[Theora] a question about Bitstream Header.

Ralph Giles giles at xiph.org
Mon Nov 1 00:25:02 PST 2004

On Mon, Nov 01, 2004 at 05:17:47PM +0900, Atsuhiko Yamanaka wrote:

> For example, in the implementation, NSBS, NBS, NMBS defined in spec
> are not expected in the header.

Ah. Yes. The table at the beginning of section 6.2 is confusing. It
describes the *Output parameters* of the header decode procedure given
in that section, not the contents of the header itself. NSBS, NBS, and
NMBS are all calculated from other fields that are stored in the 
bitstream header, as indicated by steps 21-23 of that section. 

Other sections of the specification refer to these values, so their 
calculation is specified here. Since the alpha 3 reference decoder 
does not support block-level quantization index switching, it does
not need to calculate these.

Regardless they do not occur in the bitstream header itself.

I hope that clears up the confusion,

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