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In Reply to: RE: Digital recorder question posted by Goober58 on May 17, 2025 at 16:57:15
Isn't a small part of the "problem" that, in order to bolster the robustness of the data, one bit of the 16-bit word is not a datum that represents digitized music, it is a "Checksum" bit. So, there are only 15 bits available for recording, at best.
The purpose of the "Checksum" bit is to indicate whether summing the other 15 bits results in an Odd or an Even sum (or total). If there is a conflict between the sum and the Checksum, Error Correction kicks in.
Pretty darn clever, I thought back in 1983, or whenever it was I was recruited to write for Digital Audio magazine. I was also impressed by the Reed-Solomon Interleave Code.
Like Roseval says it's a sign bit. If it were a checksum a 16 bit recorder would be completely useless as a lossless recorder instead of very difficult to use as one.
Edits: 05/19/25 05/19/25
I don't blame you to think so in 1983. Almost none of us did understand digital at that time.
Today we know the MSB is not a checksum (parity) but a sign bit. It simply tells you if the values are negative (-32768) or positive (+32767).
https://en.wikipedia.org/wiki/Compact_Disc_Digital_Audio
Edits: 05/19/25 05/19/25
Someone in different circumstances (and with a different personality) might have saved every scrap of "official" communication from the Compact Disc Group, or whatever was the name of the public-relations collaborative in NYC that was funded by the various industry participants.
I definitely remember setting aside time to read all the stuff about how wonderfully robust S/PDIF-System CDs were.
I vividly recall that the staff at DIGITAL AUDIO review decided that the WORST EVER CD TO DATE was by Zubin Mehta's son Bejun, who was a Boy Soprano.
So, they decided to sacrifice that CD to a Torture Test. Does anyone else remember that?
I thought it was gratuitously cruel.
They smeared Peanut Butter on it, etc.
About Checksum vs. +/- Sign--that bit is still not available for music data, right?
ciao,
saintjean
CD is 16 bit PCM audio.
Might it be you are mixing up CD and S/PDIF?
S/PDIF is a 32 bit word with 24 bits reserved for audio and a 8 bit preamble. One of this 8 bits is a parity bit so the receiver can check the integrity of the data.
The Well Tempered Computer
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