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Alt-Preset Standard/Extreme Flaimbait
idfubar
post Apr 30 2003, 18:53
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Forgive me, but a quick question:

Is there any way to determine the difference between alt-preset standard/extreme settings mathematically?

The reason I ask is a CD is limited to a Signal-To-Noise Ratio of 96. Since the limiting factor in encoding is the fidelity of the source, is there someway to determine a "threshold" where using extreme v/s standard can be shown to be advantageous (i.e. shown to have an audible resolution) mathematically?
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Gabriel
post May 1 2003, 13:38
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SNR is not relevant for a lossy codec using psychoacoustics.
In a lossy codec not using psychoacoustic properties, like a dpcm codec, it might be relevant.

Back to mp3.
SNR is not relevant, because the job of the codec is to use at any moment the lowest SNR ratio for a given frequency band, without beeing noticable by a human ear. The lowest the SNR, the more bits are saved.

There is no higher theorical limit to the SNR ratio of mp3 neither, because it is using as many bits as needed (determined by the psychoacoustic model), so it is not limited to 16, 24 or even 32 bits. It has an unlimited resolution.

I know that several "hi-fi" magazines tryed to measure the SNR value of mp3. This is just an indication that they do not understand the underlying technology. (no pun intended, everyone has his own knowledge field)

The dynamic range of the codec can however be mesured. For Lame it should be around 110-120 dB.
If I remember well, someone here measured it in the past.
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