selecting a device without UI

V_shr

the webcams connect with USB port , and their drivers are installed , I looked msdn an I found this :

Call "CoCreateInstance" to retrieve a pointer to the "IWiaDevMgr" interface.
Use the "IWiaDevMgr::EnumDeviceInfo" method of the "IWiaDevMgr" interface to obtain a pointer to the "IEnumWIA_DEV_INFO" interface.
Use "IEnumWIA_DEV_INFO" interface to obtain "IWiaPropertyStorage" interface pointers for each WIA device enumerated.
Use "IWiaPropertyStorage" interface to inspect the device information properties of each device and save the "WIA_DIP_DEV_ID" property from the desired device.
Use the "DeviceID" property with the "IWiaDevMgr::CreateDevice" method in the "IWiaDevMgr" interface to create a WIA device object. The "IWiaDevMgr::CreateDevice method" provides the application with the pointer to the IWiaItem interface of the root item of the specified device.

example for create a device :

HRESULT CreateWiaDevice( IWiaDevMgr *pWiaDevMgr, BSTR bstrDeviceID, IWiaItem **ppWiaDevice )
{
//
// Validate arguments
//
if (NULL == pWiaDevMgr || NULL == bstrDeviceID || NULL == ppWiaDevice)
{
return E_INVALIDARG;
}

    //
    // Initialize out variables
    //
    \*ppWiaDevice = NULL;

    //
    // Create the WIA Device
    //
    HRESULT hr = pWiaDevMgr->CreateDevice( bstrDeviceID, ppWiaDevice );

    //
    // Return the result of creating the device
    //
    return hr;
}

I know that this is what I need , but I cant understand it . plz help me

Justin Tay

What are you doing exactly? Choose it to do what? Are you using DirectShow? If so just get the System Device Enumerator and use the ICreateDevEnum interface to enumerate the CLSID_VideoInputDeviceCategory. http://msdn.microsoft.com/library/default.asp?url=/library/en-us/directshow/htm/usingthesystemdeviceenumerator.asp[^]

V_shr

// Activate (with the Default/first device) SelCapDrvProc(hwndMain,WM_COMMAND,SELCAPDRVDLG_BUTTON,0); and this actives the default (first) camera and I want to change the default .

Justin Tay

From google it looks like you are making reference to some code in some project available on Planet Source Code? Edit: I've found the source from Planet Source Code. It uses Video For Windows, so I'm not sure what your previous post was about. For reference the source is located at http://www.planet-source-code.com/vb/scripts/ShowCode.asp?txtCodeId=2679&lngWId=3[^] You would like to use this and just change it to use a particular webcam? You could just modify EnumCapDrv and only add that particular webcam to the listbox. The code for the project in general looks like it could be a little buggy, but I think it already demonstrates everything you want to know? Like getting devices using capGetDriverDescription()? -- modified at 5:34 Thursday 4th May, 2006

V_shr

this is the link to download code: http://www.planet-source-code.com/upload_PSC/ftp/My_Webcam853695202002.zip[^] note : if you haven't CBuilder you can open main.cpp and main.h with notepad .

Justin Tay

Looks like it's based on the project that I found. Look at the edited post above this one for comments. As I mentioned earlier look at EnumCapDrv, it calls capGetDriverDescription() to get devices. From looking at the API again though, my initial idea is wrong. Looks like you specify the device from the index.

for (i=0; i<10; i++)
{
if(capGetDriverDescription(i, szDeviceName, sizeof(szDeviceName),
szDeviceVersion, sizeof(szDeviceVersion)) )
{
if(strcmp(szDeviceName, "MyDeviceName") == 0)
{
SendMessage( hwndVideo, WM_CAP_DRIVER_CONNECT, i, 0L);
}
}
}

Anyway i think the code is a bit buggy.

