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Topic: Vorbis -q6: Doubts between joint stereo and lossless stereo (Read 8528 times) previous topic - next topic
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Vorbis -q6: Doubts between joint stereo and lossless stereo

I've read about the differences on the encoding strategies of joint-stereo and true-stereo, and -q6.0 seems to be the start point for the use of lossless stereo. So I suppose that -q5.9 (or 5.99 ) will be joint stereo. Quality 6.0 is more than good for me, but the ask is:
Is there any advantage selecting -q5.99 instead of 6.0?
Thanks and regards.

Vorbis -q6: Doubts between joint stereo and lossless stereo

Reply #1 –
The advantage will be a slight bitrate reduction.

Vorbis -q6: Doubts between joint stereo and lossless stereo

Reply #2 –
Joint Stereo is lossless stereo.

Vorbis -q6: Doubts between joint stereo and lossless stereo

Reply #3 –
Joint Stereo is an MP3 mode that allows the encoder to toggle between Mid-Side stereo and Left-Right stereo coding on a frame-by-frame basis.

It is pointless and does not exist in any more modern codec like Vorbis or AAC, which have the ability to toggle the most efficient coding method per frequency band. Neither Vorbis nor AAC use Joint Stereo at any bitrate.

Both Mid/Side and Left/Right stereo are "lossless" in that they do not lose any stereo information by themselves.

Vorbis -q6: Doubts between joint stereo and lossless stereo

Reply #4 –
I think he wants to know the difference between channel coupling point vs. lossless in Vorbis...

Vorbis -q6: Doubts between joint stereo and lossless stereo

Reply #6 –
Thanks for the answers and sorry for the confusion. It was due to my bad english plus this:
Quote
Channel coupling is a method used to reduce bitrate demand by coding the stereo channel information more efficiently. There are several channel coupling methods. In MP3 the general term is joint stereo.

And this:
Quote
Lossless coupling is equivalent to independent encoding of the two channels ('dual stereo' in MP3), but with the benefit of additional space-saving. It does polar mapping/channel interleaving using the residue vectors.
In point stereo, the stereo phase is discarded completely. All the stereo information comes from the difference in the spectral floors for the left and right channels.
Ogg Vorbis uses lossless/point stereo coupling below -q 6. Lossless channel coupling is used for high bitrates entirely (-q 6 and up).


Then I understand that Vorbis always uses some kind of channel coupling. But maybe Vorbis "could" be more efficient using point stereo at 5.99 instead of lossless stereo at 6.0. Or maybe this is an example of one of those pointless tricks, and 6.0 is always better than 5.99.

Vorbis -q6: Doubts between joint stereo and lossless stereo

Reply #7 –
I'm actually still confused about the concept. If coupling is supposed to be "more efficient" than the lossless method by introducing lossy methods and approximations (as far as I can see, at least), why is the lossless method largely preferred?

Is it just on the merit that it is lossless?

(No sarcasm, please. I am asking this question sincerely. )
 

Vorbis -q6: Doubts between joint stereo and lossless stereo

Reply #8 –
Quote from: Zarggg on
If coupling is supposed to be "more efficient" than the lossless method by introducing lossy methods and approximations (as far as I can see, at least), why is the lossless method largely preferred?


There's nothing as "absolute efficiency". In other words, efficiency is always relative to something (either previous or new).

In this context  lossy coupling is more efficient in the use of bits than lossless coupling, as it uses different techniques which reduce the need of bits in order to reach a similar objective (in this case, stereo (or more channels) imaging).
The technique, though, when pushed to its limits, makes the signal almost monophonic, (in effect, reducing almost the usage of bits for this concrete task).

As such, the codec increases the use of the feature, as less bits (lower quality) is asked by the user. If the tuning is good enough can just be found out via listening tests or heard with killer samples (two different sounds playing one on each channel could be one).

Quote from: AngelGR on
But maybe Vorbis "could" be more efficient using point stereo at 5.99 instead of lossless stereo at 6.0. Or maybe this is an example of one of those pointless tricks, and 6.0 is always better than 5.99.


5.99 cannot be better than 6.0 in respect of the audio imaging, just the same. If 5.99 is tweaked in such a way that the bitrate jump is linear, and lossy coupling represents a jump in bitrate at its max quality compared to lossless coupling, then, the stream could have a higher quality.

I haven't done tests in order to prove or disprove that, and i'm not sure it would be easy to do.