[theora-dev] dead DCSearchPoints code
dan at on2.com
Tue Jun 17 23:50:20 PDT 2003
> From: Mike Melanson [mailto:melanson at pcisys.net]
> BTW, do you have anything to state about that discrepancy/bug I
> found awhile back related to macroblock decoding? I plan to
> write it up as
> a bug in the original implementation.
Just today, I finally got through the joy that is superblocking. I am now onto the even greater joy of DC prediction (yuk!), with excellent help from your document (note a slight mistake -- left column (group 1) can only use U & UR predictors, not UL)
BTW I think I will scrap the group numbering as it's really an implementation detail, and rather confusing. Once you get through the smoke, it's actually not *too* complex. The implementation details make it seem worse than it is (I think -- haven't really got it working yet).
Also, sanity check -- DCSearchPointCount is always zero, so the code that looks through the DC search points never gets called, right? It falls through to Last[WhichFrame], ie last block coded, or zero if no blocks coded...? Nice if true, less craziness to document.
As for that possible bug, I have a vague memory of one of the original VP3 programmers explaining something once about how the color modes are tied to the Y modes, so I suspect it's not really a bug... but this could be a bad dream... in any case, if it were a bug, I think things would be way screwed up & we would have noticed. More likely it's just another of the cruelly subtle coding that makes VP3 analysis such a challenging hobby...
Thanks much for the contribution! Sure you don't wanna do IRC? Great timewaster, but we sometimes actually talk about this stuff ;*}
___ Dan Miller
(++,) Founder, On2 Technologies
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