[vorbis] fake stereo

[Christian.Buchner]

> I think all audio CDs are two-channel, aren't they? So mono recordings
> would have to be done as two identical channels (nobody could be so dense
> as to release it as left-channel-only, with the right channel silent, and
> surely no one is still promoting "mono reprocessed for stereo", that
> vile atrocity of the '60s and '70s?). Certainly in my experience, when I
> rip a mono CD, I get two channels 

The situation gets even worse when the Mono recording has been processed
with analog equipment and then burnt to a CD  (AAD).  The left vs. right
audio levels will vary and you have uncorrelated noise on both channels.
Even though the original recording is Mono.

For an example of these types of "Mono" files, go to http://sound.media.mit.edu/mpeg4/audio/sqam/

The male/female speech samples (SQAM samples by the EBU) are a good example
of this problem. Sure a challenge for lossless audio coders. Try adding the
inverted right channel to the left channel, e.g. with GoldWave and you will
notice a residue signal.

A good audio coder should be able to exploit the correlations to the extent
possible.

With regards,

Christian Buchner

--- >8 ----
List archives:  http://www.xiph.org/archives/
Ogg project homepage: http://www.xiph.org/ogg/
To unsubscribe from this list, send a message to 'vorbis-request at xiph.org'
containing only the word 'unsubscribe' in the body.  No subject is needed.
Unsubscribe messages sent to the list will be ignored/filtered.