Re: Maintaining sound card at a specific frequency

[Takashi Iwai <tiwai@suse.de>]

At Tue, 18 Jan 2005 09:45:41 -0800,
Mark Knecht wrote:
> 
> On Tue, 18 Jan 2005 18:31:28 +0100 (CET), Giuliano Pochini
> <pochini@denise.shiny.it> wrote:
> > 
> > 
> > On Tue, 18 Jan 2005, Takashi Iwai wrote:
> > 
> > > > IMHO we should think on a good solution for this problem. Some
> > > > cards have many channels/voices but the sample rate is common
> > > > for all of them. Currently the only clean way to manage it is
> > > > a control that locks the sample rate at a given frequency, but
> > > > it isn't a nice solution because it requires explicit user
> > > > intervention. In the echoaudio driver I implemented a kludge
> > > > that automatically locks the sample frequency in order to avoid
> > > > unwanted rate changes.
> > >
> > > You can add a control to lock the sample rate (e.g. ICE1712).
> > 
> > Yep, I know, but it's not part of the pcm API: applications do not
> > lock the sample rate themselves. The user has to do it manually. This is
> > why I choosed an alternate solution. If apps were able to lock the rate it
> > would be very useful. It may need some help from the driver, though.
> > 
> But that sort of application level control is actually what's causing
> me problems. Mozilla browses around and changes the frequency of the
> card, independent of what the overall system architecture requires.
> 
> Again, I think you're probably right about this issue for a completely
> stand-alone system, but for a multi-PC system I think some sort of
> plughw solution that resamples in software when necessary would work
> better for me and Mozilla.

When the rate is locked in the system (as in my patch), plughw should
work as you expected.


Takashi


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