in the output file.
[aac @ 00000178c50f8a80] Queue input is backward in time
[mp4 @ 00000178c514cc00] Non-monotonous DTS in output stream 0:1; previous: 7587, current: 7579; changing to 7588. This may result in incorrect timestamps in the output file.
[aac @ 00000178c50f8a80] Queue input is backward in time
[mp4 @ 00000178c514cc00] Non-monotonous DTS in output stream 0:1; previous: 7588, current: 7579; changing to 7589. This may result in incorrect timestamps in the output file.
[mp4 @ 00000178c514cc00] Non-monotonous DTS in output stream 0:1; previous: 7589, current: 7579; changing to 7590. This may result in incorrect timestamps in the output file.
[aac @ 00000178c50f8a80] Queue input is backward in time
[mp4 @ 00000178c514cc00] Non-monotonous DTS in output stream 0:1; previous: 7590, current: 7579; changing to 7591. This may result in incorrect timestamps in the output file.
[aac @ 00000178c50f8a80] Queue input is backward in time

And the final file is cut at wrong places.

How to make the file.txt work?

Answer 1

The concat demuxer will select portions of the input outside the stated range if that portion is required for decoding purposes. These will cause a timestamp clash as well extra material in your output. You'll need to use the select filter to get rid of them.

ffmpeg -safe 0 -f concat -segment_time_metadata 1 -i file.txt -vf select=concatdec_select -af aselect=concatdec_select,aresample=async=1 out.mp4