Mark Taylor wrote:
> I finally got a chance to thoroughly read Davis Pan's articles. Some
> questions for the experts out there:
>
> For Layer 3, why bother with the "polyphase" filterbanks? Why can't
> you process the whole frame with a single MDCT - then start removing
> and quantizing the MDCT spectral coefficients based on the psy model?
>
The MPEG1layer3 use the same structure as the previous layer ( subband filter..) and
add new more performance �tools� (as the MDCT transformation..).The subband filter is
used when we will quantize the �time� samples, divided in different frequency groups:
in effect the new compression algorithm �AAC� (MPEG2 NBC/MPEG4) use only the MDCT
transformation without subband filtering.
> Pan talks about several components of the psychoacoustic model:
> ...
>
> 3. tonal/atonal components: This is only alluded too. The different
> components have different masking properties. Anyone know what
> this is? I'm guessing the tone-masking-noise is stronger than the
> noise-masking-tone?
> ....
>
>
> Mark
There are four different cases of masking paradigms:
1. Noise-masking-tone,
2. Tone-masking-tone,
3. Noise-masking-noise
4. Tone-masking-noise.
In our case, the maskee (the element masked by another element, �the masker�) is the
quantization noise: so we are interessed only in the 3. And 4. Case.
The problem is that this two cases have received little attention in psychoacoustic
research, due to the difficult of such measurement.
The following observations (with the results from the first two cases measurement)
help us to determine the offset:
The noise is a better masker than a tone and a tone is an easier maskee than noise.
Davide
