[vorbis-dev] vorbis on playstation 2

[Nicolas Pitre]

On Thu, 6 Feb 2003, David Etherton wrote:

> > > 44% mdct_backward
> > > 10% _vorbis_apply_window
> > > 9% vorbis_book_decodevv_add
> >
> > This is obviously cache kill.  Note that the mdct itself is not the
> > only culprit of that, of course.
> 
> Interesting.  I turned on _LOW_ACCURACY_ and rebuilt the library and the
> total cycle count for my test case went from 950M cycles to 723M cycles.
> The two sincos lookup tables are 4K each in "full" mode which are likely
> going to thrash the cache.

Depending on the stream used, the second table is unlikely to be referenced.

> I could move the whole LUT into scratchpad easily enough (some of our
> low-precision character animation uses a small lut in scratchpad already, it
> was a pretty good win) although I'd like to trim the table down a bit.
> Would I be better off going to a signed short to cut the table size in half
> or just cut the number of entries in half?

If you used _LOW_ACCURACY_ the sincos tables were compiled as unsigned char 
automatically.

<p>Nicolas

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