User`s guide

Previewing Data
• “Performing C ustom Processing of Previewed Data” on page 2-13
Opening a Video Preview Window
To open a Video Preview window, use the p review function. The Video
Preview window displays the live video stream from the device. You can only
open one preview w indow per device. If multiple devices are used, you can
open multiple p r eview windows at the same time.
The following example creates a video inputobjectandthenopensaVideo
Preview w indow for the v ideo input object.
vid = videoinput('win video');
preview(vid);
The following fig ure show s the Video Pre view window created by this
example. The Video Preview window displays the live video stream. The size
of the preview image is determined by the value of the video input object’s
ROIPosition property. The Video Preview wind ow disp lays the video da ta at
100% magnification (one screen pixel represents one image pixel).
In addition to the preview image, the Video Preview w indow includes
information about the image, such as the timestamp of the video frame, the
video resolution, and the current status of the video input object.
Note Beca use vi deo formats typically expr ess res ol uti on as wid th -by-heigh t,
the Video Preview window expresses the size of the image frame as
column-by-row, rather than the standard M ATLAB row-by -col u m n form at.
2-9