brainwagon

The other day, I was walking around in Fry’s Electronics, and noticed that they had HP HD-2200 webcams on sale for a mere $6. I thought to myself: hey, even if the camera is crappy (and it is) that is simply too cheap to pass up, and grabbed one. Last night, I decided to try to pair it with my Raspberry Pi and the WiPi dongle, and see if I could make a simple webcam that I could move around. Over the next 30 minutes or so, this is what I came up with.

The driver for the webcam already existed. The USB driver lists the maximum power from this webcam at 200ma, which seemed modest enough, so I configured my Raspberry Pi with the WiPi and webcam plugged in directly, without any powered hub. Technically, the combination of the WiPi and the Pi might be over the reasonable limit, but I have seen others do a similar setup, so I decided to step boldly. This is nice, because it means that you just have one plug, and the resulting package is quite compact and mobile.

Experimentation using ffmpeg to read from the v4l2 device showed that the camera needed to capture a few frames before the automatic exposure would yield a decent image, so I grumbled a bit and experimented. After 10 minutes of inconsistent results, I recalled hearing about a different but simple webcam server program called fswebcam. It’s a simple little program, and was in the package repository, so a simple “sudo apt-get install fswebcam” and I had the software installed. It’s got a pretty good man page too. Fswebcam doesn’t stream video, but it can do one-shot and periodic captures, and has a lot of the essential features that I wanted, including capturing and skipping a bunch of frames, and capturing and averaging a bunch of frames for output.

This morning, I left my camera aimed at the bed in our guest room, which is where my cat Scrappy likes to take his naps. I hoped that later in the day, I’d be able to get a picture of him. The room has some direct sun during the day, which makes for some harsh lighting, which makes the picture pretty unimpressive.

Nope, he wasn’t napping there. Or was he? I loaded the image into gimp, and stretched the contrast with the Levels adjustment:

Ahah! Hiding next to the wall! (That’s a cloud painted on the wall above and to the right of him).

Pretty neat.

Oh, incidently, I didn’t have an http server installed on the Pi, but then remembered that it does have python. If you run “python -m SimpleHTTPServer” it will create a webserver that can serve files out of the current directory on port 8000.

Later, I may try to use ffserver or motion to do something fancier, but I’m happy with this setup so far.