Jim Lesurf wrote:
In article , DAB sounds worse
than FM wrote:
Jim Lesurf wrote:
In article , DAB sounds worse
than FM wrote:


Because Radios 1 & 2 and all the pop stations have audio processing
applied then the spectrum tends to be wide and flat, which tends to
result in aa lot of remaining frequency components after the
psychoacoustic model has produced the masking curves to throw away
the inaudible subbands.

Is that the case in the timescales relevant for the data reduction
'frames' (or whatever the correct term is)? I can see that R1/2 tend
to use audio 'compression' (in the old sense) and this may work to
flatten the medium term power spectrum. However that does not in
itself mean the spectrum is 'white' if it has a finite number of
components. Nor does it necessarily mean that each individual
processed time-frame will have a near uniform power spectral
density. Do you have some data on this relevant to R1/2?


No data; I've just looked at a lot of spectra. I know it's not white,
but it's a hell of a lot flatter and broader for R1/2 than R3. R3
tends to tail-off quickly, whereas R1/2 tails-off significantly
slower and for the vast majority of the time it goes right the way
up to the brickwall filter.

The difficulty is that doesn't necessarily lead to your conclusion.
The spectral components present in any time frame may extend across a
wider range, and be more unform in size. But if the *number* of
components that are resolved in the time frame are sigificantly less,
then the 'weeding' process may lose less info. Impossible to assess
this without much more specific info than simply observing a tendency
for the components that are present to have similar levels, etc.

Hence I think the point you make is certainly an important one, but
it may not establish the conclusion you draw without more specific
evidence. Not saying you are wrong. Just saying 'dunno', but 'not
proven' simply from what you have said.


An interesting experiment is to encode some CD material into VBR MP3 at
a given quality level. That way the MP3 encoder chooses what bit rate to
use to achieve the given level of quality on a frame-by-frame basis.

If you want to compare results with me then do the following:

* download Lame v3.90.3:

http://www.hydrogenaudio.org/forums/...howtopic=28123

* I use RazorLame as a front-end GUI, which you can find he

http://www.dors.de/razorlame/download.php

* overwrite lame.exe in the RazorLame folder with lame.exe that you
downloaded with Lame v3.90.3 above

* then in Lame Options in RazorLame use the VBR presets on he

http://www.hydrogenaudio.org/forums/...howtopic=28124

--alt-preset standard
--alt-preset- extreme

Do this by going to the Expert tab, entering one of the above into the
Custom options edit box and tick Only use custom options.

Theoretically, the higher the average bit rate the more difficult that
piece of music is to encode to a given level of quality.


--
Steve - www.digitalradiotech.co.uk - Digital Radio News & Info

Find the cheapest Freeview, DAB & MP3 Player Prices:
http://www.digitalradiotech.co.uk/fr..._receivers.htm
http://www.digitalradiotech.co.uk/da...tal_radios.htm
http://www.digitalradiotech.co.uk/mp...rs_1GB-5GB.htm
http://www.digitalradiotech.co.uk/mp...e_capacity.htm