It seems that parametric stereo is beeing silently added to the MP3Pro extensions under the name "Low-Complexity Stereo":
http://mp3licensing.com/mp3/mp3pro2.html

This is not really true

LC stereo is implemented for ages in mp3Pro (check Nero and I think it is not related with parametric stereo.

I am no expert in mp3Pro, but I think LC stereo is equivalent of SBR coupled channel mode (in MPEG-4 doc) - which is indeed more effective than normal stereo, but still far from "real" parametric stereo extensions introduced few months ago.

Never noticed it. Perhaps I should update my Nero version...


In sbr coupled channel, what is coupled? Only the sbr part, or the whole spectrum. In the mp3pro case, it seems that the whole spectrum is coupled.

Hmm - LC stereo could be found in expert options in Nero mp3Pro codec, and I am quite confident that it was present for a long time, much before the ideas behind PS emerged.

In coupled SBR, only the SBR part is coupled - but, perhaps Menno knows more - in earlier DRM (digital radio mondial) versions, there was some kind of LC-stereo mode IIRC, which did some simple downmixing and re-generating of the stereo image in the decoder - it was much simplier than current parametric stereo.

So... what's the difference between LC stereo and parametric stereo ?

They both seem to produce a mono stream for backwards compatibility and some "parameters" of how to get a stereo version of it for decoders capable ot handling LC stereo / parametric stereo.

I don't know for sure, but I guess these "parameters" are in both cases some kind of frequency varying panning positions, right ?



Any (public) papers available ?


bye,
Sebi

Does the current DRM have parametric stereo?

LC stereo is a tool comparable to PS in the fact that it converts mono to stereo (or attempts to do that).
LC Stereo is a set of simple filters, that can only be turned on or off in the bitstream. PS on the other hand can be carefully controlled by bitstream parameters.
LC stereo works in the time domain, PS in subband domain.

DRM used to have LC Stereo, but in the latest versions of the standard DRM uses PS (but not the same as MPEG-4 PS)

Edit: for the interested people: http://www.audiocoding.com/lc_stereo.m
There is 1 control parameter BTW, lc_stereo_mode, it can have 3 different values.
Oh yeah: this Matlab script sounds crappy because it doesn't save the filter states between frames, thus you'll hear cracking sounds on frame boundaries.

Menno