Analog Composite Video Acquisition and Data Synchronization

[jch303]

WinXP, LabVIEW 7.1

New to using LabVIEW and need help choosing the right hardware.

For our experiments, we have an analog composite video source which we need to acquire and at the same time, acquire a number of voltage signals at different sampling rates that needs to be synchronized with the video data.

We would like to keep with using a Laptop computer (high-end) so there is some portability.

To acquire the composite video into the laptop, what hardware is necessary?

To acquire the voltage signals at different sampling rates into the laptop, what hardware is necessary?

Are there examples on how to synchronize voltage data (or signal data in general) with video data?

Future thanks for any assistance.

[Dan_Quinn]

Hi jch303,

Thanks for using our discussion forums! There are a few things you might want to try here.

First of all, if you really want to stick with the laptop, the Data Acquisition should be pretty easy to put together- we have quite a few different models of PCMCIA DAQ devices. I'm not sure how many channels you need or what resolution or sampling speed you need though. Here is a link to our DAQ devices, and if you provide some specs, I'd be glad to recommend one:
http://sine.ni.com/apps/we/nioc.vp?cid=13873〈=US

With regards to the analog image acquisition, this is the tricky part. Unfortunately, we don't offer any analog image acquisition devices for laptops. If you are looking to acquire images on a laptop, you might want to consider using an IEEE 1394 (firewire) camera instead of analog.

Another option that would be quite easy to integrate would be to use a PXI chassis instead of a laptop. In this case, you could simply buy a small 4 slot chassis with a controller, analog IMAQ module and M-Series DAQ module. Synchronization would be very easy and the PXI chassis would be smaller than a full sized PC.

Let us know if there's anything else we can help with.

Regards

Dan
National Instruments

[jch303]

Thank you for the quick response, I have been discussing for a while now with our team and we have determined the following:

- We will need to use a laptop for data acquisition
- We will be now using a 1394 Firewire Video Source that we need to capture video data
- We may be running up to 10 channels of data that needs to be sampled at about 8 kHz. If necessary we can keep it down to 5 channels.
- One channel will be sampled at about 1 kHz.
- All channels will be analog voltage signals.
- Resolution wise, the best is preferred.

So we may need up to 11 channels, but we can keep it down to 6 channels if there is no way around it.

Our concerns involve the amount of data coming in and out at once (possible 11 channels, large sampling rates, along with video capturing, and instrument control through LabVIEW). With all we want to do, we are afraid computer system resources may be bogged down.

Do the Data Acquisition Devices contain a buffer so that data can be recorded on the unit itself and periodically writes the information to the computer? Or does all the data get written to the computer immediately?

In addition, with data being recorded at different sampling rates (8 Khz, 1 kHz, and 30 frames/sec video), how does one go about synchronizing all the data so it actually makes sense when we analyze it?

[mhaag]

Thank you for getting back with us. If have decided to use a laptop and then investigate the use of a FireWire (IEEE-1394) camera, then there are a few key things to understand for the video side of your application. The 1394 standard has two versions, 1394a and 1394b, which have maximum transfer rates of 400 Mbit/s and 800 Mbit/s. You can find a brief overview of these standards on our website:

http://zone.ni.com/devzone/nidzgloss.nsf/webmain/9ACCAB3D225B3C298625686A00793D53

Acquiring from a single frame at 30 fps should not be a problem as far as bandwidth and throughput goes.

Now in regards to the data acquisition side of your application, you may want to post those specific questions, especially regarding the synchronization on the DAQ forums since they will be more current with their DAQ knowledge then us in the IMAQ team. As mentioned earlier, we have a number of PCMCIA and USB data acquisition products that you can use. We have PCMCIA boards that can acquire at 200 kS/s or 500 kS/s, which is more than enough to acquire 10 channels at 8 kHz each. These boards will accept 16 single-ended inputs or 8 differential inputs.

The synchronization may be a little more challenging in order to have various sample rates. One thing you can always do is just sample all at 8 kHz and then just ignore/erase the data in the channel that you do not need to monitor as frequently. If you have any more questions on the IMAQ please let us know; otherwise, while I would be more than happy to help, I would recommend posting on the DAQ forums if you would like more details on that side of your application.

Regards,
Michael
Applications Engineer
National Instruments

[jch303]

Now if I understand correctly. The standard DV firewire video output does NOT work with NI-IMAQ, correct? (as in a DV camcorder)

We have an analog video signal that we will be using a D/A converter to convert into Firewire DV. A product like this (link below), if I am correct, won't work with NI-IMAQ since I am assuming "DV output" is compressed video.

http://www.datavideo.us/products/dac_100_main_page.htm

However, I did find an analog to digital converter that outputs "uncompressed" digital output via firewire here:

http://www.1394imaging.com/products/interfaces/dfg13941/

Would that work to take an analog source, convert into "uncompressed" digital, then use 1394 on the laptop to acquire the signal?

FINALLY, to possibly make it easier, if we were using a desktop instead, is there something I can use to acquire that analog signal directly in to LabVIEW?

[ColinAE]

Hello.

The test for whether it is compatible with our NI-IMAQ for 1394 driver is that the camera is DCAM compliant:

KnowledgeBase 1V9EHSU9

I was unable to verify from the page you linked whether it was or not for sure.

If you have standard analog video data, then a desktop would be a much simpler solution, as you could use one of our analog boards to directly feed data into your LabVIEW application. Depending on whether it is color or monochrome, you would use the PCI-1409 or the PCI-1411.

Feel free to call our sales force for clarifications on this issue as well, they will definitely be able to help you out with this selection!
Regards,
Colin C.
Applications Engineering