Hi,
I develop and maintain an ASIO/AVS WDM driver for Windows. The driver is
used for multi-channel devices.
Per design and customer requirement the sample rate of the device is set
with the ASIO control panel or the ASIO interface, or is given by
digital audio input (S/PDIF). When the sample rate is changed by the
user the AVS driver is disabled and re-started using PDO states of my
bus driver.
The AVS driver offers exactly the sample rate to Windows that is
selected by the user on ASIO interface.
Starting with Windows Vista the sound dialog offers the advanced tab to
select the sample rate and format. Unfortunately this value is cached by
the system during first enumeration after installation in registry:
\\Registry\\Machine\\Software\\Microsoft\\Windows\\CurrentVersion\\MMDevices\\Audio\\<Capture|Render>
The multi-channel device is exposed as up to 8 render and up to 8
capture device device, each with two channels. It is no practical option
for the user to open all dialog boxes and switch the sample rate to the
new one after changing it in ASIO. Without doing this the devices cannot
be used.
I have seen several discussions like:
//www.freelists.org/post/wdmaudiodev/setting-sample-rate-in-the-control-panel-in-Vista,4
but I did not see a solution for this problem.
My current workaround is the following:
I enumerate the following keys from kernel driver
L"{f19f064d-082c-4e27-bc73-6882a1bb8e4c},0"; // PKEY_AudioEngine_DeviceFormat
L"{e4870e26-3cc5-4cd2-ba46-ca0a9a70ed04},0"; // PKEY_AudioEngine_OEMFormat
L"{3d6e1656-2e50-4c4c-8d85-d0acae3c6c68},2"; // unknown
L"{a2a3fff4-353f-407c-9d86-1f9dc7d5a606},2"; // unknown
The keys contain one or more serialized PROPVARIANT structures, with a
blob type and the data structure WAVEFORMATEX. I fix the data structure
with the current sample rate before creating the filters. This seems to
work but is not stable related to operating system changes. E.g. Windows
10 anniversary update has modified the data structures.
I have also considered the option to use KsPinGenerateEvents(KSPIN,
KSEVENTSETID_PinCapsChange, KSEVENT_PINCAPS_FORMATCHANGE, ...), but my
problem is: in error case no KsPin is created and for that reason I
cannot call it.
The access from user mode seems to be possible with
IPropertyStore::SetValue(), but it requires administrator privileges and
the data format for the unknown GUIDs is not documented. I do not see an
advantage in comparison to my existing workaround when using this interface.
Is there in the meantime an API for Windows 10 or a workaround to set
the sample rate for an audio device by program?
Thank you.
Regards,
Guenter Hildebrandt
--
Dr. Günter Hildebrandt
Senior Software Developer
