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Topic: determination of M/S stereo (Read 1899 times) previous topic - next topic
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determination of M/S stereo

In lame code

How does it determine whether to use M/S stereo or not?

I read a paper about the determing method.

1. Perceptual Entropy Calcualtion M/S & L/R
2. comparison M/S PE with L/R PE

Is it right?

I think it needs many calculations (about 2 times) whether to use M/S or not.

Does Lame code use this method?

If there is other method, please tell me.

thank you.

determination of M/S stereo

Reply #1 –
Well, whatever it does, it does very well.
 

determination of M/S stereo

Reply #2 –
LAME uses combined method for determining MS or LR coding type:

1. Masking threshold ratio between L and R channels (if it is bigger than, say 5 dB, MS is not used)

2. L/R and M/S  PE comparison of the frames flagged as "M/S" by 1.  to determine final estimated bit demand - mode which requires less bits is used.

Of course, this is rather coarse description - in MP3 you also must take care not to allow constant toggling of LR/MS frames (LR - MS - LR - MS, etc..)  because this generates some unwanted distortions.  Also threshold values could vary depending on the bit demand or coding mode (bit rate) , etc..