[FFmpeg-user] Selecting/dropping frames without re-encoding

[Marton Balint]

On Wed, 5 Oct 2016, Mikhail V wrote:

> On 5 October 2016 at 19:55, Carl Eugen Hoyos <ceffmpeg at gmail.com> wrote:
>> 2016-10-05 15:45 GMT+02:00 Mikhail V <mikhailwas at gmail.com>:
>>
>>> Is it possible that ffmpeg cannot do this without re-encoding?
>>
>> You can export single frames and delete half of them using a
>> shell script.
>>
>> Carl Eugen
>
> Sure I can :) Also I can just directly recode it in 25 fps in any codec.
> So I suppose the answer is - I can't do it without re-encode.
> I was just wondering why there is no such function for intraframe codecs,
> would be very handy in my opinion.

You may try generating an ffconcat file which seeks to every second frame, 
then force the halved frame rate for it, finally mux this with the 
original audio using streamcopy. With a little luck, this should work.

Regards,
Marton