[theora-dev] dead DCSearchPoints code

Dan Miller 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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