Vorbis development, status & patent issues, PART 2 - Technical discussion Options

[Gabriel]

Moderator comment
Currently the Vorbis patent issue covers these threads:
Vorbis development, status & patent issues PART 1 - NON-technical discussion
Vorbis development, status & patent issues PART 2 - Technical discussion (This thread)
/Moderator comment

By looking at this:
http://www.xiph.org/archives/vorbis-dev/20...2/index.html#83
it seems that Xiph (at least in 2000) was open to the idea of disclosing the patent research.
Is this position changed now, or does it still stand?

[Ivan Dimkovic]

I took a deeper look at the patent - It seems that this patent does not talk about switching criteria at all - they just state 'signal amplitude change' as a condition for switching to the short blocks, which is met in every codec, regardless of the actual switching method - otherwise there would be no point in window switching at all (if energy level is the same).

On page 6 they suggest that signal amplitude change of a given magnitude could be used as a trigger - but they do not state whether this is in time or freq domain - it can be both.

Window switching criteria can be either time-domain energy diff, freq domain energy diff (vorbis is using this, right?), perceptual entropy change (like MP3/AAC) or LPC predction error (Twin VQ, for example) - but I think MP3 and AAC and TwinVQ reference this patent as relevant, and it is in patent portfolio, and they do not use strict "signal amplitude change" in time domain as someone would initially think. No matter how the blocks are compared (time E, freq E, PE (THR/E), or LPC prediction error), window switch is always a result of signal amplitude change IMHO.

This post has been edited by Ivan Dimkovic: Sep 26 2003, 01:08