[FFmpeg-user] ct a video precisly

[Henk D. Schoneveld]

On 16 Sep 2015, at 12:39, Robert Krüger <krueger at lesspain.de> wrote:

> 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.
I don’t see the difference, although I didn’t explicitly mention that this is done in 1 step.
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