Re: [alsa-devel] [PATCH] wss-lib: move AD1845 frequency setting into wss-lib
On Sun, 11 Jan 2009 08:28:13 -0500 "Theodore J. Allen" tjallen@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.
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.
Regards, Krzysztof
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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@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:
- 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
participants (2)
-
Krzysztof Helt -
Takashi Iwai