Ah okay, knew there was a reason. Guess I missed the parts in your blog where you mentioned you were looking into it.

I did a bit of searching, looks like there was plans during Google's Summer of Code 2007 to add see2 and altivec into libtheora. But I haven't found anything from that.

I did however find this in FFmpeg's mailing list:

16% faster theora decode on a G4.

Click to expand...

[FFmpeg-devel] [PATCH] Altivec VP3 IDCT

http://gitorious.org/~astrange/ffmpeg/ffmpeg-mt/blobs/master/libavcodec/ppc/vp3dsp_altivec.c

But it's part of the Libav library so I don't know if it's possible to implement this.

There appears to be Altivec YCbCr->RGB conversion in the liboggplay library: http://git.xiph.org/?p=liboggplay.git;a=commitdiff;h=1228bebc7f21f0b6c7014b475c96e792fee2a362

But it's commented out:

//altivec intristics only working with -maltivec gcc flag, //but we want runtime altivec detection, hence this has to be

//fixed!

//#include "oggplay_yuv2rgb_altivec.c"

Click to expand...

Looks like it would take a bit of scissors and glue. That is if anything I found is useful. Oh well. I'm in no hurry, even if it never gets built into the browser, I can always download and then watch it. And yeah, Webm is looking pretty good. Although at this moment Theora still plays smoother on my PowerBook G4. (at least, out of browser it does, need to do a comparison within TFF.)