// get the selected driver
SendMessage( hwndSelCapDrvDlg_LBox, LB_GETSELITEMS, 1, sel);

Shouldn't it be

// get the selected driver
SendMessage( hwndSelCapDrvDlg_LBox, LB_GETSELITEMS, 1, &sel);

Actually I think he should have just used a single selection listbox and use the LB_GETCURSEL message to get the current selection. Anyway, if it happens that your problem was that you couldn't select anything other than the first device, then this might be the reason. -- modified at 5:26 Thursday 4th May, 2006

V_shr

I looked my code , it was the correct one . and my problem isn't that I change the default device but it doesn't change , my problem is that I dont know how to change that .

Justin Tay

Reread my previous posts (I might have modified them after you read them) and tell me which part you don't understand. What do you mean by "your code was the correct one"? Setting the device just involves setting the index 'i' in the WM_CAP_DRIVE_CONNECT message.

SendMessage( hwndVideo, WM_CAP_DRIVER_CONNECT, i, 0L);

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/multimed/htm/_win32_wm_cap_driver_connect.asp[^] As I said before use capGetDriverDescription() to figure out which index your device corresponds to. -- modified at 6:21 Thursday 4th May, 2006

V_shr

I cant find similarity of our sources , and when you refer to somthing in code I cant find where you are saying . and because I didn't work on devices befor this I cant guess what are you saying. can you say it simpler ? thank you

Justin Tay

More like working with Video For Windows API in this case. Devices is too generic a term. In fact most people do this using DirectShow instead of VFW these days. My suggestion to how to get the device index that you want.

for (i=0; i<10; i++)
{
if(capGetDriverDescription(i, szDeviceName, sizeof(szDeviceName), szDeviceVersion, sizeof(szDeviceVersion)) )
{
if(strcmp(szDeviceName, "MyDeviceName") == 0)
{
SendMessage( hwndVideo, WM_CAP_DRIVER_CONNECT, i, 0L);
break;
}
}
}

Look at this to see how he enumerates the Video For Windows devices main.cpp: Line 185

int TForm1::EnumCapDrv() // enumerate the installed capture drivers

main.cpp: Line 118

SendMessage( hwndVideo, WM_CAP_DRIVER_CONNECT, sel, 0L);

main.cpp: Line 115

SendMessage( hwndSelCapDrvDlg_LBox, LB_GETSELITEMS, 1, sel);

Should be

SendMessage( hwndSelCapDrvDlg_LBox, LB_GETSELITEMS, 1, &sel);

Or it will only set the device to index 0, as sel was initialised to 0.

V_shr

I use two webcams in my project and want to switch between them without oppenning UI window . kindly ask to send the code for switching between two cameras .

Justin Tay

Does sending the WM_CAP_DRIVER_CONNECT message not work?

SendMessage(hwndVideo, WM_CAP_DRIVER_CONNECT, camIndex, 0L);

or the macro

capDriverConnect(hwndVideo, camIndex);

What problems are you facing?

V_shr

when I put camIndex , nonzero , it doesn't work , but windows recognizes both of webcams .

Justin Tay

Um. Windows recognizes both webcams as in... they both have VFW drivers? Did you see the webcams listed in the listbox of this application?

V_shr

Yes I can choose between two webcams in windows UI dialog . but as mentioned above when I put the camIndex=1 it doesn't recognize it.

Justin Tay

What windows UI dialog? Is it present in the SelCapDrvDlg in this application? Set a breakpoint in main.cpp line 199. What are the indexes of the 2 webcams you are interested in?

V_shr

it reaches the breakpoint when i=0 and it doesn't reach in i=1

Justin Tay

And there we have it. One of your webcams only has a WDM driver. You would have to write a DirectShow application.

V_shr

how can I write a DirectShow program , If you have time , please tell me . thank you

Justin Tay

If you have VC7+, download and install the latest Platform SDK. Go to http://tmhare.mvps.org/downloads.htm[^] to get the project files for the samples since Microsoft has for some reason stripped it out. Then go have a look at the PlayCap sample application in "..\Program Files\Microsoft Platform SDK\Samples\Multimedia\DirectShow\Capture\PlayCap" If you have VC6 though, you would have to grab an old DirectX SDK, maybe 2003 or 2004.