[wdmaudiodev] Re: External clock synchronization and sample rate issue

  • From: "Jeff Pages" <jeff@xxxxxxxxxxxxxxxx>
  • To: <wdmaudiodev@xxxxxxxxxxxxx>
  • Date: Thu, 11 Jan 2007 13:33:58 +1100

I've found under Vista stopping and starting drivers is quite fast - we have a FM radio capture card that creates 24 capture devices, and I can stop and start that in just a second or two on Vista whereas on XP you just about die of old age waiting for it!


----- Original Message ----- From: "Matt Gonzalez" <matt@xxxxxxxxxxxxx>
To: <wdmaudiodev@xxxxxxxxxxxxx>
Sent: Thursday, January 11, 2007 1:29 PM
Subject: [wdmaudiodev] Re: External clock synchronization and sample rate issue


OK, so you don't allow the sample rate to be set by Windows. That would certainly work.

My descriptors are all built dynamically, so I wouldn't need different subdevices for the different rates.

I don't like stopping and restarting the driver 'cos it takes so long to restart when you have a lot of audio devices. I guess if that's what you have to do, then that's what you have to do.

Matt

Jeff Pages wrote:
Matt,

My card sounds very similar with multiple inputs and outputs driven by a common clock. I use a property page accessible from Device Manager to set the card clock, storing the clock value under the device's hardware registry key and setting the DI_FLAGSEX_PROPCHANGE_PENDING flag on exit which forces the driver to be stopped and restarted.

The driver, on starting, reads the clock setting from the registry and activates the appropriate set of wave subdevices for that sampling rate.

Jeff

----- Original Message ----- From: "Matt Gonzalez" <matt@xxxxxxxxxxxxx>
To: <wdmaudiodev@xxxxxxxxxxxxx>
Sent: Thursday, January 11, 2007 12:00 PM
Subject: [wdmaudiodev] Re: External clock synchronization and sample rate issue


OK, that makes sense. So you know when you create the subdevice that you are only supporting one sample rate.

The problem I have is somewhat different - my driver creates multiple subdevices for each pair of inputs and outputs on the card. All the subdevices share a common , internally generated hardware clock, so you would want to specify the same preferred format for all the inputs and outputs. Obviously, having to go through the control panel and setting the preferred format for each audio device is not desirable. It seems like in that case, you'd want to allow the full range of sample rates to be available. But then - if you change one device, is there some way to propagate the change to all the others? The discussion so far suggests that there is no way to do this automatically.

I'm thinking here of something along the lines of the IPortEvents interface, but I'm just spitballing.

Matt


Jeff Pages wrote:
No, I don't call IoSetDeviceInterfaceState anywhere - presumably the port class takes care of enabling device interfaces when the subdevice is registered. Only one wave subdevice is ever created at a time, it's just that it might have different parameters (specifically supported sampling rate) depending on what the hardware clock is when the subdevice is created. I think a different subdevice name is needed for each option because Vista stores the audio engine rate in the registry for each one.

Jeff

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