What fraction of work is iDCT?

Jeffrey W. Baker jwbaker at acm.org
Mon Jun 25 18:57:40 CEST 2001

On Mon, 25 Jun 2001, Eugenio Jarosiewicz wrote:

> (Jeff: I'm cc'ing you as I don't know if you're on the list)
> Ok, so someone else who knows more about this than me already gave you
> some #'s.  But of quite interest might be:
> Altivec IDCT sample plus much more...
> http://developer.apple.com/hardware/ve/examples.html
> http://developer.apple.com/hardware/ve/
> ( I wish I had done a more completesearch earlier )
> Jeff - have you taken a look this?  I'm very interested about getting
> this into VLC for OSX and ppc in general.  I don't know much about
> vector processing but the concept seems fairly straightforward.

These are the routines I have plugged into VLC.  I am having a problem
though that keeps me from testing it.  When I start VLC, it simply reads
the blocks off the DVD as quickly as it can, without playing any video.  I
haven't had a chance to debug this problem, and I think it is unrelated to
the vectorized IDCT.  It may be related to the new firmware Apple
downloaded ont my DVD-ROM, but Xine still works OK.

Still, nobody told me wether 377,000 IDCT iterations per second is fast or


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