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From
SubjectRe: The sound driver
Date
Followup to:  <Pine.LNX.3.95.980213170026.1785A-100000@janus.opensound.com>
By author: Hannu Savolainen <hannu@opensound.com>
In newsgroup: linux.dev.kernel
> >
> > I just noticed that when the sound programs I have request 44,1kHz they
> > only get
> > 42621hz. Is that a bug or what ?
> >
> > I have a DynaQuake 16 , which is 100% pas16 compatible , and i use the
> PAS16 and some other older cards are simply not capable to run exacly at
> 44100 Hz. They produce the actual sampling rate by dividing from a fixed
> crystal oscillator. The nearest possible frequency with PAS16 is 42621 Hz.
>

PAS and PAS16 use a common stock crystal (1.193180 MHz -- I think this
is the same as is used as the clock in a PC; it's an NTSC-derived
frequency, I believe) and divide it; cheap, but poor choice since
common sampling rates are not compatible with the chosen frequencies
-- the proper divisor is approximately 27.056. To make matters worse,
the PAS16 requires stereo sound to use an even divider, which means
the fairly good approximation of 27 (44.192 kHz) is no longer
available, and we're stuck with 28 (42.614 kHz).

When I found this out, I went out and bought a SoundBlaster 16.

Incidentally, the lowest frequency I have found that is an even
multiple of all commonly used sampling frequencies is 7.056 MHz. It
uses a divider of 160 for 44.100 kHz and a divider of 147 for 48 kHz.

-hpa
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