[MPlayer-users] ssa/ass rendering uses lots of cpu with -vo gl

Vladimir Mosgalin mosgalin at VM10124.spb.edu
Sat Jan 29 20:27:53 CET 2011

Hi Reimar Döffinger!

 On 2011.01.26 at 22:03:33 +0100, Reimar Döffinger wrote next:

> > Is it some unvoidable nature of libass rendering that one has to upload
> > glyphs many times, one by one to the video card? Or you want to say that
> > merely trying to render glyphs one by one into texture that's yet to be
> > uploaded causes slowdown already?
> > 
> > Could it be possible to "compact" all the glyphs into yet to be uploaded
> > texture as a mere image, without using opengl texture functions loading
> > texture into vram? So to say, "-vf ass" like rendering into transparent
> > high resolution texture, which is then layered on the main video texture
> > in one pass? Or it's too complicated..
> Depends on what you mean. If you mean a texture of the same size as the
> image: in principle that's possible but it has issues like huge
> GPU memory usage, problems with rendering of overlapped parts, probably
> higher CPU usage for simpler things and it simply can't work with PCI
> video cards (at 1080p the current OSD needs maybe 60 MB/s bandwidth,
> whereas that approach would need almost 200 MB/s which without video
> is already more than PCI can do).
> -vo direct3d does it that way if I remember right.

Well not exactly, texture of image size will be no better than -vf ass:
bad font quality for SD video, it must be always 4096x4096 texture, or
full screen size texture, or something. bandwith might be the problem,
idk, an option to use compressed texture could help?.. Though yes it
all seems complicated.

It's most likely impossible to watch 1080p even without subtitles on PCI
video card btw, last time I hooked up PCI card to powerful PC i had
trouble even watching 720p, and there are hardly any PCI cards where gl
driver will give any benefit compared to, say, xv.

At times I really wish mplayer had some condition-style configuration,
to set configuration of video filters automatically depending on
resolution.. This could've solved quite a few problems, like setting
different filters or video output driver for 1080p and the rest but is
probably too big of a change.



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