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Connect 4 Webcams onto 1 Notebook - Bottlenecks?

Last response: in Systems
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August 12, 2012 9:52:28 AM

Hi everyone!
I'm a neuroscientist trying to set up a small platform to make video recordings of people grasping different objects on a table. To realize this, I want to connect four webcams onto one notebook that records all four streams eg. with MATLAB.

Problem: I assume not every notebook with four USB slots is able to handle four video streams at 640x480. Bottlenecks I could imagine are:

1) USB bandwidth
How many real USB controllers should the notebook have? Two should be enough, right?

2) CPU
Can notebook CPUs handle synchronous encoding of four streams nowadays or do I have to aim for a specific CPU (what about hardware-encoding)? I could also just abandon the idea of compressing the video while recording and do it later. Would that solve the problem?

3) HDD bandwidth
As I need lots of memory I cannot afford to use an SSD. Do I have to worry that the HDD is too slow?

I am very flexible on which hardware, operating system, encoding etc. to use. Are the above mentioned things actually an issue or is the task a piece of cake for an average 800$ notebook?

Thx already for your help!!

Forodin
August 13, 2012 4:16:43 AM

I have very little first-hand experience with multiple cameras on one computer (hell, the one in my laptop currently doesn't even work). Still, here's a few things I've found:

1) You'd be best off searching for home security-type setups. Many of these deal with interfacing multiple cameras to a system.

Zoneminder seems to be a relatively popular Linux-based security setup.

This article used multiple cameras hooked up to a capture card (presumably desktop-based)

This thread about framerates of multiple USB cameras on the Linux uvc developers' mailing list could provide some useful tidbits

This SuperUser question/answer reports 14Megabit usage of a single USB camera at 640x480, finding an HDD that can handle sustained 76Megabit write speeds may be challenging; however that may be doable.

If you have no further luck here, DIY-home-security-system-type forums could provide another perspective...

In any event, good luck; you're gonna need it.
August 13, 2012 6:22:15 PM

Oh thanks!! Will look into all of this. Ill probably go with Zoneminder. Using Matlab I'd have to do all the performance tweeks by hand...
August 13, 2012 6:28:39 PM

I'd definitely get to experimenting with that as soon as possible, there's a lot of specific issues that you may run into. Sorry I can't be of more help, but good luck.
!