User manual

Small Vision System User Manual 16
Video Format Frame Sizes
Line interlace 160x120
320x120
Dual framegrabber 640x240
and RG component 320x240
320x120
160x120
1394 (digital) interface 1280x960, 640x480, all
others above
Table 2-3 Frame sizes available for video input
in smallv.
Video frame size is selected with the Size drop list in the Source area. Video size can be changed
only when frames are not being acquired. Once acquisition starts, the frame size is fixed.
2.1.6 Image Sampling
The sampling for analog framegrabbers is implicit in the frame size. For example, if the camera image
size is 320x240, and the requested frame size is 160x120, then the full image is scaled down by the
framegrabber, usually using interpolation to produce a smooth image.
With the MEGA-D digital interface, the user has full control over the sampling method, and the
Sample and Size controls combine to produce the final result. For example, if the sampling mode is x1
(no subsampling), then and image size of 320x240 produces a subwindow within the full image.
(Subwindowing is not available from analog framegrabbers supported by SVS.) The placement of the
subwindow can be changed in real time under program control, using the dialog from the Subwindow…
menu.
There are several sampling modes. Decimation samples the image by removing pixels, e.g., “x2
dec” means that every second pixel in a line is removed, and every other line is removed. Binning
samples the image by averaging over a block of four pixels, to produce the same result. Binning produces
smoother images with less noise, but it is slower than decimation, which is done by the stereo hardware.
Combination sampling modes are available, e.g., “x4 bin+dec” samples the image down to ¼ size in
horizontal and vertical directions, by decimating by 2 and then binning by 2.
The Dual DCAM stereo device supports a single sampling mode, x2 binning at 320x240 output
resolution. The binning mode will reduce video noise for this device.
2.1.7 Image Source
The source for stereo images can be either a memory buffer or a live video stream. The Source
drop list lets you choose between these, or to stop any input. Buffer input is discussed in Section 2.1.9.
2.1.8 Streaming Mode
Images from video cameras or the buffer can be processed in three acquisition modes. Only one
acquisition mode is active at a given time.
• Continuous mode. In this mode, stereo pairs are continuously input, processed, and displayed.
The maximum frame rate is 30 Hz for live analog image data, and up to 80 Hz for the MEGA-
D digital system. See Section 3.7 for performance information. The rate is indicated next to
the text information area.
• Single frame mode. In this mode, a single stereo pair is input, processed, and displayed each
time the Single button is pressed.
• Freeze mode. In this mode, a single stereo pair is input, then the same frame is continuously
processed and displayed. This mode is useful in checking the effect of different stereo
parameters on the same image.