剛看到的文章

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

上面講的概念大部分都對，不過要注意的是內容講的是MP3的壓縮
所以上面講的Bitrate並不適用於Mpeg 1 layer 2

另外，有些MP3 Encoder（例如LAME）在壓縮MP3的時候如果選擇Joint Stereo的話，會視需要從Mid-Side(MS)與Stereo之間切換以增進壓縮品質，如果是這種情況的話，就應該可以安心使用Joint Stereo了

可是TMPGEnc有內建這種功能嗎？而且Mpeg1 Layer 2允許這種中途切換模式嗎？又產生了新的問題。