Grab Video Stream from FireWire

问题:

I'm trying to stream a video from a camera ( Sony HVR-Z1E ) over FireWire to my Computer. The incoming pictures/stream shall be processed further by some functions which expect the CVMat format ( from openCV ). Well my problem is now that I have no idea how to grab the stream. Okay openCV 2.1 offers me some methods ( cvCapturefromCam ) , but no matter which parameter I give him, it always gets the stream from the webcam of the laptop and not from the firewire. I heard I need to switch the primary cam in the DirectShow API ( with the Windows SDK ). But I actually don't know how to do that either. So any suggestions how to do this?

回答1:

See my related answer here. OpenCV cannot capture video from Firewire cameras natively. You will either need to use the CMU1394 driver, or the Sony driver (if an SDK is available for it) to capture video from that camera, and then pass it to OpenCV.

回答2:

Years ago, I've made something like this using DirectShow. The main limitation was fact, that image acquired via DShow was in standard PAL resolution. HD Image grabbing was not possible (it was one of the first pro-consumer HD camcorders from Sony, don't remember exact model now). Good thing was - this method didn't need anything except bare DirectShow - no additional drivers and so on. And it was VERY fast.

In general, method was something like this:

• building media render graph (of course, You have to enumerate video devices in that stage)
• inserting into it custom class which inherited from ISampleGrabberCB.

How it worked:

• it used BufferCB() virtual method from ISampleGrabberCB - which you have to write in your inherited class.
• in mentioned method, you have to leave data in global struct, and from main thread - take care of them.

I know, that's a bit fuzzy description, but I hope You'll find Your info (googling for "ISampleGrabberCB" should be a good starting point, there should be a lot of sample code).