> Vibration is one of the factors that would make the same audio CD, read with the same CD player, produce different digital signals some of the time or even every time.
Err, no.
That makes sense when you have an analog version of the audio picked up by an analog transducer (i.e. a vinyl record) but makes no sense with an isochronous stream of quantized samples.
I suppose a vibration could cause a small phase shift in when the sample physically appears under the LED, but but since the D->A conversion is clocked by a PLL it is irrelevant.
If you have extreme warping or shaking (e.g fling your discman onto the floor or stick your finger on the disk while it's spinning) then a sample might not appear at all, but that's something different than you are talking about.
I suppose it's theoretically possible that some extreme warping or vibration could cause a bit flip, but that's what the ECC is for.
"[…] 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 .
There was a day when the clock going in to the D/A converter could be affected by the bitstream coming off the CD. Those days are long gone I'm sure. Everything is buffered in RAM, overclocked, and digitally processed before it hits the D/A.
Err, no.
That makes sense when you have an analog version of the audio picked up by an analog transducer (i.e. a vinyl record) but makes no sense with an isochronous stream of quantized samples.
I suppose a vibration could cause a small phase shift in when the sample physically appears under the LED, but but since the D->A conversion is clocked by a PLL it is irrelevant.
If you have extreme warping or shaking (e.g fling your discman onto the floor or stick your finger on the disk while it's spinning) then a sample might not appear at all, but that's something different than you are talking about.
I suppose it's theoretically possible that some extreme warping or vibration could cause a bit flip, but that's what the ECC is for.