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

Nicolas George nicolas.george at normalesup.org
Mon Jan 17 14:06:12 CET 2011

L'octidi 28 nivôse, an CCXIX, Vladimir Mosgalin a écrit :
> I just noticed some strange thing; rendering .ass with effects consumes
> insane amount of processing power with -vo gl target (i'm using -vo
> gl:yuv=2, but any -vo gl mode has problems)
> I'm talking about fansubbed anime, which uses karaoke effects in
> opening. 1920x1080 resolution, this file was unplayable in some moments

What kind of effects are they exactly. ASS subtitles on most VOs renders the
subtitles for each frame, but the rendering is reasonably cheap. For GL, on
the other hand, there are two phases : the subtitles are uploaded when each
time the subtitles change, and overlaid on each frame. The overlay is cheap,
the upload is more costly.

Depending on the kind of effects, each single frame may need an upload.

> I can give link to .torrent with that file or upload opening (~300 mb)
> or .ass subtitle file that's used, if it's needed.

The ASS file, and even only an excerpt of it, would be enough, provided you
can reproduce the slowness on a black frame (-demuxer rawvideo /dev/zero).
You can accentuate the problem by enlarging the font, adding more text and
heightening the framerate if necessary.


  Nicolas George

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