Andre Yew wrote:

Randy Yates wrote in message ...

This is the problem with these outrageous sample rates. Why do we
need to process at a rate in which over 50 percent of the available
bandwidth is unused?


I think there are valid reasons to process at high sample rates:

1. There's some software out there now (DVD-A) that delivers content
at high sampling rates, and decimating it to lower rates seems to
defeat the purpose of having such high-sample-rate content in the
first place (assuming such high sample rate content is audibly
different due in part to their high sampling rate).

Yeah, that's a big assumption. Why not sample at 4 GHz, ASSUMING
there is content that would make an audible difference?

For the really
optimistic, some day there may even be a standardized hi-res digital
interconnection which may pass along hi-res data unaltered.

So it can be thrown away by the time it reaches the listener's brain?

2. There're DSP operations which require high sampling rates, such as
non-linear algorithms like compression, because non-linear algorithms
generate harmonics which may alias.

You mean like an algorithm I designed into our (Sony Ericsson's)
mobiles?

One could argue that such
algorithms should upsample, do their non-linear processing, and then
downsample,

Not if you want to waste processing power needlessly performing
operations that will have no audible effect.

but for the sake of fidelity through simplicity,

Ahh yes - fidelity through simplicity...

it may be
easier to implement a good-sounding system if the digital processing
were kept to a minimum.

Not if you're hamstrung from doing significant operations down the line
because you've got your sample rate up too high! Common Sense 101.

Let me tell you why we've got a 96 kHz sample rate system (and - aggh! -
192 kHz too): It makes some people some $$$.

At the outside, these high sample rate systems may have been slightly
beneficial because the anti-aliasing or reconstruction filtering for
some data conversion systems were improved. However, there's no need
to require this through the entire chain! Just do it at the conversion
(e.g., oversample the A/D, then decimate digitally).
--
% Randy Yates % "...the answer lies within your soul
%% Fuquay-Varina, NC % 'cause no one knows which side
%%% 919-577-9882 % the coin will fall."
%%%% % 'Big Wheels', *Out of the Blue*, ELO
http://home.earthlink.net/~yatescr