[SOLVED] Why does ffmpeg keep going past the length of the video?

[yetanotherlogin]

Hello

I tried the following command to split an MP4 video exactly, which means re-encoding the video stream, while keeping the audio as-is since it was good enough:

ffmpeg -ss 02:34:48 -i input.mp4 -b:v 200k -t 02:51:40 -c:v libx264 -vf scale=640:-1 -pix_fmt yuv420p -c:a copy -shortest -threads 2 -crf 20 -f mp4 output.mp4

Even though I used the "-shortest" option, ffmpeg keeps going past the length of the video (which is about 15mn, and I stopped ffmpeg at around 23mn).

Does someone why, and if there's a way to avoid needlessly re-encoding the audio stream as well?

Thank you.

--
Edit : I tried the "-to" option introduced in 2013, to no avail:

ffmpeg -ss 02:34:48 -i input.mp4 -b:v 200k -to 02:51:40

[Baldrick]

Are you sure you are using a newer version of ffmpeg? Use ffmpeg -version

I guess you have read http://trac.ffmpeg.org/wiki/Seeking ?

[yetanotherlogin]

Yes, I'm using the latest and greatest.

I don't understand what this means:
"Note that if you specify -ss before -i only, the timestamps will be reset to zero, so -t and -to have not the same effect. If you want to keep the original timestamps, add the -copytsoption."

[Selur]

You put '-ss 02:34:48' before the input thus ffmpeg starts at that point and the internal time stamp is now 0 at that point, so if you want to reencode from 02:34:48 to 02:51:40 you want to encode an interval of 00:16:52 and thus you should set the duration to 00:16:52 (-t 00:16:52).

[yetanotherlogin]

Thanks for the info.

This worked as expected:

ffmpeg -i input.mp4 -ss 00:05:00 -b:v 200k -to 00:05:30 -c:v libx264 -vf scale=640:-1 -pix_fmt yuv420p -c:a copy -shortest -threads 2 -crf 20 -f mp4 output.mp4