[FFmpeg-devel] YUV to RGB conversion, optimized ARM assembler code

[Frank Barchard]

On Sat, Aug 8, 2009 at 1:18 PM, Yonas . <googelly.eyes at gmail.com> wrote:

> M?ns,
>
> Have you looked at the code yet?
>
> Yonas


My ARM is rusty, but I can comment on the algorithm.
The table look up method avoids multiplies and is the fastest way.
The tables are preclamped, you loose a little quality.  If you use
saturating adds (qadd16
instead of
sadd16) you can unclamp the tables... allow the values to go from 0 to 0xff.
 Otherwise you cant get full black and white.

Its doing 2 rows at a time.  You may improve performance doing one row at a
time.  x86 does better one row at a time, despite the duplicated UV math.

You can simplify the code by doing just the horizontal loop in ARM and the
outer Y look in C, without loosing much performance.  Then it can apply to
422 as well.

ffmpeg uses swscaler for conversion.  This wont drop in easily, but it is
faster.