[FFmpeg-user] ct a video precisly

[Robert Krüger]

On Wed, Sep 16, 2015 at 12:26 PM, Henk D. Schoneveld <belcampo at zonnet.nl>
wrote:

>
> On 16 Sep 2015, at 11:33, gagall at free.fr wrote:
>
> > Hello,
> >
> > I'm trying to cut a video to get 12s sequences. It needs to be accurate.
> Cutting is done on begin and end of a Group Of Pictures, a GOP.
> Splitting always occurs the way you mention, it is ‘about 12 seconds’
> What is, could be the reason, you need it absoute accurate ?
> One way around could be to 1st encode your source to all I-frame, key
> frames. This way you get a GOP-size of 1


That's not necessary. AFAIR ffmpeg will subclip accurately also for
non-i-frame-only codecs when transcoding the video. So if your aoutput is
not supposed to be i-frame-only (which is probably not the case), you would
have an unneeded encoding step (and thus quality loss), unless your
intermediate format is lossless of course. So, should it not suffice to
replace copy by a re-encoding, you could do that as a workaround (i.e.
transcode to ffv1-iframe-only and then segment that) but as I said, it
should not be required.