[vorbis-dev] vorbis on playstation 2

[Nicolas Pitre]

On Wed, 5 Feb 2003, Brad BARCLAY wrote:

> 	The "ogg123" process, as compiled for the PS2 Linux kit, in
> testing took about 90% of the core MIPs processors processing time --
> so the direct recompile is hardly lightweight.  Obviously, using the
> vector units will present a major performence enhancement opportunity.
> 
> 	Of that ~90%, 14% was being used by _fpadd_parts.  Alot of time
> appears to be wasted while doing floating point arithmetic, probably
> due to the fact that Vorbis uses lots of double-precision floats, which
> are emulated on the PS2.
> 
> 	Of the actual Vorbis sources, 12% of the processing time is
> spent in mdct_backward (mdct.c).  the next most used is 9% by
> vorbis_book_decodevv_add (codebook.c), and 4% is used by ov_read
> (vorbisfile.c).  Of these, the first two are probably good cantidates
> to porting to vector assembly.
> 
> 	Cache miss is also fairly high -- nearly 50%.  Again,
> mdct_backward appears to be the biggest culprit.

It would be interesting if you could do the same analysis with Tremor.

I've made many cache improvements in Tremor's mdct_backward some time ago.  
Cache usage clearly improved on an ARM processor compared to the earlier 
version of the same function, but I don't know how it compares to the 
libvorbis version.

<p>Nicolas

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