[vorbis-dev] More spec notes

[Monty]

On Fri, Aug 02, 2002 at 05:36:37PM -0400, Kenneth C. Arnold wrote:
> A few more notes on the specs -- I just spent a few minutes and did up
> floor 1 header decode. Short and sweet, but still important.
> 
> Monty, please read these and my several earliers -- I'm trying to
> improve and validate the spec for your codec, and though I understand
> you were taking a break before, a reply would be appreciated. Note
> (again, if you read my other emails) that if you help me get CVS
> access restored, I can make some of the changes myself instead of
> bugging you for everything.
> 
> Another person has already expressed interest in undertaking a similar
> project to mine. For that and other reasons, I'd also like to commit
> what I have so far to CVS.
> 
> Here goes for this round:
> 
> vorbis-spec-floor1.html
> * header decode
> - step 5 - so maximum_class + 1 iterations?

correct 

> - step 9/10 - what to do if subclasses == 0 (or does it matter? I don't think so)

Ah, what do you know.  Spec bug, but not where you thought:

There's always at least one class if there's at least one partition.
If there's not at least one partition, there are no classes.  So, step
2 should be:

  2) [maximum_class] = -1

> - step 12 - really subtract 1? why not store it minus 1 in the stream?

"Because it isn't" :-)

> - step 22 - the first assignment writes to X_list element j+values = 0+1 = 1,
>   overwriting the previously stored element there -- how big is X_list anyway?

You're right, floor1_values should start at 2 in step 17.

The X_list is calculated from partition classes and order.  If you
have three partitions of class 0 1 and 1, then it would be 2 + size of
class 0 + 2 * size of class 2.  The total size of the list isn;t read
anywhere, it has to be counted.

Monty
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