Re: OT: Why is usb data many times the cpu hog that firewire is?

Gene Heskett
2005-02-21T18:26:24Z

On Monday 21 February 2005 12:58, Oliver Neukum wrote:
>Am Montag, 21. Februar 2005 18:16 schrieb Gene Heskett:
>> Greetings;
>>
>> Motherboard is a biostar with nforce2 chipset, 2800xp cpu, gig of
>> ram.
>>
>> I've recently made the observation that while I can view 30fps
>> video from my firewire equipt movie camera with a minimal cpu hit
>> of 2-3%, but viewing the video from a webcam on a usb 1.1 circuit
>> takes 30-40% of the cpu, at half the frame rate.
>>
>> Do I have something fubar in the usb? Or is this just the nature
>> of the beast?
>
>A video stream over usb1.1 must be compressed due to bandwidth
> available. Decompression needs cpu.
>
Thats what I was afraid of, which makes using it for a motion detected
burgular alarm source considerably less than practical since the
machine must be able to do other things too. Darn. And its usb1.1
even when plugged into a 2.0 capable port.

One could probably use the FIR output of an EagleEye (X10 stuff) to
start & stop a capture, but the lag inherent in that is less than
'optimum' IMO.

Thank you Oliver.

> Regards
> Oliver

--
Cheers, Gene
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