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Q : What's the difference between the various stereo modes?
A : It's important to understand the difference between Stereo and Joint Stereo.
'Joint Stereo' modes take advantage of the similarities between the L+R
channels. This allows more bits to be used in other areas and in many cases
this can give an overall gain in encoding quality. Almost all encoders use
joint stereo when encoding at 128 kbits.

Joint stereo has 2 submodes called IS and MS. 'Joint Stereo IS' destroys
phase information and shouldnt be used for high-quality encoding.
'Joint Stereo MS' means Middle/Side and is OK for use in most encoding.

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.

In summary, for most audio, Joint Stereo MS at 128 or 160 kbits should be
fine. If your audio is especially 'wide' and creates flange you should use
'Stereo' mode. You can change these modes in the Radium codec control pan