Acquiring video from multiple USB cameras

[carlover]

Hi,

I have three USB cameras and have to acquire, display, and save video. I do have an option to synchronize and process video 'offline' (it would be nice if it is in real time but not a requirement). It's on LV 8.5, Video Acq. 8.5.1, and I have image dev toolkit. My question is two part:

- is there a way to simultaneously acquire from three USB cameras?

- what's the best method to synchronize video from multiple usb cameras?

I can acquire video from only one camera at a time. While I am aware of NI saying that IMAQ can only handle one USB camera at a time, is there a way around this?

Is it possible to build and simultaneously run three standalone exe apps to acquire video on one machine (haven't try this one yet but I have feeling that it might not work).

Is anyone aware of other toolkits on the market that allow multiple usb video acq. for LabView?

I guess as a last resort I could have one computer per camera (boy will my VP first laugh at me for prising LabView and NI, and afterwards I am not sure what he will do ) , but that brings question of best method to synchronize video regardless of where/how video is acquired.

Thanks a lot

[Tim_S]

QUOTE (carlover @ Mar 12 2008, 12:17 PM)

- is there a way to simultaneously acquire from three USB cameras?

If NI is telling you that the driver can only acquire from one camera at a time, then the only way to acquire from more than one camera at a time would be to change drivers. This would include using multiple applications as the driver would be common the all of the applications.

From my understanding of LabVIEW and vision, I would say the issue wasn't the choice of LabVIEW/NI, but the choice of using a USB camera system and the limitations that supplies.

For the synchonization part, that depends on what you mean by synchonization.

Tim

[Neville D]

Why don't you migrate to firewire cameras with a firewire card in your PC? That should solve your problem, and firewire cameras have better resolution, triggering and speed. You can get cheaper ones too.

Neville.

[carlover]

QUOTE

For the synchonization part, that depends on what you mean by synchonization.

I mean time synchronization - where I would have the ability to watch videos from all three cameras, and all cameras would show their prospective views at the same time frame of reference.

One way is to time stamp frames using computers clock. I was wondering if there is a better/more elegant way to do so (remember cameras are usb and don't have common trigger)

QUOTE (Neville D @ Mar 13 2008, 12:16 AM)

Why don't you migrate to firewire cameras with a firewire card in your PC? That should solve your problem, and firewire cameras have better resolution, triggering and speed. You can get cheaper ones too.

Neville.

That would be nice but I don't think it's an option now. I would love to have NI (or other) video card and connect cameras to it - most of my problems would be done with.

So any other ideas of how to use three usb cameras with LV and how to time sync video frames?

Thanks

[tmot]

QUOTE (Neville D @ Mar 13 2008, 01:16 AM)

Why don't you migrate to firewire cameras with a firewire card in your PC? That should solve your problem, and firewire cameras have better resolution, triggering and speed. You can get cheaper ones too.

Neville.

Hi!

What FW-cameras do you recommend that are cheap? I have been having the same problems and I am thinking about switching to firewire instead of USB.

Regards

Mattias

[crelf]

QUOTE (tmot @ Apr 7 2008, 10:38 AM)

What FW-cameras do you recommend that are cheap?

I pretty-much exclusively use http://www.alliedvisiontec.com/' rel='nofollow' target="_blank">Allied Vision Technologies firewire cameras. They're, of course, not as cheap as Logitech webcams, but you get what you pay for.

[Neville D]

QUOTE (tmot @ Apr 7 2008, 07:38 AM)

Hi!

What FW-cameras do you recommend that are cheap? I have been having the same problems and I am thinking about switching to firewire instead of USB.

Regards

Mattias

Depends on the specs you have ie. color? resolution? CCD size (2/3" 1/2" etc), frame rate ?

I have had good experience with Prosilica and Basler cameras. In terms of price, most camera vendors are competitive and in the end it boils down to service and support.

In my experience SONY cameras have the weakest mechanical design (though many other brands use Sony CCD's on the inside). I have seen many failures of SONY cameras when mounted in harsh environments.

You don't need a frame-grabber with FW cameras, just a firewire card in your PC (around $40 to $100 at most) sometimes already built-in the PC.

Don't forget to factor in the cost of a good lens ($100 to $500 if very special requirements).

