[vorbis-dev] Some random thoughts

[Segher Boessenkool]

> Let me first say that efforts such as Ogg shows there is still a lot of
> good in mankind, this is truly a great effort!

Agree eith 2nd, disagree with 1st, I'm afraid. Never has been, either.
 
> While I haven't been lurking, I've been looking through the archives to
> see if this stuff has been discussed before, and I have also tried to read

"delayed lurking"? :-)

> the docs, but a few files aren't there yet. That's OK.
> 
> My primary reason for writing, is a really mindblowing lecture I attended
> a few weeks ago, given by Professor Jaan Pelt of Tartu Observatory in
> Estonia. Professor Pelt argued "don't sample regularily!" If you sample
> regularily, you are limited by the Nyquist theorem, but you're not if
> you don't, so given a finite number of sampling points, you should sample

My ears are limited by hardware, uh, wetware.

> here and there instead of regularily. Research has also been done to
> figure out an optimal sampling strategy. I have very little training in
> signal processing, but it occured to me that this should have applications
> in sound compression. He said that the mathematical basis for this has
> been known for a few decades but that the principles has seen surprisingly
> little use in astronomy, physics, computer science and so on (himself (and
> I) being an astronomer). I thought I'd pass on the idea, just in case...

Taking the same number of samples as in uniform sampling, but instead
uniformly random sampled, will increase the Nyquist freq. to at most double
the normal frequency.

> I guess many Vorbis streams have been sampled long before a Vorbis encoder
> sees them, either being WAV files, or ripping from CDs. In that case, I
> thought that one might compress by actually using an irregular subset of
> the samples, and yet be able restore the sound with good quality. Just a
> thought.

Problem is, only random sampling will help us, and then we will have to include
the sample points in our bitstream.

I will try to find some stuff about this ireegular sampling, 'cause it's a
need idea, anyway. Do you have any pointers to papers etc.?

> Finally, has any thought been given to the possibility of getting the W3C
> to recommend Vorbis like they did with PNG? Well, it doesn't seem to have
> helped the adoption of PNG a lot, but it's a thought.

Not Vorbis, but Ogg.
Sounds great :-) Maybe they even will do it, 'cause ogg is a container format,
i.e. anything can be inside (like in png).

> Keep up the great work!

Ok, ok, I'll send some useful stuff soon. Been a while...

Dag dag,

Segher

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