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Posted by Randy Yates on 11/08/06 22:46
Jim Gilliland <usemylastname@cheerful.com> writes:
> Guest wrote:
>> Jim Gilliland wrote:
>>> Guest wrote:
>>>
>>>> I have read over the last few years about HDMI/DVI cables being all
>>>> the same regardless of build quality because "ones and zeros are
>>>> ones and zeros. It either works or it does not." This type of
>>>> reasoning makes sense on it's face, but then I recalled having a
>>>> Monster Cable optical cable and then an Acoustic Research optical
>>>> cable and I noticed a very big difference in sound quality. The AR
>>>> outperformed the Monster to a very larger degree.
>
>>> Really? Can you describe the difference between the sound of the two
>>> cables?
>> Yes. The Monster sounded flat (some people may love that) and lower
>> in volume. It lacked detail, kick and bass. The AR had kick,
>> clarity, bass and it was louder. It gave the music and surround
>> sound true impact.
>
> And to what do you attribute this difference in sound? How do you
> suppose the cable altered the bit stream to cause the audible
> difference that you believe you heard?
>
> I'm not sure how to interpret words like "kick" and "impact", but
> words like "louder" and "bass" have a fairly specific meaning. In
> order to impact the volume of a digital signal, some fairly simple
> arithmetic needs to take place. In order to impact just the low
> frequency portion of the signal, some rather more sophisticated
> arithmetic must take place.
>
> Apparently, one (or perhaps both!) of your cables is able to do some
> fairly sophisticated digital processing - changing the bitstream in
> such a way that the values carried by each 16-bit word were modified
> to create more or less bass.
>
> Changing the bass characteristics of the music would require that your
> cable change each successive 16-bit word in exactly the right
> direction (some values increased, some decreased, some left unchanged)
> in exactly the right sequence over an extended period of time. And it
> would have to do all that without losing any of the signal bits
> (pre-emphasis and so on), nor mixing up any of the interleaved samples
> for the right and left channels.
Jim,
You forgot to mention that this feat would also require scaling the
convolution sum (from the bass FIR filter) appropriately with the
right number of guard bits and the right requantization back to the
native data path width, possibly utilizing psychoacoustic noise-shaping.
> I think this is an amazing discovery! You shouldn't be telling us
> about it here - you should be documenting your discovery and sending
> it to the Patent Office! Imagine that a simple piece of fiber can do
> processing that we thought required a sophisticated DSP integrated
> circuit. What a wonderful world we live in!
Indeed.
--
% Randy Yates % "My Shangri-la has gone away, fading like
%% Fuquay-Varina, NC % the Beatles on 'Hey Jude'"
%%% 919-577-9882 %
%%%% <yates@ieee.org> % 'Shangri-La', *A New World Record*, ELO
http://home.earthlink.net/~yatescr
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