Re: [Gumstix-users] webcam image capture problems

[<48...@la...>]

I'm beginning to think that I am very lucky.  I have no trouble getting 2
or 3 captures per second with an image size of 800x600.

The latest hardware I am using is the Logitech Quickcam Laptop Pro V2.0. 
It is pricey (about $90) but it has autofocus.  Higher current draw but
for my application it is worth it....

The driver is the linux-uvc.  It provides support for many of the latest
web cams.

The software I use for image capture is motion and a modified version of
uvc_streamer (http://naaa.de/uvc_streamer.htm).  I modified uvc_streamer
to convert a motion jpeg stream to a series of jpegs that are written to
files.

I am using a Verdex XL6P and a breakout-vx with a USB hub (Targus® Super
Mini USB 2.0 4-Port Hub), an 8GB USB thumb drive (PNY--has a 4MB/sec write
speed limit), and the Logitech Quickcam Laptop Pro V2.0.  I am powering
from NiMH batteries through a couple of Anyvolt Micro regulators.  I
fabricated a USB cable with mini B on both ends and power wires attached
to the regulators--I am powering both the Verdex and the USB hub through
the USB cable.  Peak current is about 600 mA.

Note that I am capturing 800x600 color images AND writing them to a USB
thumb drive.  Thus I am using about twice the amount of bandwidth for each
image.  One important bandwidth saver here is that the Logitech Quickcam
Laptop Pro V2.0 streams motion jpeg--it does the compression.

I achieve the same capture rate with motion and uvc_streamer.

Hope this helps.

James

> Hi Christopher,
>
> I think you've showed me the way out. I've measured the USB bandwidth
> with a flash drive, it is ~850kB/sec, so this isn't a bottleneck. But
> the streaming idea you wrote is interesting, i will do some tests. By
> the way i've done some optimization in the code (and i don't write the
> image to file) and the time/image is now ~2.5 sec.
>
> Thanks for the help!
>
> Jocc
>
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