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Subject: RE: Quick questions
From: Chris Holt (amiga2k_at_cox.net)
Date: 2003-10-20


On Mon, 20 Oct 2003 19:13:59 +0100, BlueChip wrote:
> hmmm, wish I could remember what searches I typed in - my URL history
> seems to be missing a chunk - yeah, I know that sounds fishy, but it's
> true !:(
>
> anyway www.goo...
>
>
> http://www.geocities.com/altbinariessoundsmusicclassical/vbr-
> encoding.htm#ch11 "Joint Stereo looks for signals that are identical in
> the left and right channel and if it finds any they are encoded as mono"
>
>
> with regard to the post on "you do not lose quality"
> === THIS IS NOT TRUE AT ALL ===
> Whatever you may read from the net - I can personally assure you
> otherwise. And Yes, I HAVE been put through the "blind test" procedure
> by two of my friends now. But if you need someone with a cool web site
> to say it: http://www.mediatwins.com/FAQ/mp3_stereo_modes.htm
> "However, for some audio, Joint Stereo MS may create a 'flanging' or
> 'swishing' effect. In these cases it's better to use 'Stereo mode'.
> This mode creates 2 independent channels for both left and right. When
> stereo mode is used, you should also use a higher bitrate (160 or 192
> kbits) - Stereo mode will allocate about half of this bitrate for each
> channel."
>
>
> http://www.mp3machine.com/discussion/messages/780.shtml
> quotes William Schelter, Nils Faerber, Alexander Leidinger, Oct 13,
> 2001: "Using mid/side stereo [MS] inappropriately can result in audible
> compression artifacts. Too much switching between mid/side and regular
> stereo can also sound bad." ...which was given as a definition of Joint
> Stereo
>
>
> http://www.iis.fraunhofer.de/amm/techinf/layer3/
> "Joint stereo coding takes advantage of the fact that both channels of
> a stereo channel pair contain far the same information. These
> stereophonic irrelevancies and redundancies are exploited to reduce the
> total bitrate." ...whatever that means
>
>
> I cannot find defitions that agree with ANYTHING I have read so far,
> including my own post!!! What is so illusive about mode?
> Do LAME have an "official" support forum? That may be the place to get
> an accurate answer!?
>
> BC

hydrogen audio has lots of info about LAME and plenty of descriptive
information about LAME's implementation of JS. You can find links in the
FAQ that will make the search easier.

http://www.hydrogenaudio.org/

Go to the FAQ and look for "Why is joint stereo better than pure stereo ?"
It's under the MP3 heading

But! This tells us nothing about the MAS chip and the techniques it uses,
whether they are properly implemented etc.

>From my reading on the subject, I think it is safe to say that you are not
likely to get artifacts, swishing or whatever using LAME JS. I cannot
speak to other encoders, including the one in the Archos.

It dosen't do us a whole lot of good to pursue the issues with LAME JS,
does it?

Chris



Page was last modified "Jan 10 2012" The Rockbox Crew
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