Hi Frank!
Frank Klemm schrieb am Sam, 05 Aug 2000:
> ::
> :: Sorry, I don't get your point here, what is FS?
> ::
> FS = Full Scale = maximum SPL possible for a sine wave.
> Average Level is usually 10...14 dB below FS for modern music.
OK
> For any ATH calculation you must assign FS a SPL (Sound Pressure Level).
our adjustment for the ATH is 114 dB.
(see ATH formula in util.c, adjustment in quantize-pvt.c)
> The ATH is different for different assignments, so the bit assignment
> depends on this assignment.
I think here is a point of misunderstanding. In Layer3 we don't have a bit
assignment loop, but a noise allocation loop.
For CBR encoding we assign a fixed base amount of bits depending on the desired
bitrate and some additional bits from the bitreservoir depending on the
perceptual entropy, some output from our psymodel.
The next thing to do is allocate noise from scalefactor bands which can carry
more noise so that the distortion in other bands gets lowered (scalefactor
colouring) and to control the injected noise (quantizer stepsize). Hopefully,
in the end all bands have a distortion less our thresholds, but, in case of too
few bits, distorted bands will remain.
So, if you vary the ATH adjustment, you vary the amount of noise which can be
allocated, but only if the ATH is over our masking thresholds from our
psychoacoustic model.
> --
> Mit freundlichen Grüßen
> Frank Klemm
>
> eMail | [EMAIL PROTECTED] home: [EMAIL PROTECTED]
> phone | +49 (3641) 64-2721 home: +49 (3641) 390545
> sMail | R.-Breitscheid-Str. 43, 07747 Jena, Germany
Ciao Robert
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