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

[Marton Balint]

On Fri, 7 Oct 2016, Moritz Barsnick wrote:

> On Fri, Oct 07, 2016 at 13:07:53 +0200, Carl Eugen Hoyos wrote:
>> 2016-10-06 17:34 GMT+02:00 Moritz Barsnick <barsnick at gmx.net>:
>> > $ ffmpeg -r 25 -f concat -i concatscript.txt -c:v copy output.mxf
>> 
>> This scales very badly, no?
>
> It's just a proof of concept. :) It scales nicely (linearly? or is
> seeking more expensive the deeper you seek?), and works assuming you
> have CFR input and output, and you know those rates, and ... , and ...
> ;-)

Scaling issues are probably caused by the fact that the concat demuxer 
reopens the file for each frame, instead of detecting that the next 
segment is referring to the same file as the previous one. Probably not 
too hard to improve the concat demuxer to detect such cases and avoid 
reopening the source.

Regards,
Marton