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Possible Poor Performance Of Alt-presets, found a problem sample?
KikeG
post Sep 23 2002, 23:58
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I've just doing some ABX tests with the sample trumpets1.wav, which you can find at http://www.pcabx.com/product/reference/trumpets1.wav

It's a trumpet sound, with no pre-echo issues, just added harshness on some alt-presets.

My results:

--alt-preset standard: 6/6 p= 1.6%, quite easy
--alt-preset standard -Z : 7/7 p= 0.8%, quite easy
--alt-preset extreme : 7/7 p= 0.8%, quite easy
--alt-preset extreme -Z : 12/14 p= 0.6%, seems more difficult, or I'm more tired
--alt-preset insane: 3 trials, total 20/32 p=14%, quite difficult, I think I can ABX it on optimum conditions, but I can't prove it right now rolleyes.gif . Edit: not so sure I can ABX it...





So, seems that the VBR alt-presets have more room for tuning?
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Dibrom
post Sep 24 2002, 00:57
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There are a few type of samples where there are still some problems with --alt-preset standard, yes. They are not extremely common though.

As for the cause of the problem, that basically resides at the core of nspsytune, noise shaping type 2, and the different quantization comparison methods. There is a whole lot of room for improvement in the core psyacoustics of LAME. Many of these things were going to be addressed in the now defunct nspsytune2 (Naoki Shibata has virtually disappeared from the scene for what I understand to be some personal reasons...). I'm not sure if they'll ever be fixed now. They aren't really things that I have enough knowledge to fix by myself either. The best I can do is try to bypass as many of the existing flaws as possible, and that's pretty much what the --alt-presets already.

In summation, I don't think the --alt-presets are going to get much better without the core psymodel of LAME being massively overhauled first sad.gif

MP3 really isn't the best choice these days if you want the best quality in all (or nearly all) cases. Most of the other newer formats have much better performance and a higher degree of reliability for delivering a set level of quality.

However, I do appreciate your input wink.gif
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