mix 2 real webcam into a fake webcam

Question

i need to get the streaming from 2 webcams on the same computer, and mix it as a fake webcam (so then i can use the fake webcam on any software). I have seen that camcamx is for mac, webcamstudio is for linux, but i need a solution for windows and i can't find it, so i was thinking to write my own small app. I can program with C#, Java and lazarus, but examples or library or whatever in any language will help anyway.

i will need to make a fake webcam that can be used as a webcam (detected on my computer as a usb webcam), and some code to grasp the stream from two real webcam and mix everything together (there will be like a primary webcam that will be bigger and a secondary webcam that will be smaller, on a corner of the big image)

Anyone can help me on that?

Answer 1

I think your question is too far out of scope for what this site is all about. You're talking about thousands and thousands of lines of code and intimate knowledge of drivers, video decoding, mixing, etc., etc. if you're going to write this software on your own.

With that said, there probably is software for this for Windows. I'd start here:

• http://alternativeto.net/software/webcamstudio/

Answer 2

This is not a trivial exercise but it can be done. I know because I've done it before. :)

I implemented this in C++.

What you need to do is to create what's known as a shared memory server. A shared memory server is a region of ram that more than one process can access. Here's how to create one using Named Shared Memory under Windows:

http://msdn.microsoft.com/en-us/library/windows/desktop/aa366551(v=vs.85).aspx

In your application that mixes the video from the two cameras, you need to create a DirectShow rendering filter (CBaseRenderer) that writes the mixed video frame into this shared memory.

On the other end, you need to create a separate Visual Studio DLL project that will implement a DirectShow capture filter (CSource and CSourceStream) that will read the video bitmaps your main application writes into this buffer. This VS project needs to be a registerable DLL that can be called to register it as a DirectShow capture device for windows.

Your main application will create and maintain this shared memory buffer when it is operating. If another application (like a video conferencing program) accesses the capture device, all that will come from the device will be a blank buffer until you main application stars feeding real video frames into it.

Tip #1: Since this is a multi-threaded operation, you will need an event handle to signal the capture filter that a frame is ready. You will also need a mutex to control access to the buffer by the "rendering" thread in your application and the "capture" thread in the capture device.

Tip #2: You won't need to call UnmapViewOfFile or CloseHandle on the memory pointers until the rendering or capture filters are disposed.

There is a lot of code you will need to grind out, so any useful examples will be beyond the scope of this discussion. This should get you going in the right direction. Good luck!

Answer 3

Capture video from real webcam: Video Capture on MSDN

Fake webcam: the well known starting point is Vivek's sample/project available at http://tmhare.mvps.org/downloads.htm, see also this post "Fake" DirectShow video capture device

Getting all together is doable, though not trivial.