Howdy Gabriel,

> I was naively thinking that determining the right intensity
> position for
> each subband could also be a problem.

No, this value is completely determined by the signal.  It's an expensive
computation, but it's not complicated.

> > BTW, I was wrong about the number of iterations above.  It
> would be 13 or
> 21
> > at maximum, depending on whether the frame is long or short
> block encoded.
>
> I'd think that even "brute force" would be a lot less than 21
> iterations to
> find isl (is limit). The first naive idea would be to test
> from up(sfb21) to
> bottom. At each sfb, test if "shape" of left channel is
> similar to "shape"
> of right one, just with a different scaling. If it's similar,
> then it could
> use is, and continue testing downward.

Hmmm...  I hadn't thought of trying to guess the threshold from the signal.
The idea clearly has merit; after all, that's how mid/side works.  I was
just planning to check post facto, i.e. apply each level of intensity, and
see if it's an improvement or not.  (Which is how Layer-I,II do joint.)

> I'm quite sure you would stop on average way before testing
> even 50% of
> subbands.
> But the real question is how do you determine if left "shape"
> is similar to
> right shape?

Also, the concept of intensity is based on high-frequency signals not
needing stereo information.  You'd probably want to do some research to see
whether similarity of shapes was actually relevant, and, if not, how low in
frequency you can progress before it is.

Does anyone have any good citations on any of this?

Thanks,
Alex


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