Acquiring and buffering a video signal without additional software

[mikie_121]

Hi

I have a generic USB capture box to which I am inputting an RCA video signal only (no sound).

Am I able to display the video feed in Labview and continuously buffer 30 seconds of it?

The idea is that when an input trigger fires the buffered video is saved and the live stream continues to save another 30 seconds. Once the trigger has been fired the video does not need to be displayed. When the recording is finished the program continues to monitor and wait for another input.

I have been told that activex will work, but I don't have any idea how to implement it.

I am using Labview 8.0 and as this is at University I don't have access to any labview plugins.

Any help will be very greatly appreciated.

Mike

[VuD]

Hi Mike,

Thanks for using our discussion forums.  In regards to your USB device, we do offer an NI IMAQ driver for USB.  Though it is not supported by our application engineers, this will allow you to perform very basic image acquisition with your camera.   

If you are able to use our Vision products in the future, a simple way to save a buffered video in LabVIEW is just to build an array of images until you reach 30 seconds (you can calculate this based on your frames/sec rate).   In a case structure, we can subset the most recent items into a sub array and save that to file depending on the data type.  In regards to triggering, we can software trigger this configuration using another case structure in the while loop so that when it fires the “buffered” image video will be saved.  

If you would like to use ActiveX you can learn more about this application with LabVIEW at our Developer Zone tutorial https://www.ni.com/en/shop/labview/activex-and-labview.html  .  I hope this gives you a good start.

Regards,

Vu Doan
Applications Engineer
National Instruments

[mikie_121]

Hi Vu

Thanks for info.

The free NI IMAQ looks good, but the system requirements state:

'LabVIEW 7.0 or higher with NI Vision 7.1 or higher for the USB LabVIEW support. '

Do I need to get this and does it cost?

Thanks

Mike

PS. How big is the ni_imaq_for_usb.zip file? I only have a limited download quota at uni and I can't find a size on the page.

Message Edited by mikie_121 on 11-01-2006 07:34 PM

[RavensFan]

Hello Mikie,

I began a download.  The zip file appears to be 2.93 MB.

[mikie_121]

cheers ravens fan.

the help file in the zip looks really good.

thanks

Mike

[VuD]

Hi Mike,

The answer to your question as well as some good follow up info regarding USB devices with IMAQ Driver/Vision products are actually discussed in another forum http://forums.ni.com/ni/board/message?board.id=200&message.id=9409&requireLogin=False

Take a look at DJ L.'s comments in particular.  Hope this helps.

Regards,

Vu D.

[mikie_121]

Hi

I have managed to view and record video using IVision Labview Toolkit 1.8. However I must write my own vi and not use someone else's. I know that the toolkit uses directshow (which has limited functions compared to activex, but I'm not doing much with the video anyway) and I would like to know how to write my own vi to use directshow and capture frames. The vi's from the toolkit are password protected.

I have decided to use directshow because the ni_imaq for usb.zip needs additional software which isn't an option for me.

Once again thanks in advance for any info

Mike

[MattP]

Hi Mike,

LabVIEW can provide interfaces to external DLL's, .NET Objects, and ActiveX Controls/Interfaces using our connectivity VI's, though the implementation details on how to use the methods exposed by these interfaces isn't something I can help you with directly.  Your primary source of information will be the MSDN Documentation for DirectShow, and you might also consider cross-posting in AV/DirectShow specific forums for more detailed implementation assistance.

[mikie_121]

Hi MattP

Thanks for the link, there is so much info. Now to start reading...

Mike

[mikie_121]

Thanks all who helped. I managed to get the program working well with the IVIsion Toolkit 1.8. I put the frame snapshot vi in a loop which runs continuously naming files according to the loop iteration and deleting 15 images behind.

Thanks
Mike