From Wikipedia (Compact_disc lemma): "[…] The change in height between pits and lands results in a difference in the way the light is reflected. By measuring t

From Wikipedia (Compact_disc lemma): "[…] The change in height between pits and lands results in a difference in the way the light is reflected. By measuring the intensity change with a photodiode […]" I'm no signals expert. Are you saying that there is no quantization in that intensity change measurement? Regardless of quantization, maybe you're right on vibration not being a major source of errors (I know little about electronics and PLLs). But then, what are the error sources that made the engineers put an extra 276 bytes of Reed-Solomon error correction per 2352-byte sector on a mode-1 data CD-ROM (vs none on an audio CD, which has just has the frame ECC and nothing extra). See https://en.wikipedia.org/wiki/CD-ROM#CD-ROM_format https://en.wikipedia.org/wiki/CD-ROM#CD-ROM_format .