Relationship between HDCD decoding and jitter / data corruption
May 16, 2002 at 6:12 AM Thread Starter Post #1 of 6

Joe Bloggs

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HDCD is extra information encoded in the last bit of a CD bitstream, right? In order for a HDCD-capable DAC to decode the HDCD information, does it need to read all of these bits correctly? Or is there just a bit of code in the beginning of a track or CD that indicates whether it's HDCD, and then the HDCD decoding is engaged no matter what?

If it is the former, can HDCD decoding be seen as a test for whether a CD transport is reading data off the CD correctly and sending it to the DAC with less jitter than is enough to cause data errors?

OTOH if a HDCD is scratched so that the transport cannot read parts of the track correctly would the DAC indicate that it's doing HDCD decoding even in these parts of the track?
 
May 17, 2002 at 2:57 PM Post #2 of 6

Joe Bloggs

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Well, I haven't got any replies, but I can answer my own question now
rolleyes.gif


Joseph,

Thank you for your interest in HDCD technology. You have many questions
here that are a bit confusing, however I will try to answer them the way
I understand it.

Once HDCD has been detected, you will normally get a light or some other
indication that HDCD is enabled. This indication light will shut off
when HDCD is not detected any longer. This could result if you get
enough transmit errors which timeout the HDCD detection. This timeout
feature is determined by the manufactures and is an unknown length.
Because of this timeout feature you will not be able to tell if the
source bits are in perfect condition or not. If you try to upgrade the
CD or transport device, you may bring in different issues and unknown
sound quality within the unit.

Please feel free to go to our web site and read the FAQ page for
additional Q&A you may have at http://www.hdcd.com

Thanks,
Mike Crystal
HDCD Technical Support
mcrystal@microsoft.com
 
May 18, 2002 at 9:03 AM Post #4 of 6

Joe Bloggs

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Yeah. I suppose it can be used as a preliminary low level test, in that if the HDCD light turns on and off while playing a HDCD, you know that the transport situation is awful as all heck--but just because the light stays on doesn't mean the transport is *good*...
 
May 18, 2002 at 9:26 AM Post #5 of 6

carlo

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bloggs,

i still have to admit i don't understand the point of what you're doing. if by chance there's that many errors off the transfer from the cd to the dac then not only will the hdcd go off, the dac will lose it's "lock" on the frequency. even if that did happen it's not necessarily jitter, but could be a problem in the actual reading of the disc (and several other reasons). if you want to test jitter i suggest looking into the software required, hdcd detection is by no means a measure of it.

best,
carlo.
 
May 18, 2002 at 9:31 AM Post #6 of 6

Joe Bloggs

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Quote:

if you want to test jitter i suggest looking into the software required, hdcd detection is by no means a measure of it.


I can understand that--I suppose I didn't word it correctly...
 

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