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

[Mikhail V]

On 6 October 2016 at 10:07, Carl Eugen Hoyos <ceffmpeg at gmail.com> wrote:
> 2016-10-05 23:08 GMT+02:00 Mikhail V <mikhailwas at gmail.com>:
>> 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.
>
>> 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.
>
> If you want to drop every second frame without re-encoding at
> all, you can export all frames as single frames and use a shell
> script to drop half of them.

I admit I am not fully getting your idea then. I want the output as
same video file.
If I export as images then it is just a folder with images. Yes they
will be not changed,
but if I want them back in a DNxHD video file, how can I guarantee
that the information
will be not changed due to compression? Do you mean this is possible somehow to
put the images back in video file without touching the image information?