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Slink-e / CDJ Discussion Archive #10

Calculating the CRCC for the Q-Subcode on SPDIF

Posted By: Colby Boles <cboles@n...>
Date: 11/4/00 11:20am

My turn to ask a question :)

I'm writing a program to record digital audio to disk using a RME Digi96 sound card. I'm using the Q-Subcode information on the SPDIF signal to divide the tracks as exactly as I can. I've noticed that the Q-Subcode has errors in it occasionally and I would like to be able to identify and ignore these Q-Subcode frames by checking them against their included CRCC, but I'm running into a couple of problems:

1) I don't know what method is being used to calculate the CRCC. I've tried all 16-bit polynomials, but haven't found a consistent match. Maybe I'm running the block through the shift registers in the wrong byte/bit order?

2) The Q-Subcode frame is 98 bits long on the CD, but only 96 bits in size on the SPDIF signal (missing the S0 and S1 bits), so hopefully the CRCC doesn't use S0 and S1 right? I guess I could do a CRCC against all 4 possible S bit combinations...



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