[MPlayer-users] A question...

[D Richard Felker III]

On Sun, Feb 09, 2003 at 10:19:19PM +0000, Jon Larabee wrote:
> Which is a little endian and is defaulted to 16 bit samples. I have been
> using a signed short to pull them out of a file after recording for
> analyzation. This has worked quite well indeed. I have svga graphing
> software I have written to handle and scale the values, it makes a pretty
> picture, but unfortunatly... I am having trouble conceptionalizing what it
> is supposed to mean. From the OSS site, the proposed meaning of a sample
> is the volume of the signal when it is measured. The thing is... How does
> one have negative volume? The threshold I imagine is zero, or is it that I

Well volume is a bad word for it; the best word is probably amplitude.
It can be positive or negative because voltage can be positive or
negative (i.e. higher or lower potential in the signal line than in
the ground) and because pressure on your eardrum can be inward (above
the pressure inside your ear) or outward (below internal pressure) as
the vibration of the sound goes back and forth. Which direction is
which isn't terribly important.

> am simply looking at it wrong and that some other value is the threshold
> that I should be concerned with? Is there a way I can relate this value to
> frequancy? Any help anyone could offer in this direction would be most

This is a very good question. There is no direct way to get the
frequency since the concept isn't even really well defined. Chopping
up the sound into blocks and applying a fourier transform of some sort
is the most common way I know of extracting frequency information.
There are also various filters and wavelet type techniques I don't
really know much about.

Anyway, if you're seriously planning on analyzing sound like you say,
you really need to get yourself a good text on the subject and read
up...

Good luck!

Rich