Chapter4 Programmingwith NI-IMAQ for 1394 VIs
©NationalInstruments Corporation 4-5 NI-IMAQfor IEEE-1394 Cameras User Manual
NI-IMAQ for 1394 Acquisition Types
ThreeNI-IMAQ image acquisition types are available in LabVIEW—snap,
grab,and sequence. The following sections describe each acquisition type
and give examples.

Snap

Asnapacqui resa singl ei mage intoa m emory buffer.Use this acquisition
modeto acquire a single frame or field to a buffer. When you invoke a snap,
it initializes the device and acquires the next incoming video frame to a
buffer.Use asnap forlow-speed or single-capture applications.
Use the IMAQ1394Snap VI for snap applications. Figure 4-4 shows a
simplifiedblock diagram fo rusing I MAQ1394Snap.
Figure4-4. Acquiring an Image Using Snap

Grab

Agrabis a co ntinuous, high-speed acquisition of data to a single buffer in
hostmemory. This function p erforms an acquisition that loops continually
on one buffer. You can get a copy of the acquisition buffer by grabbing a
copy to a LabVIEW image buffer.
YoumustusetwoVIs—IMAQ1394Grab Setup and IMAQ1394G rab
Acquire—fora grab acquisition in LabVIEW. IMAQ1394 Grab Setup,
whichyou call only once, initializes the acquisition and starts capturing the
image to an internal software buffer.IMAQ1394 Grab Acquire,which
youcan call multiple times, copies the image currently stored in the internal
bufferto a LabVIEW image buffer. After the program finishes copying
images,call IMAQ1394 Close once to shut down the acquisition.