[SOLVED] [ffmpeg] Why does it ignore the -to switch?

[yetanotherlogin]

Hello

I'm using the latest and greatest (ffmpeg N-79690-g78baa45).

For some reason, the following doesn't work as expected: Instead of slicing the video after 5mn, it keeps going for 10:

ffmpeg -ss 00:15:17 -i input.mp4 -to 00:20:17 -c copy -threads 2 -f mp4 output.mp4

Same result:

ffmpeg -ss 00:15:17 -i input.mp4 -to 00:20:17 -c:v libx264  -pix_fmt yuv420p -c:a copy -threads 2 -f mp4 output.mp4

Any idea why? Did the ffmpeg team changed the meaning of the -to switch?

Thank you.

[racer-x]

Try:

ffmpeg -ss 00:15:17 -i input.mp4 -t 00:05:00 -c copy -threads 2 -f mp4 output.mp4

[JVRaines]

I find that -to only works when -ss is entered as an output option.

[yetanotherlogin]

Thanks. I don't want to use the -t option because the -to option lets me just type the end of the segment without having to compute how long it lasts.

Why does it matter where I put the -ss and -to options?

Here, they're put before the -i option:
http://ffmpeg.io/howto

Here, they're after:
http://stackoverflow.com/questions/18444194/cutting-the-videos-based-on-start-and-end-...e-using-ffmpeg
---
Edit: Here's the explanation:
https://trac.ffmpeg.org/wiki/Seeking

[MaxDB]

"Thanks. I don't want to use the -t option because the -to option lets me just type the end of the segment without having to compute how long it lasts. Why does it matter where I put the -ss and -to options?"

The -ss option can be either an input option or an output option. The -to option and -t option are only output options.

If you use -ss and -to both on the output, then -to will work as you expect. The downside is that it will filter and encode all of the frames from the beginning of the file, then throw them out until the start time in -ss. Just a timewaster, but -to then works.

If you use -ss before -i, then those frames are thrown away before processing, so the output never sees those frames. So as far as the -to can tell, the video is that much shorter and started at 0, instead of started at the -ss time.

Want a clip from src video that starts at 2:30 and ends at 7:30...

ffmpeg -i src.mpg <encode options> -ss 00:02:30 -to 00:07:30 dst.mpg

ffmpeg -i src.mpg <encode options> -ss 00:02:30 -t 00:05:00 dst.mpg
ffmpeg -i src.mpg <encode options> -ss 00:02:30 -t 300 dst.mpg

ffmpeg -ss 00:02:30 -i src.mpg <encode options> -t 300 dst.mpg

All but the last command process frames from the start of the file then drops them in the very last step before writing; the last command instead throws out those frames (very quickly) before processing and starts processing frames beginning with the -ss time.


ffpmeg

[Budman1]

It doesn't matter if you use -t it - to. If you use -ss as an input it resets the timecode to 0 so -t and - to then means to a point from the ss point starting at 0. It is further complicated by the fact that if you use -c copy, ffmpeg will cut at a key frame but your first frame may not have a timecode of 0. This may play ok on some players but give problems if you try to merge it to another segment, even with the same parameters.

There is a way to do it with -vframes that works but it is tricky also.