Windows is not giving you a buffer because it doesn’t know how big of a buffer
to give you.
For documentation on writing kernel streaming property handlers directly, see
https://docs.microsoft.com/en-us/windows-hardware/drivers/audio/audio-property-handlers
- in particular
Before submitting a get-property request to retrieve a property value, the
client should allocate an output buffer into which the miniport driver's
property handler can write the property value. For some properties, the size of
the output buffer is device-dependent and the client must query the property
handler for the required buffer size. In these cases, the client submits an
initial property request with a zero-length output buffer. The handler responds
by returning the required buffer size along with the status code
STATUS_BUFFER_OVERFLOW. (The handler writes the required size into the
ValueSize member of the PCPROPERTY_REQUEST structure.) The client then
retrieves the property value by allocating an output buffer of the specified
size and sending this buffer in a second get-property request.
From: Yudi Cao<mailto:yudi.cao@xxxxxxxxx>
Sent: Monday, May 8, 2017 1:40 AM
To: wdmaudiodev@xxxxxxxxxxxxx<mailto:wdmaudiodev@xxxxxxxxxxxxx>
Subject: [wdmaudiodev] How to implement KSPROPSETID_AudioSignalProcessing
Property Set in AVstream mini-driver
Hello,
I'm working on an AVstream audio driver for USB Headset (add some extra formats
comparing to inbox usbaudio.sys).
To integrate APO DLL to my driver package, I need implement the
KSPROPSETID_AudioSignalProcessing property set.
The property set AutomationTable definitions are below:
DEFINE_KSPROPERTY_TABLE(AudioFilterPropertySetTable)
{
DEFINE_KSPROPERTY_ITEM
(
KSPROPERTY_AUDIOSIGNALPROCESSING_MODES, // property item
defined in ksmedia.h
CCaptureRenderFilter::FILTERPROP_PropertyAudioSignalProcessing,
sizeof(KSP_PIN), // minimum buffer length for
property
0, // minimum buffer length for returned data
NULL,
NULL, // default values
0, // related properties
NULL,
CCaptureRenderFilter::FILTERPROP_PropertyAudioSignalProcessingBasicSupport,
0 // don't serialize
)
};
DEFINE_KSPROPERTY_SET_TABLE(AudioFilterProperties)
{
DEFINE_KSPROPERTY_SET
(
&KSPROPSETID_AudioSignalProcessing, //
property set defined in ksmedia.h
SIZEOF_ARRAY(AudioFilterPropertySetTable), // the properties
supported
AudioFilterPropertySetTable,
0, // reserved
NULL // reserved
)
};
DEFINE_KSAUTOMATION_TABLE(AudioFilterAutomationTable) {
DEFINE_KSAUTOMATION_PROPERTIES(AudioFilterProperties),
DEFINE_KSAUTOMATION_METHODS_NULL,
DEFINE_KSAUTOMATION_EVENTS_NULL
};
m_KSFilterDesc.AutomationTable = &AudioFilterAutomationTable;
The function declared as below:
NTSTATUS CCaptureRenderFilter::FILTERPROP_PropertyAudioSignalProcessing(IN PIRP
pIrp, IN PKSP_PIN pKSP_Pin, IN OUT PKSMULTIPLE_ITEM pData)
NTSTATUS
CCaptureRenderFilter::FILTERPROP_PropertyAudioSignalProcessingBasicSupport(IN
PIRP pIrp, IN PKSP_PIN Request, IN OUT PVOID Data)
The problem is:
The system will call FILTERPROP_PropertyAudioSignalProcessing() for several
times with the pData==NULL. Why the pData is always null?
What's wrong with my code? Is there anywhere to get some sample code for
AVStream mini-driver to support KSPROPSETID_AudioSignalProcessing?
Thank you for your help,
Hunter
