[alsa-devel] [PATCH] wss-lib: move AD1845 frequency setting into wss-lib

[Takashi Iwai]

At Mon, 12 Jan 2009 17:16:15 +0100,
Krzysztof Helt wrote:
> 
> On Sun, 11 Jan 2009 08:28:13 -0500
> "Theodore J. Allen" <tjallen at hws.edu> wrote:
> 
> > The Soundscape Elite does work, but after a reboot
> > I noticed that there is an oddness in that there's
> > a little "pop" before playing sounds with aplay and
> > a series of short spike pops before the sound plays
> > with xmms, which uses the old oss interface.
> > 
> 
> I traced this and the "pop" sound is caused by two
> things:
> 1. Codec autocalibration every time a new sound is
> started (even when sound is muted it produces
> the "pop" on AD1848).
> 2. Muting sound on and off every autocalibration.
> 
> The OSS code from the 2.4 kernel states that
> autocalibration produced that "pop" so it got
> disabled. This solves two problems at once
> as the muting on and off is not required then
> (and is not done in the code).
> 
> I am not audiofile so I cannot comment how
> audible the lack of autocalibration is. Most
> codecs require it after they are powered up
> (and most of them except the oldest ones
> actually force it after powering up). One can
> autocalibrate the codec only once
> during a card/codec initialization.

Yes, this sounds like a reasonable solution.

> I can prepare a patch which disables the
> autocalibration. This is the only solution
> as I tested others like slow volume muting
> but all others still produce some noise.

In case it really matters, this can be controlled either via a kernel
config or a module option.

But, I have no ISA device (more exactly, a machine with ISA slot) now
for testing, so it's really up to you guys...


Takashi