User manual

Small Vision System User Manual 15
Only one type of device, the MEGA-D or Dual DCAMs, will be seen by the smallv program. The
choice depends on which interface library has been loaded (see Section 2.1.3). It is possible to mix these
devices on the same IEEE 1394 bus, but a given application will see only one type of device or the other.
Analog Stereo Devices (STH-V3 and user cameras)
Analog camera input goes through an analog framegrabber , where it is converted into digital form
and sent to the host computer memory. The smallv interface will input video from the cameras through
either one or two framegrabbers, depending on the type of setup. There are three choices:
1. Line interlace [default]. This is the mode for the STH-V3 line interlace stereo head. Any
framegrabber can be used in this mode.
2. Dual framegrabbers. This mode uses two framegrabbers, with one framegrabber per camera.
Check Table 2-1 for supported framegrabbers.
3. RG components. This mode uses the Matrox Meteor RGB or Meteor II, and inputs one
camera video stream on the R channel, and one on the G channel.
It is important for stereo processing to have the left camera image appear as the left image in the
smallv program. Once the video input is displayed, you can check this by pointing the cameras along
your line of sight. The right camera appears on your right side, and the right image on the smallv
display should show this image. You can cover one camera with your hand, and observe which displayed
image goes dark. With dual framegrabbers or RG input, the solution to having the wrong camera inputs
is to simply switch the inputs, or to use the swap button in smallv, which interchanges the images in
memory.
Under line interlace mode (Figure 2-3), the first horizontal line of a video field is from the left
camera, the second from the right, the third from the left, and so on, making a single video stream. The
SVS software de-interlaces the video stream, reconstructing the left and right images in memory, at half
the original vertical resolution. Because of the variation in how framegrabbers determine which is the
first line of a field, the SVS software will sometimes switch the left and right fields during de-interlacing.
The swap button switches the left and right fields during deinterlacing.
The smallv application interfaces only to one analog stereo head, using the first one or two
framegrabbers that it finds. It is possible to specify other framegrabbers from a use application, using the
SVS API.
2.1.5 Frame Size
The SVS libraries as delivered can work with frame sizes up to 1288 by 1032. In fact, the SVS
algorithms can work with arbitrarily sized frames.
Single
video
stream
Left camera
field
Right
camera field
Interlaced
field
Figure 2-3 Line-interlaced stereo cameras (STH-V3 stereo head). Alternate
lines from each camera are interlaced into a single video stream.