[FFmpeg-devel] [PATCH] libavcodec: add bit-rate support to RoQ video encoder

[Victor Luchitz]

On Thu, Jan 25, 2024 at 1:27 AM Tomas Härdin <git at haerdin.se> wrote:

> tor 2024-01-25 klockan 01:09 +0300 skrev Victor Luchitz:
> > In our case, the machine we're targeting (the Sega 32X) has only
> > 256KB
> > of RAM. Even more modern consoles such as XBOX or even PS3 didn't
> > have enough RAM to hold an entire CD-ROM..
> >
> > We also have to be concerned about how fast we can move data to the
> > main CPU. Say you make the first frame BIG to make it look its best,
> > then
> > compensate with much smaller delta frames... is the first frame too
> > much
> > data to move to the CPU quick enough? Well, maybe not an issue for
> > the
> > first frame, but definitely an issue for keyframes in the middle of
> > the
> > stream.
>
> Ah, that makes a lot more sense. Yeah I can see that being an issue.
> And decoding time probably depends on packet size as well, so even if
> you could move data around in advance, this still doesn't help that
> keyframe decode any faster. I've seen similar behavior with JPEG2000
> where decode time scales linearly with bitrate (plus a fixed overhead).
>
> One thing that strikes me is if you're only aiming for linear playback
> then you can set the GOP size large enough that the encoder is never
> forced to insert a keyframe.
>
> I think my main issue then comes down to the qscale search being way
> too slow, especially the fact that it can effectively hang. I would
> suggest a binary search using the heuristic I derived for the first
> split, or something similar. Searching between 1 and 100000000 seems
> excessive in most cases. It should be possible to box that interval in
> quickly, again using the heuristic.
>

Alright, we'll look into it, thanks!


>
> /Tomas
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-- 
Best regards,
 Victor Luchitz