Multi Camera Acquisition (IMAQdx)

[petitOhu]

Hi,

I failed grabbing two cameras with the IMAQdx driver. As an example, I get the "Grab and Select Mode.vi" exemple, copy and paste a second loop for my second camera (see attached exemple).

But the second call to "IMAQdx Grab.vi" return an error :

"L'erreur -1074360296 s'est produite à : IMAQdx Configure Acquisition.vi
Raisons possibles :
NI-IMAQdx: (Hex 0xBFF69018) Insufficient transfer engine resources."

Sorry about this question of beginner, but does someone can help ?

Thanks a lot.

PS: I did not suffer from this problem with "IMAQ for 1394" driver, but it is not supported anymore... I upgraded Vision Acquisition Software to version VASAugust2010, don't know if my problem is caused by this upgrade.

PetitOhu

[petitOhu]

More information : my problem depends on the "Video Mode" I select. On 7.5fps or less, there is no bug. For 15fps modes, error occurs as described above.

I am a little bit surprised. Indeed, I work with 8 bits per pixels, in a 1280x960 pixels format.

So one image = 1280x960x8bits = 8Mb

At 15 fps, 8x15Mbps = 120Mbps

With 2 cameras, 240Mbps : the limit of 400Mbps seems to be far superior...

Do you think it is still my problem ?

NB : I work on windows xp service pack 3, and I have install the "prosilica" patch to break the limitation of 100Mbps for my firewire bus.

[GuenterMueller · Accepted solution]

Should be a bandwidth issue and you might have to decrease the packet size.
By searching the NI Support with the term "Insufficient transfer engine resources" you will find lots of (hopefully good) threads.
If not, let us know here.
Guenter

[petitOhu]

Thank you for your answer.

You are right, it seems to be a problem of packet size. The Camera Bandwidth Table on this page give some explanations. But I am still disappointed by the fact that in some cases, the real bandwidth is greatly less than 400Mbps...

[GuenterMueller]

This will put some light on how cameras operate on the 1394 bus. Look at "Isochronous Transfer".

Regards, Guenter

[petitOhu]

Thank you, Guenter.

I understand the differences between asynchronous and isochronous data transfers, but I can not find how choose or configure this mode with IMAQdx driver. Have I misunderstood something ? (Sorry if my question is stupid or if I miss an obvious standard setting).

[GuenterMueller]

In the same document you can find about DCAM: "It also specifies that the isochronous protocol be used for digital video transmission. The isochronous protocol is appropriate for video because the camera can be guaranteed its required bandwidth."  This means, that you have to live with reduced packet sizes.

Alternatively you can add another 1394 interface to your computer in order to achieve maximum frame rates for each camera.