Using mm_Capture() to take an image from a video call

Hi,

I am trying to use mm_Capture() to take a photo from a SIP call. I am performing the following steps:

1. Opening two ip media devices and the multimedia device
2. Using dev_PortConnect() to establish a full duplex audio/video connection between the two ip media devices
3. Using dev_PortConnect() to have the multimedia device receive-only video from one of the media devices
4. Starting the IP Media streams
5. Calling mm_Capture() to grab an image

mm_Capture() creates a 0 byte file and then returns a MMEV_CAPTURE_FAIL event. Output from mm_ResultInfo() is this:

mmValue = 0x1
mmMsg = System error
additionalInfo =

The documentation mentions using mm_Pause() and mm_Resume() to pause and restart the media (apparently when capturing from video playback), but I have tried this and pausing fails (because the media device is technically still idle?).

Is what I am doing possible?

Thanks,

Brendan