[vorbis-dev] vorbis on playstation 2

[Brad BARCLAY]

On Wed, 5 Feb 2003 15:40:12 -0800, David Etherton wrote:

Hey David:

>I'm all for that.  I'm considering Vorbis because I haven't been able to get
>a straight answer on patent royalties for MP3 use in games (it's supposed to
>be relatively cheap but my emails aren't being returned).  Also, vorbis
>claims to be less computationally intensive than MP3, and there are never
>many cycles to spare on the PS2.

        Okay, I've sent an e-mail off to the other official PS2
developer to ensure they're likewise interested.  When I hear from them
(actually two people working for one company), I'll let you know.  I'm
hoping they'll also be willing to collaborate on this, so both teams
don't have to re-invent the same wheel.

        I have found my printed records -- I'm looking to see if I
still have digital copies lying around.  In brief, however, here were
my findings:

        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.

        HTH!

Brad BARCLAY

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E-Mail:  yaztromo at acm.org  Web:  http://www.jsyncmanager.org

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