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Re: information theory?
Posted:
Nov 4, 2011 6:31 AM
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On 04/11/2011 09:33, Peter Webb wrote:
>
>
>
> He estimated music contains 40 bits/second entropy.
> How close is MP3 to that?
>
> ___________________________________
> I doubt surprised Shannon said that, and if he did its somewhere between
> meaningless and wrong.
>
If Shannon did make the statement attributed to him above (and I
seriously doubt it) - I would like to see references.
> CD quality mp3s are roughly equivalent to 178 kbps, over 4,000 times his
> estimate. But then you can encode a lot of sounds that most people would
> not consider music. And it stereo, so you can halve it if Shannon was
> talking about mono.
>
> And how do you define music, except as sound? And random sound waveforms
Have you never seen sheet music? That is what Shannon was estimating -
the bitrate for describing music in the abstract. There are a finite
number of notes, durations and amplitudes in a classical composition.
I suspect 40 bits/sec is still far too tight, but a midi stream using a
high end reconstruction codec represents a pretty good example of what
is possible by way of compression for *music* as opposed to voice or a
random noise stream.
> cannot be compressed on average at all. To get a smaller figure for
> music, you have to define what subsets of sounds are music. Lots of luck.
I think that may have been his intention although I don't actually
recall seeing the 40 bit/s number originally attributed to him above.
As I said if he did anything I think he was estimating the information
content of music in the already concise form of an orchestral score.
>
> The real number probably lies somewhere between 178 kbps and 40 bps. The
> actual number is the base 2 logarithm of the number of different 1
> second sound bites that the ear can distuingish and would consider as
> music. I doubt even Shannon would have known the answer to that equation.
Maybe he didn't consider all the alternative atonal and continuous
frequency synthesisers of arbitrary waveforms that are possible now - or
perhaps it was a subtle dig at Stockhausen and Schoenberg as not music.
Be interesting if the reference to this paper can be found to see how he
allocated those 40 bits/s....
I reckon at a bare minimum about 7 to the note, 8 to amplitude, 6
duration, 5 to the instrument - and it is already obvious that you
cannot encode more than a single note per second at this bitrate.
Can anyone provide a citation to this alleged paper on music bitrate?
--
Regards,
Martin Brown
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