how to get current frame from camera (Video capture device)

Hi I am trying to get current frame from video capture device and I used following piece of code in my application code.

-(CVImageBufferRef) get_current_frame
{

    CVImageBufferRef buffer;
    @synchronized (self) {
        buffer  = m_curr_buffer;
        CVBufferRetain(buffer);
    }

    return buffer;  
}

But after building I am getting following ty开发者_开发技巧pe of linking error.

Undefined symbols:
  "_CVBufferRetain", referenced from:
      -[my_class get_current_frame] in my_class.o
ld: symbol(s) not found
collect2: ld returned 1 exit status

I see it's been a while since you asked this, but I wanted to post the solution for posterity. You simply need to make sure that you have the CoreVideo framework linked. That's it!