[MPlayer-dev-eng] [PATCH] A new ASS renderer

[Clément Bœsch]

On Sat, Sep 22, 2012 at 09:01:40PM +0200, Reimar Döffinger wrote:
> On Sat, Sep 22, 2012 at 08:02:36PM +0800, Xidorn Quan wrote:
> > The patch attached is a new ASS renderer which is optimized for
> > subtitles with few effects. For me, this new renderer is nearly
> > 2x faster on average than the current one for those subtitles.
> > 
> > I found that most subtitles keep unchanged across several frames,
> > while vf_ass renders them over and over again for every images in it.
> > 
> > This new renderer renders that images to one image with alpha channal
> > when subtitle changes, then it simply does pixel weighted addition for
> > new frame and the image. The second step is very fast, cache-friendly
> > and easy to be further optimized, for example, by using SIMD.
> > 
> > In this patch, I moved get_image, blank, and prepare_image from
> > vf_ass.c to ass_common.c and color converting macros to ass_common.h
> > so that I can reuse them in vf_ass2.
> > 
> > To use this new renderer, just add "-vf ass2" to the comand line.
> 
> I strongly dislike both having and having to maintain two solutions
> to the same problem.
> One solution would be to switch between the methods based on some
> heuristics from e.g. the previous frames.
> I also kind of wonder what the use case is, where does ASS rendering
> speed make a relevant difference (while also none of the
> hardware-accelerated implementations are used)?

I'd unfortunately say that ASS performance is relevant when rendering
complex karaoke or stuff like that, where the subtitles change all the
time.

-- 
Clément B.
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