[theora-dev] VP3 IDCT

Dan Miller dan at on2.com
Thu Mar 6 12:14:08 PST 2003

> > The DCT/IDCT in VP3 is 100% integer-based, so our 
> philosophy is: you must
> > duplicate it exactly.  Drift is not allowed.  Therefore maximum frames to a

> that means that existing IDCT hardware cant be used :(
> and neither existing software IDCTs :(

perhaps -- it depends on the hardware.  Most of my experience lately has been with firmware-programmable DSP engines that are more than flexible enough to deal with various definitions of DCT.  I don't think you're likely to see Theora get hammered into a completely inflexible ASIC anytime soon, and if it is, it can be designed according to the spec for the same price as existing similar-complexity algorithms.  Note that H.264 has a similar philosophy now with their 'DCT-like' integer transforms.

Look, someone can go ahead and create a non-spec decoder that might look OK, but I think we should discourage it.
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