Frame Grabbing

The term frame grabbing describes the method that is used for capturing an image from the imaging device, including all transport and protocol issues. Figure 3.1 shows the relevant subjects.

Figure 3.1. Getting an Image into a PC


In general, we discuss the following items:

  • the camera itself (or another imaging device, such as an ultrasound imager );
  • the transfer from the imaging device to the PC, including physical (cable) and protocol aspects;
  • the power supply of the imaging device ( especially of interest if small cameras are used);
  • the frame grabbing device inside the PC; mostly a plug-in PC card;
  • if possible, the camera control functions, which can be sent directly from the PC.

Table 3.1 describes some examples.

Table 3.1. Frame Grabbing Methods


IEEE 1394


Camera Link


Imaging device:





Transfer protocol:

1394 camera

USB camera

Camera Link

analog video

Frame grabber:

1394 PCI

USB controller

CL video

analog FG

Power supply:

bus cable

bus cable




1394 serial

USB serial

CL parallel

analog video

The three digital transfer methods are discussed later in this chapter. Figure 3.2 shows a typical block diagram of a PCI frame grabber card. The card offers multiple video input possibilities, in-detail S-video, and composite signals. In the top row of blocks the separation of the luminance and chrominance signals into a HSL color model is clearly visible.

Figure 3.2. Typical Block Diagram of a PCI Frame Grabber


After some adjusting, filtering, and scaling, the signal is formed to a YC b C r model with the possibility of 4:2:2 or 4:1:1 color subsampling. The lower area of the block diagram describes the interfacing with the PC, in this case, via a PCI bus connector. Other possible interfacing standards are CompactPCI or PC104.

Camera Interfaces and Protocols

Image Processing with LabVIEW and IMAQ Vision
Image Processing with LabVIEW and IMAQ Vision
ISBN: 0130474150
EAN: 2147483647
Year: 2005
Pages: 55
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