An endless-video recording digicam?

October 29, 2005 1:56 PM

Does this device exist, and if not, how can I modify cheap consumer digicams to create it: A cheap portable digicam that will endlessly record video to some kind of small memory buffer, say enough memory for 1 minute of video, such that I could leave it running for days on the off-chance of it recording something interesting, and when something interesting happened, I just press a "Stop Recording" button, and the last 60 seconds of video are sitting in memory.

Many obvious and useful applications exist for this, so I'm surprised this isn't a higher-profile feature. In my case, I'm looking to do a home-made version of the more expensive "black-box" systems you can get for aircraft or cars - a device that records endlessly, but in case of an accident, has the crucial time period leading up to the accident recorded.

I'm aiming to build something portable that will run off 2 to 4 AA batteries for several hours or more (ie, for a bicycle - no convenient car power supply). The video doesn't need to be good (15 fps, 320x200 would be sufficient, more would be better, but battery life is also important.

The digicam info I've looked at is either inspecific about how they operate, or requires a manual delete of old footage.
The term "constant recording" in refrence to security camera features either seems to be inspecific, or mean "record until the media runs out".

As to my DIY abilities, I am very limited on programming software or firmware, but fairly capable with a soldering iron and designing simple circuits to operate more complex devices. (But if it is a suffiicently quick matter of coding, I have dev friends I might be able to persuade to help out.)

Any ideas as to where I should start?
Surely there are some cheap-ass digicams that offer this out of the box?

posted by -harlequin- to technology (13 comments total)

Why not open up a DV etc. cassette tape and set up a 60 sec loop of tape?

For example, you would loop 18.81mm * 60 sec or 112.86cm for a minute of MiniDV tape, based on this data.
posted by Rothko at 2:07 PM on October 29, 2005

You could also connect an iSight or other DV camera to a cheap iBook G3, run IVeZeen with an AppleScript that captures data to two, interchanging 60 second video files. This would meet your 15 fps, 320 x 200 requirement with pretty decent battery life.
posted by Rothko at 2:12 PM on October 29, 2005

I wish I had this for my car. Nothing is going to trump an officers' testimony except for a recording of what ACTUALLY happened.

I hear something like that *was* made for cars, but was some incredibly expensive item. The article was on slashdot, but my luck of finding it on there is zero.
posted by shepd at 2:26 PM on October 29, 2005

There are a lot of PDAs that have built in cameras. With the right software, you could do this easily. A laptop would also work, but would be much more bulky then you'd need. I've noticed PDAs have gone out of fashion lately with cell phones taking over their functionality, but while cell phones are mostly locked down, PDAs are not.

You could probably get a used one from a couple years ago. I have two that I never use (Neither of which have cameras, though). For example here is a (vintage 2003) ViewSonic V36 on ebay on ebay for a whopping $31 (so far). It has 64 megs of ram, and a 300mhz processor so I would imagine you could store a couple minutes of video in a loop. It might require some pretty hard core programming, (or maybe not) but for $31 it's pretty cheap. I'm sure there are lots of these type of things floating around out there.

A Linux powered one would be even easier to modify (the viewsonic runs WinCE)

The other problem is power consumption. I mean, you can get a camcorder that can record a few hours to tape, or you can get a laptop that can record for a few hours and then run out of batteries. With a PDA you might be able to build an external battery pack that will let it keep running for a few hours.
posted by delmoi at 2:36 PM on October 29, 2005

Professional digital video cameras are available with this type of feature. My guess is the reason it is not widely available is the cost and power consumption.
posted by MrZero at 2:46 PM on October 29, 2005

How about the Oregon Scientific ATC-1000? A self contained video camera with built in memory, plus expandable SD card slot. Runs on 4AAA batteries, and it's cheap too.
posted by jaimev at 2:47 PM on October 29, 2005

The Casio Exilim EX-Z750 camera (which does movies as well) has a 'Past Movie' mode. If you start recording a Past Movie, it actually starts some amount of time before you hit record. I'm not sure how far back it goes, but it sounds like it might possibly work for you.
posted by Malor at 2:59 PM on October 29, 2005

Power requirements need to be low, and there is no reason they can't be - a cheap digital camera draws little power (the LCD screen and writing to a flash card is what takes most of the power, and neither of those things are needed). So a digicam style approach should be able to run off a few AA batteries for a long time. CPU time (energy) for image compression is also unnecessary - RAM is cheap, and draws virtually nothing, so it can just have plenty of RAM.

The Exilim feature sounds very promising, I'll look into that. (I already have an earlier model Exilim, which I'm pretty sure doesn't have that mode, but I guess I should check out the manual Just In Case :-)

The CVS Camcorder reverse engineering project might eventually produce something useful in this respect, but I don't know much about it yet.
posted by -harlequin- at 7:53 PM on October 29, 2005

It's not cheap or portable, but you can use a Tivo to do this. Nat Friedman calls this The Retroscope.
posted by mbrubeck at 11:08 PM on October 29, 2005

I think the term for what you want is "ring buffer"

I know that various midrange digital surveilance cameras have this feature. They constantly record a buffer of images. If they receive an event notification (alarm tripped, door opened, motion detection threshold reached etc) they store images before and after the event for later review.

There is also cheap PC surveilance software for USB webcams that have the same features.

As for gettting it all in a cheap box that will run for hours on a couple AA batteries. It seems feasable, but not necessarily easy.
posted by Good Brain at 11:51 AM on October 30, 2005

MIT media lab' s wearable computer project had the Startlecam

which was a camera you wore that constantly recorded, but when your heartrate jumped or some other trigger was activated, the camera saved the image. Hopefully capturing what made you jump. It was back in 1998 but got a fair bit of publicity and some working prototypes.
posted by bluefin at 12:10 PM on October 30, 2005

I can't seem to add links, htis is to the original paper http://vismod.media.mit.edu/tech-reports/TR-468/
posted by bluefin at 12:11 PM on October 30, 2005

Recently seen on Engadget
posted by adamrice at 2:12 PM on October 30, 2005