Re: CD's, C64's and error-correction

From: Martijn van Buul (
Date: 1999-10-08 09:37:58

John West McKenna wrote:
> That's not correct - Audio CDs have extremely good error correction.  You

If you use them for the goal they have been invented for, yes.

> can completely remove all data in a slice a couple of mm wide with no
> effect on the output at all.

Correction - no -audible- effect on the output. CD-players are fairly
good in interpolating a signal (which isn't that difficult, as long
as it's music). CD-ROMs are stuffed with CRC-checks, and have a 
considerably lower capacity than a bare CD-audio.

The maximum capacity of a cd-Audio is 441000 (samples/s) * 4 (
bytes/sample) * 74 * 60 = 746.9 MB, while the maximum capacity of a 
normal CD-ROM is only 650 MB.

The differences are purely CRC-codes and similiar anomalies :)

> Part of the design spec for CDs was that they had to be very cheap to make.
> That means the information on them has to be very tolerant of manufacturing
> faults.  That means very good error correction.

Let me put it this way. Suppose there's an error somewhere on a CD, say
for 100 samples. The CD just can't read it, and has to interpolate, and 
inserts data that won't sound too awful. A human mind won't notice
the difference, since its a) a very short error (2 ms) and b) masked.

However, in our case, 100 bits would have been lost.

    Martijn van Buul - -
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