[FFmpeg-devel] [FEATURE] Cut a video (-ss) with timings non-aligned on keyframes, with minimal re-encoding

[Michael Niedermayer]

On Tue, Aug 20, 2024 at 02:36:53PM +0200, Lynne via ffmpeg-devel wrote:
> On 20/08/2024 14:13, basj at gget.it wrote:
> > > > More generally, which is the recommanded way to cut a video with a specific starting point and specific length, with minimal re-encoding?
> > > > Millions of hours of CPU-time are probably wasted to reencode already-perfectly-encoded content, just for cutting ;)
> > > 
> > > Only do remux without transcoding, and let mp4 muxer use editlist to strip the timeline from IDR to the requested start time.
> > > The preroll at the beginning can be slow when playback, but seeking also has the same preroll
> > > 
> > > Other choice is use multiple groups of SPS/PPS in mp4 sample description. We have that support in mp4 demuxer, but not
> > > in muxer. It’s standard in specification but not widely supported. So if we add support to muxer and it works with our own
> > > demuxer, it’s not surprise to experience a lot of compatibility issues with other software.
> > 
> > Thank you Zhao for your answer.
> > 
> > Is there a feature already available in ffmpeg to use one of your 2 solutions?
> > Or is someone already working on this topic? (if so, can I join this feature development?)
> > 
> > In any case, if someone has a solution, many people are looking for a solution for this, either here: https://stackoverflow.com/questions/63548027/cut-a-video-in-between-key-frames-without-re-encoding-the-full-video-using-ffpme (closed),
> > or here: https://superuser.com/questions/1850814/how-to-cut-a-video-with-ffmpeg-with-no-or-minimal-re-encoding.
> > It would help many people if a ffmpeg-expert could help on this :)
> 
> AVTransport, the new container I'm working on, supports more flexible
> signalling of decoded but discarded refs. Still WIP so no support for it in
> FFmpeg, but hopefully not for too long.

Please dont add a new container. Such signalling can be added to
existing containers with little effort.
Iam also happy to help to add it to nut

reminded me of this:
https://xkcd.com/927/

thx


[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Dictatorship naturally arises out of democracy, and the most aggravated
form of tyranny and slavery out of the most extreme liberty. -- Plato
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