Re: Video Coding Puzzle

On Fri, 9 Jul 2004, Jim Leonard wrote:

> > We are hoping to form a clearer expression of some of the decoding
> > algorithms before releasing the source code. What follows is a description
> > of a peculiar function that almost seems to have some DCT-like properties.
>
> Maybe it's a block slant transform?  (Similar to DCT but much faster math)

	I considered that, especially since the transform appears to
propagate values down the diagonal of the block. But I don't know enough
about slant transforms to rule on that.

> On a side note:  Unless my memory is playing tricks on me, I recall playing WC3
> on an AMD 386/40MHz and the video played fine too, occaisionally stuttering
> because my CDROM drive at the time was only 1X (150K/s) while the datarate of
> the WC3 video required up to 180K/s at points.  If it wasn't my 386/40 then
> maybe it was my 486/66 that I upgraded to a year later... but in both cases WC3
> didn't require a Pentium to decode the video.

	WC3 video does not take much computing power at all to decode,
with its RLE, textbook Huffman coding, and run-based motion compensation.
No multiplications anywhere to be seen. In fact, it ran fine on my 486DX2/
66 MHz machine. As for datarate, the audio took up 1/4 of a 1X datarate
(audio samples were 16-bit, but 22 KHz vs. 44 KHz for CD-quality, and mono
vs. stereo).

--
	-Mike Melanson


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