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

[Paulo Marques]

Gene Heskett wrote:
> On Monday 21 February 2005 12:58, Oliver Neukum wrote:
> [...]
> > 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.

Depending on the camera model you can try some bandwidth reduction 
measures to try to make it send uncompressed video:
 - reduce frame rate. Something as low as 2 fps should be enough for 
motion detection.
 - reduce requested resolution. This of course depends on whether you 
have enough resolution or not.
 - selecting gray scale images. I don't know if your motion detection 
software is greatly affected by this, or not.

USB1.1 bandwidth is enought for 640x480, 8 bits gray scale (or color, 8 
bits bayer pattern), at 3 fps.

Of course, you can always buy a USB2.0 camera :)

--
Paulo Marques - www.grupopie.com

All that is necessary for the triumph of evil is that good men do nothing.
Edmund Burke (1729 - 1797)
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/