Posted by Matthew L. Martin on 11/10/06 00:14

Randy Yates wrote:
> Tom Stiller <tomstiller@comcast.net> writes:
>
>> In article <11s4h.1084$GS2.1008@newssvr14.news.prodigy.com>,
>> "Guest" <llcoolj@comcast.com> wrote:
>>
>>> If you are not used to dealing with high resolution video in it's purist
>>> form and only came aboard recently, then your eye for spotting resolutions
>>> and details may not be as sharp as others. I have been dealing with
>>> high-res video since 1990. I had the Laserdisc, S-VHS VCR, various DVD
>>> players and HD. I know what the deal is.
>> The issue raised has nothing to do with the quality of high resolution
>> video or the sound quality of audio, but rather can a wire, or fiber,
>> transmitting a bit serial stream compromise the quality of the
>> reconstructed analog signal.
>
> Actually, it can. I'll have to back-peddle a little here.
>
> S/PDIF is a single-wire interface that embeds the clock with the data.
> Because of this, problems with the interface that aren't serious
> enough to cause bit errors can still affect the sound by affecting the
> quality of the recovered clock. A PLL is used to recover the clock,
> and depending on the type of loop filter used in the PLL, input noise
> from cable degradations could introduce jitter into the digital clock
> and thus the reconstructed analog signal.
>
> How audible is it? That is a whole dissertation unto its own.

According to test I did years ago when I had access to the proper
equipment the jitter induced sidebands on an impaired cable were 85dB
below the program material (CD test tones). One golden eared guy
duplicated my results with similar equipment, but he claimed he could
hear 85dB below the program material, so the jitter was audible to him.

Matthew

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You can't win
You can't break even
You can't get out of the game

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