cliveb;194831 Wrote: > With suitable dither, it's also possible to hear signal below the noise > floor of a digital signal, of course. >
But the theorem doesn't say you can't recover some signal below the noise - in fact it tells you exactly how much of it you can! Even if S/N < 1 the capacity can still be arbitrarily large; in the limit S/N<<1 the theorem says C = B*(S/N), where B is the bandwidth. So there can be plenty of recoverable information in signal below the noise floor, and the fact that we hear it on vinyl is a statement about that specific form of data storage, but doesn't say much about the maximum attainable capacity. Patrick Dixon Wrote: > > Shannon Hartley deals with digital information on an analogue medium, > which analogue audio on a vinyl LP isn't. I have no idea what you mean by "digital information". There's no such thing - you can store information in digital or analogue form, but it's the same information. An LP is a perfectly good example. > It may be, that if you really wanted to store digital information on > vinyl, there is a more optimum choice of bandwidth vs SNR that could be > used - rather than that used for analogue audio, which is naturally > tailored to what we require to reproduce music. Again, you seem to be rather confused. We aren't interested in storing digital data on vinyl, whatever that means. S-H tells us the maximum possible information capacity of a noisy analogue channel with bandwidth B, signal S, and Gaussian noise N. It doesn't tell us what that best compression scheme is for a given piece of information - it just tells us how well we could ever do. So when we compute these numbers, we are comparing the best possible case for CDs versus the best possible case for vinyl. Depending on exactly what is your goal, generally neither one of those media comes close to that, since in neither case is there any compression. For example if your goal was to record only the components of music we can hear, a recording made at a higher than CD sampling rate and bit depth, run through a psychoacoustic filter and compressed down to CD rate would be closer to the Shannon limit than a standard CD recording. That's why there are some differing estimates above - if we assume we can't hear above 20 kHz, vinyl "wastes" its (putative) bandwidth above that. CDs on the other hand reproduce only up to 22 kHz, and so make a more efficient use of the possible capacity. -- opaqueice ------------------------------------------------------------------------ opaqueice's Profile: http://forums.slimdevices.com/member.php?userid=4234 View this thread: http://forums.slimdevices.com/showthread.php?t=34379 _______________________________________________ audiophiles mailing list [EMAIL PROTECTED] http://lists.slimdevices.com/lists/listinfo/audiophiles
