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Subject: Re: AW: Question about CD-Quality and MP3

Re: AW: Question about CD-Quality and MP3

From: Frej Bjon <>
Date: Thu, 02 Feb 2006 17:22:02 +0200

On Thu, 02 Feb 2006 16:37:29 +0200, Michael E. DiFebbo <>

> This is a common misperception, but at best it is only partially true.
> The term "joint stereo" has two different meanings when used with
> respect to encoding MP3s.
> The joint stereo method that you refer to is "intensity stereo."
> Intensity stereo is only used by modern MP3 encoders for very low
> bitrate files (lower than 96kbps if I remember correctly). For higher
> bitrates, "joint stereo" refers to M/S stereo.

Ah, how wonderfully unambiguous. Well, in that case, it used to be that
you should use stereo encoding, but these days the encoders are smarter
than that :).

Now that you mention it, I do recall that encoders can decide
frame-by-frame which method to use (M/S or separate channels), but I
wonder how it's decided which is better. Encoding with both and picking
the one with smaller size is trivial, but inefficient. Also, you say M/S
is more efficient to encode when much of the source is centered and mono,
but does the opposite apply? Is it less efficient if the stereo field is
really wide?

Received on 2006-02-02

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