Re: slices

On Thu, 12 Feb 2004 18:13:02 -0500
D Richard Felker III <[email protected]> wrote:

> Consider vf_expand with osd rendering. You want to alpha-blend osd
> onto the image during the slice rendering, so you don't have to read
> video memory later to add osd! But here you run into a big problem.
> Slice rendering takes place in decoding order, whereas osd contents
> will be known in display order. It would look really stupid for the
> clock to jump backwards for one frame, etc. How do we solve this??

I wouldn't mind that. There is at least one subtitle format
around that does not require time sorted entries, thus the osd
reader/renderer needs to sort and chache them anyways.
And i'm sure there are more such stupid formats out there. [1]

Also i think even if we leave those fileformats aside and
only look at odered subs (ie by preordering those shit formats)
it's still not hard to provide a few frameduration long backlog
of subtitles [2].

But, the more important question here is, how do you plan
to integrate the subtitle renderer into your vp/vo design ?
The current "every vo needs draw_alpha" doesn't work quite
well as we all know. Beside i'd like to have colored subs
with any shape. One stupid solution would be to do everything
in a vp_expand, but then we'd lose potential acceleration by
the graphics card for alpha only subs (or is there also a way
for fast coloured subs rendering ?)


[1] There are a few more issues here as it's not always possible
to read the whole subfile at once as it might be a stream
embeded in ogm/mkv/nut/whatever file or come over a network
stream. 

[2] This rises of course the question of how many consecutive
B frames are allowed/possible. So far i haven't seen more
than 2 consecutive B frames, but that doesn't mean someone
outthere thinks he could encode a file consisting of
one I frame at the beginning, a P frame at the end and
the whole rest constisting of B frames.


			Attila Kinali
-- 
egp ist vergleichbar mit einem ikea bausatz fuer flugzeugtraeger
			-- reeler in +kaosu