[FFmpeg-user] IDR frames

[Andrew Randrianasulu]

чт, 4 июл. 2024 г., 02:39 Mark Filipak <markfilipak.imdb at gmail.com>:

> H.264 appears to have made I- P- & B-frames obsolete.
>
> Everyone's probably seen my DTS-PTS diagrams.
>
> Closed GOP
> PTS order     I  B  B  P  B  B  P..
>               /  ______/  ______/
>              /  /        /
> DTS order  I  P  B  B  P  B  B..
>
> Open GOP
> PTS order     ..B  B  I  B  B  P..
>                 ______/  ______/
>                /        /
> DTS order  ..I  B  B  P  B  B..
>                 open Bs
>
> where the open Bs are actually part of the previous GOP.
>
> Well, H.264 references the past & future in the same way, but on a
> picture-slice basis. There are
> I-slices, P-slices, and B-slices. The way to visualize that is to imagine
> that above the I- P- &
> B-frames you can see the frame's slices. Imagine there are links for those
> slices to past & future
> slices in other frames, even 'crossing' an I-frame's PTS.
>
> Such a diagram would look like a spider web with many lines going every
> which way from every frame.
>
> An IDR frame is an I-frame where the spider web is collapsed/missing on
> its left (in the past) so
> that no I-frame slices reference any slices in the past, and likewise for
> all the P- & B-frames to
> the I-frame's right.
>
> That effectively means there are only two types of frames: IDR and
> non-IDR. That effectively
> obsolutes P- & B-frames -- they no longer have any meaning.
>
> If I am wrong, please let me know. It's what I've sussed out from H.264,
> but H.264 is not human
> readable.
>
> --Mark.
>


I also noticed some new answers at

https://github.com/mifi/lossless-cut/issues/126#issue-comment-box

discussing -segment command line switch for ffmpeg for cutting mp4 video.

https://github.com/mifi/lossless-cut/issues/126#issuecomment-2059432251

note that this only said to be working for mp4 container and not matroska.







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