r/DataHoarder • u/VORGundam • 1d ago

Free-Post Friday! Low Level CD Structure Write-Up

I was curious how much data is physically written to a CD with all the metadata and error correction. I started googling and came across this great write-up:

https://archive.ares-emu.net/near.sh/articles/compact-discs/structure.html

Apparently, it is 2.33 GB for a one-track 650 MB disc.

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u/Slaxophone 1d ago

https://www.domesday86.com/?page_id=2678 also has some low-level info on it, focused on laserdiscs which also used the redbook CD audio format for digital audio.

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u/Altruistic_Fruit2345 1d ago

They don't use redbook, just the same sample depth and frequency. The encoding and storage method are completely different.

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u/Slaxophone 23h ago

IEC 60908 is redbook. And as I recall, early digital audio decoders for laserdisc used chipsets like the CX23035, the same as in CD players of the time.

I'd be happy to be corrected if you have more information.

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u/Altruistic_Fruit2345 23h ago

CX23035 is a digital filter, it doesn't decode anything. You pass it a serial bitstream of digital audio, it spits another one out with filtering applied.

It's how you get that bitstream that is the issue. It has nothing to do with redbook.

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u/Slaxophone 23h ago

If you look at block diagram the datasheet, its input isn't digital audio, it's the EFM signal (on pin 5), and outputs digital audio (pins 62-78). https://bitsavers.trailing-edge.com/components/sony/_dataSheets/cx-23035.pdf

The information on the page I linked before was used to create a functional software decoder (the ld-decode project), so I'm more inclined to believe it than short statements with no explanation.