[mythtv-users] MythTV & Dolby ProLogic question

[Cliff Draper]

From: "Rasmus Ekman" <rasmus.ekman at kryddsill.net>
Date: Wed, 12 Feb 2003 04:51:00 +0900
> those not familiar with join-stereo, it compares the difference between the
> two channels and thus mannages to have a higher quality/filesize ratio.
> Encoders used to be kind of bad at doing this, and so it got a bad rep.
> However, nowadays lame does a terrific job.

Joint stereo is great for 2 channel sound sources, as the compressed
stream is based off of both channels, compressing out little
differences.  And it is exactly those little differences where Dolby
ProLogic stuffs it's extra info.

http://www.digvid.info/tmpgenc/beginners.php:
"Joint-stereo: This makes low frequency bands mono, and high frequency
bands stereo. The human ear is more sensitive to the direction of high
frequency sounds. Note that this setting destroys Dolby Prologic
information, so if you source contains Dolby Prologic information
choose Stereo mode instead."

>From http://lame.sourceforge.net/USAGE:

"jstereo means the encoder can use (on a frame by frame bases) either
regular stereo (just encode left and right channels independently) or
mid/side stereo.  In mid/side stereo, the mid (L+R) and side (L-R)
channels are encoded, and more bits are allocated to the mid channel
than the side channel.  This will effectively increase the bandwidth
if the signal does not have too much stereo separation.

Mid/side stereo is basically a trick to increase bandwidth.  At 128 kbps,
it is clearly worth while.  At higher bitrates it is less useful."

Cliff Draper    Sun Microsystems, Forte Tools
My opinions may or may not reflect those of my employer.
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