Ask if you need lens info too.

Hope this helps

Neville.

[tmot]

QUOTE (Neville D @ Apr 7 2008, 06:21 PM)

Don't forget to factor in the cost of a good lens ($100 to $500 if very special requirements).

Ask if you need lens info too.

Hope this helps

Neville.

Thank you for your good reply. I realize that I didnt describe my problem good enough, sorry for that.

I would like to use two cameras for monitoring of a robotized laser welding cell. The distance is about 3-4 meters and I want the picture in colour, with good resolution at a pace of ~25 frames/second.

I have worked with Basler cameras before and find them good enough for my purpose. The problem is that I'm not very good at lenses - I need to look into this more.

Could you recommend some good readings about lenses?

Thanks in advance.

/Mattias

[crelf]

QUOTE (Neville D @ Apr 7 2008, 12:21 PM)

You don't need a frame-grabber with FW cameras, just a firewire card in your PC (around $40 to $100 at most) sometimes already built-in the PC.

That's right, although you do need to buy a license for the IEEE-1394 IMAQ toolkit (as far as I remember, it comes free with NI firewire cards).

QUOTE (tmot @ Apr 7 2008, 01:08 PM)

Could you recommend some good readings about lenses?

Try this

I usually talk to my camera/lens vendor about lenses - working out the simple stuff based on the FOV and WD is pretty straight forward, but the vendor will know all the little idiosyncrasies that could ruin a simple project.

[Neville D]

QUOTE (tmot @ Apr 7 2008, 10:08 AM)

Could you recommend some good readings about lenses?

Thanks in advance.

/Mattias

See Navitar Lens selection Wizard

Keyence has a download on their website entitled "Helpful tips for Machine Vision Solutions Lens Selection Guide"

Attached is a short technical reference from Fujinon. I have found it quite useful.

Some brief pts:

1 Choose "megapixel" or "machine vision" lenses. They are usually of better quality (and more expensive)! CCTV lenses are not that great.

2 C-mount lenses are usually better quality than CS-mount. Most machine vision cameras will have a C-mount anyway (but you can order CS mount).

3 Auto-focus or auto-zoom lenses are good ONLY for clean, lab-type environments are not to be used in an industrial 24-7 operation. The motorized mechanisms usually fail after a while.

4 Choose lenses with lock screws on the manual adjustments.

5 Choose lenses with large aperture (small f/number). They will allow more light into the camera, i.e. are "brighter" but will usually have more lens elements and be correspondingly heavier and more expensive; don't use large aperture if depth of field is important (usually isn't for machine vision apps).

6 Always place the subject to be photographed at the centre of the lens. That is the area with the least chromatic aberration and distortion.

7 Make sure subject plane is parallel to the plane of the lens.

8 Experiment with lighting to get the best angles; more light available, the better, you can always decrease shutter speed.

9 I have used Tamron, Fujinon and Pentax lenses. All are excellent quality and reasonably priced. Lenses from Edmund Optics, Schneider and Lynos are good too, but haven't used them.

10 Lead times on some esoteric lenses can be quite long. Check with your supplier first before ordering.

Neville.

[crelf]

QUOTE (Neville D @ Apr 7 2008, 01:50 PM)

Some brief pts...

That's a really good starting list Neville :thumbup:

[B Grey]

QUOTE (tmot @ Apr 7 2008, 10:38 AM)

What FW-cameras do you recommend that are cheap?

I find http://www.theimagingsource.com/en/products/cameras/' rel='nofollow' target="_blank">The Imaging Source to be a good source of inexpensive Firewire cameras. Of course, one should always bear in mind the price-performance relationship!

B

[Irene_he]

QUOTE (carlover @ Mar 12 2008, 10:22 PM)

So any other ideas of how to use three usb cameras with LV and how to time sync video frames?

Thanks

Hello, with IVision LabVIEW toolkit, you can record multiple video streams from multiple USB cameras into one AVI file and you can play back later to see the multiple videos. More, you can combine the multiple video streams to different display mode, such as picture in picture, side by side etc. There are examples in IVision LabVIEW toolkit to get you started easily. Demo version is free to download. Below is the link:

http://www.hytekautomation.com/Products/IVision.html

Irene