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-   -   psy.c: CalculateSMR ? (https://forum.musepack.net/showthread.php?t=364)

andym00 13 May 2007 09:07 am

psy.c: CalculateSMR ?
 
Just curious, but I've been following Musepack since it's original invocation, especially it's psychoacoustics and have always been a massive fan its results, and I've just noticed that the signal to mask ratio calculations have changed (significantly) since I last looked at it..

Can one of the developers explain to me why during signal to mask ratio calculations that the peak SMR discovered in a FFT resolution thresholds when find for each subband are now scaled by 1.44121959671885364405f ?
Previously, as far as I can see, it never used to inflate the SMRs like that, merely scaling by 0.0625f and which this additional scaling the bitrates seem overinflated.. Over inflated for a given NMT & TMN.. Maybe as much as 20%-30% increase in final bitrates..

Has in previous previous incarnations the psychoacoustics been miscalculated ? Or am I missing something here ?

I can't actually see when this change was made, but am very curious about it..

Lefungus 13 May 2007 08:06 pm

Can you post more details ?
I only see that in psy.c:835 which seems to contradict what you're saying.
Code:

        *smr0++ = 0.0625f * *erg0++ / tmp0;
In any case, that code was like that in the first public tarball of mppenc code from Klemm

andym00 14 May 2007 11:00 am

Ahh, okay, I see now..
In SVN it's as its always been, but in the musepack-1.95z67.zip I was looking at it's changed..


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