[vorbis] joint stereo - advantages / when?

[Aleksandar Dovnikovic]

Monty <xiphmont at xiph.org> wrote:

> The problem with joint stereo is that the perceptual qualities of the
> two encodings can sound very different, and if the selection algorithm
> makes a mistake...
> It may also be the case that you also may not notice a quality
> difference between the two modes (L/R or mid-side), but you would
> notice the transition from one mode to the other.
> 
> Because the selection algorithm is not perfect, at higher bitrates,
> LAME turns joint stereo off by default.

As far as I am into the technical side of joint-stereo, joint-stereo
implemented in Vorbis will be different then MP3. MP3 j-stereo
algorithm determines whether M/S or L/R will be used on a
frame-by-frame basis, while Vorbis does that but not for the
whole frame - it is focused on frequency regions... ?
That is why it's not an easy job...

> b3 will not have it (yes, it's somewhat more difficult than other
> features).  b4 *will* have it.

What will be the main differences between b2 and b3?
B3 coming out soon?

Greetings,
Aleksandar

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