huge difference between low-pass 20.1 and 20.2kHz

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huge difference between low-pass 20.1 and 20.2kHz

Mike F
Hi,

I did several tests recently with a few audio samples ( mostly created by sox ) - the one I would like to talk about is a 19.3kHz tone @ 48kHz.
when I apply a 20.1kHz or lower low-pass filter, there is a ton of "noise" is the resulting mp3, if I do the same with 20.2kHz low-pass or higher, it is >>much closer<< to the original.
I used 'baudline' and "my ears" to compare the results.

This case applies to Lame 3.99.5 and 3.98 - did not perform any tests on other Lame releases. ( compared to number of vorbis, aac, flac encoding results without a single case that matched or was similar to Lame )


Lame opts used:

lame -V0 --lowpass 20.1 output.wav out_v0_lp20.1_99lame.mp3
lame -V0 --lowpass 20.2 output.wav out_v0_lp20.2_99lame.mp3

http://www.mediafire.com/download/m0c6kjk7svkth7d/sample.sox.48khz.19.3khz.wav

http://www.mediafire.com/download/r8ksklm74css9sy/out_v0_lp20.1_99lame.mp3
http://www.mediafire.com/download/dyanulb8gm9zdq0/out_v0_lp20.2_99lame.mp3


I posted also a thread at hydrogenaudio while waiting for authorization to post on this mailing list:

http://www.hydrogenaudio.org/forums/index.php?showtopic=102229

Thanks!

Mike
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