[oclug] Scratchy sounds from XMMS

[Mike Warnecke]

I've never used that card, so I can't give you any advice on it, except xmms
does the decompression from MP3 into a more natural sound format your card can
understand, the card only cares about that information.  Other comments are
in-line.

Jon Earle wrote:

> I worked around it by tuning the settings for XMMS's mpg123 plugin to use
> 8bit resolution vs 16bit (can someone explain what that means please).  It

This is called quantization.  Sound looks like a wave(like a sine wave), which
is analogue and has an infinite number of values between its top(crest) and
bottom (trough).  A computer can only store finite numbers, so it divides the
wave into segments.  8 bits means you get 256 different segments which is a fair
approximation of the real sound.  16 bits means there are 65536 segments which
is a much better approximation of the real sound.  When turning this data back
into sound, the sound wave is similar to the original because it passes through
those points again.  Naturally the reproduced sound is analogue too.

>
> doesn't really sound any different, but the scratchiness seems gone.

16 Bit should sound better, depending upon the fidelity of your sound
equipment.  Unless you're an audiophile, you might not care.

>
> What is this "realtime" priority - is it an XMMS option?

I don't think ordinary Linux does real-time scheduling yet.  Solaris, Lynx,
RTLinux and a few other Unices do.  I wouldn't worry about this unless someone
will die if XMMS runs out of CPU cycles.  I don't think a little skip is that
bad.  Real-time ensures that a process is guaranteed timely CPU access when it
needs it.

--
Mike Warnecke           | Wow, do you really need 500 million
IT Manager              | instructions per second to balance
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Century Sound & Music   | GNU/Linux,Open Source. What really compute.