Device app - VideoDeviceController matched to IDeviceIoControl object

Question

I have a webcam related DeviceApp which accesses standard properties via the VideoDeviceController and custom properties through IDeviceIoControl without problem.  (To access custom properties, I use Windows::Devices::Enumeration to get a list of device paths.)

This all works fine if there is only one camera.  Only one enumerated path will successfully result in a IDeviceIoControl object and I can assume it's the same device represented in VideoDeviceController.  But if there are multiple cameras attached, then I don't know which enumerated path matches the device represented in the VideoDeviceController.

Is there any way to get more device information from the VideoDeviceController?  If I could get vid/pid info, I might be able to match that with the enumerated data.

Is there a solution to this or do need to resort to MFT?

Thanks.

Answer 1

Gary,

I am looking into this for you.

Best Wishes - Eric

Answer 2

Gary,

The following should work great for you:

http://msdn.microsoft.com/en-us/library/windows/apps/windows.devices.enumeration.deviceinformation.properties.aspx

http://msdn.microsoft.com/en-us/library/windows/apps/hh464997.aspx#ListOfCanonicalProperties

You might be able to us these slightly simpler calls (I am not sure they will return enough information however):

http://msdn.microsoft.com/en-us/library/windows/apps/br225393.aspx

http://msdn.microsoft.com/en-us/library/windows/apps/windows.devices.enumeration.deviceinformation.id.aspx

http://msdn.microsoft.com/en-us/library/windows/apps/windows.devices.enumeration.deviceinformation.name.aspx

Best Wishes - Eric

Answer 3

Hi Eric,

Thanks for the response.  These links will be very helpful.  However, it still does not connect the enumerated device and the device represented by the VideoDeviceController.

I think the answer is to use the MFT, which, according to various sources, can be used to control custom properties as well as modifying the image.  But I haven't found a sample doing this. 

I have successfully built the sample MFT and got it working with my own app.  I can apply an algorithm to alter the frames for effect such as grayscale.  That's fine, but what I want to do is access custom properties in my driver.  In the MFT code there is a lot of information but I'm not sure what to use to connect with the driver for the device instance at hand.

For example, in the MFT, I can use IMFTransform to get the following string (via IMFAttributes/MFT_ENUM_HARDWARE_URL_Attribute):

\\\\?\\USB#VID_046D&PID_082D&MI_00#6&25f03fb2&0&0000#{e5323777-f976-4f5b-9b55-b94699c46e44}\\{bbefb6c7-2fc4-4139-bb8b-a58bba724083}

I could parse this and replace the generic webcam guid with my own guid so I can open a IDeviceIOControl object.  But this would be a risky hack since the device path structure appears not to be documented.

What would be ideal would be something like this:

    devpath = GetDevicePath ( inputStreamId, <my guid> )

I'll keep looking around the various interfaces exposed in the MFT.

BTW, I have been going over the following:

Metro style Device Apps for Cameras (dated May 31, 2012)
http://msdn.microsoft.com/en-us/library/windows/hardware/hh454870.aspx

Similar post
http://social.msdn.microsoft.com/Forums/nl/tailoringappsfordevices/thread/da145ce6-3e66-4562-8631-f93a5709a500

Answer 4

Gary,

I am looking into this for you.

Best Wishes - Eric

Answer 5

Gary,

Still working on this.

Best Wishes - Eric 

Answer 6

Gary,

I did post an update to the on thread you mention (Does it clarify things at all?):

http://social.msdn.microsoft.com/Forums/nl/tailoringappsfordevices/thread/da145ce6-3e66-4562-8631-f93a5709a500

Best Wishes - Eric

Answer 7

Actually I responded to this on also with the same answer:

http://social.msdn.microsoft.com/Forums/nl/tailoringappsfordevices/thread/da145ce6-3e66-4562-8631-f93a5709a500

Best Wishes - Eric

Answer 8

Gary,

We did just post a sample of a Metro style app accessing MFT0 (Look at the JavaScript version):

http://code.msdn.microsoft.com/windowsapps/Metro-style-device-app-for-4f39b7bf

The JavaScript version of the app access the MFT0.

Best Wishes - Eric

Answer 9

Hi Eric,

Sorry for the late reply.
I downloaded the latest Metro-style-device-app example (I had already downloaded this on 6/6) and I see that a line has been added to the wrapper

    Microsoft::WRL::ComPtr<IMFTransform> m_spMft;

My problem is not how can we get this interface to the DeviceApp (as shown here).  I can always add methods to the MFT0 interface for access from the device app and work with the MFTransform in the MFT code directly.

The problem is that I don't know how wo use IMFTransform to access custom driver properties.  IMFTransform has access to a lot of information and I've tried working with some of it, but with no luck.

Thanks,

Answer 10

Gary,

Are you referring to the JavaScript C++ version of the sample?

Best Wishes - Eric

Answer 11

Yes.

Answer 12

Gary,

Could you list a couple of properties you would like set?  Are you trying to do this with the MFT0? 

Best Wishes - Eric

Answer 13

Hi Eric,

After learning more about the driver MFT (and MFTs in general), I see that IDeviceIoControl should be used to access custom driver settings not MFT.