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LAME's resampling leaves something to be desired
eamon123
post Oct 15 2012, 20:16
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http://shibatch.sourceforge.net/ is a good resampler. It beats lame in quality every time. Here is an example:

Yes I retested Baba O'Reilly and it sounded noticibly better with ssrc.

I did

FLAC 88.2 > lame.exe -S --noreplaygain -b 32 --lowpass 10 --resample 24 - %d
VS
FLAC 88.2 > WAV > ssrc.exe --rate 24000 --bits 16 > lame.exe -S --noreplaygain -b 32 --lowpass 10 - %d

in ABX and got 14/16 (0.2% prob of guessing). I was hearing a whole different type of artifact that I have either never heard before or just never listened for before. I was 5/2 up when I started listening to the bass drum and it just sounded fuller, warmer and louder in ssrc. It was then that I noticed that there was a shrill artifact at about 9 kHz at the same time as the drum beat in question. It was obvious in both files, but louder in the LAME version. Up until now the bass drum "masked" it, "masking" is seriously like an aural illusion, that bass drum sounded fine before I heard the shrill in one and then I heard it in the other, I was dumbfounded! After that I just listened for that beep and the louder one was LAME. LAME should really look into their resampler, a lot of people are downsamping high res FLACs these days!

I feel like I did the first time I discovered that I had a blind spot on my retina that I could "discover" at will with carefully engineered designs and some ordinated displacement of said designs. Discovering the nature of my aural blind spots first hand I can only describe myself as feeling enlightened!

Maybe that shrill noise is due to a crappy lpf in LAME?

https://rapidshare.com/files/1612342437/ssrc.vs.lame.zip





ssrc is foss, maybe the LAME devs would like to copy some of it's code?
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pdq
post Oct 16 2012, 15:36
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Since the differences seem to be localized to frequencies very close to fs/2, and since this is followed by perceptual encoding, isn't it possible that what you are seeing is not necessarily due to differences in the quality of resampling?

IOW, something innocuous like the steepness of the cutoff could allow or not allow frequencies that cause encoding problems to be present, and this causes artifacts in one that are not present or significantly reduced in the other.

What I am saying is that the perceptual encoding step could completely invalidate a comparison of the quality of resampling (though I don't see any other way to test the resampling algorithm in lame).
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