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I am working on a computer vision project where I will setup a camcorder in a room at around 6am and record people as they walk around and interact with things. The recording ends at 11pm. The room itself is huge (~50 ft tall) and I need to mount the camera either on the ceiling or on one of the rafters, so I'd prefer not to have to fetch an SD card at the end of each day if at all avoidable. The people are not moving super fast, but I will be doing motion analysis based on an image of the empty room, so it's important that the video be uncompressed (compression changes pixels and messes up the before/after diff for the motion tracking). Also, the people will be interested in viewing their actions later, so it needs to be in color and preferably HD. There is likely to be minor vibrations, so it also needs to be able to stabilize the video, though I imagine that is standard nowadays.

Given those requirements, does anyone have any recommendations for a camcorder? I'm looking in the sub-$400 range if at all possible.

Edit: Compressed video is fine after all. I was misunderstanding what kind of video my test data was using, but it seems to be compressed, so I can handle that. Also, if possible I'd like the camera to be able to just stream the video to a server on a local network so I can store it offline without having to retrieve the SD card.

Edit 2: After some more looking, it does seem like there are 30M (~64ft) active USB extension cables. So it's possible that I could run a cable to a laptop on the ground and not need to worry about power or SD storage. As a result, I'm currently leaning towards an HD webcam like AJ suggested.

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Hahahahaha!!!!!! –  AJ Henderson Jul 7 '13 at 2:14

2 Answers 2

up vote 4 down vote accepted

Ok, so now that I got that comment out of my system, let me start by saying your expectation is 100% completely, totally and insanely unrealistic. HD + uncompressed = a data rate measured in gigabytes (11.2 gigabytes to be specific) per minute (16.1 terabytes per 24 hour day) and is only available on very high end cameras (>$3000, without optics) price range. Additionally, to not have to get the card every 30 minutes, let alone every day, you would need to have it wired in to a recorder elsewhere which means getting a record deck alone that will be over $600. There is simply no possible way to accomplish all of your goals within an order of magnitude of your stated target cost.

For $6,000 or so, I could probably recommend a setup that would work nicely for capture and then you'd need another $4,000 or so just for the disk drives that could store it, but unless you can bear a reasonable level of compression, then it isn't going to be any cheaper. Even SD would have problems running fully uncompressed for lengths of time without a dedicated professional deck, though SD might possibly drop the cost in to the 1 to 2k range.

While off topic for AVP, I would suggest that what you need to do is update your analysis to support compression. Add a buffer that will recognize pixels that are close in color as the same and adjust as necessary until compression artifacts aren't recognized. Unless people are all the same color as the floor, it should probably still be able to track pretty well.

You'll need this anyway as from frame to frame, there are going to be variations in what hits the sensor even if you have a fully uncompressed signal. Noise happens in the real world. You have to deal with it. The noise in the signal is going to be at least as much of a problem as most good compression, probably much more.

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Okay, fair enough. I do in fact do thresholding in my algorithm, which I've already tested on some test videos from a friend's camera. Those were around 140MB/min, so I figured maybe I could find a setup that would give me ~18 hours of video, but I assumed that was uncompressed video; if it's not, great! Also, by not wanting to get the SD card, I meant I was hoping the camcorder could have a wireless card and stream the video to a server that could store it offline. Any hope for me given that updated info? –  Wesley Tansey Jul 7 '13 at 4:47
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@WesleyTansey Have you considered just using an HD webcam with a laptop? It's probably the best bet if you have a way to secure the laptop and provide it with power. –  AJ Henderson Jul 7 '13 at 5:23
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Or raspberry pi –  Lucas Kauffman Jul 7 '13 at 10:26
    
@AJHenderson Do webcams provide video stabilization or will I need to start doing phase correlation and such on my own? –  Wesley Tansey Jul 7 '13 at 20:10
    
@WesleyTansey - I'm not aware of any, but it also brings up a question of why you expect there to be enough vibration to need it. If you are mounting it to the building, I wouldn't expect much vibration. If it is a concern, I would suggest shock mounting it. That should dampen vibration. –  AJ Henderson Jul 7 '13 at 20:50

I would recommend looking into the GoPro 3 Black Edition.

Benefits:

-US$ 400 retail price

-Wide angle lens, can cover the area you need

-4k recording, very high resolution, lets you reframe afterwards if need be.

-WiFi capabilities. I guess you could store the video signal on your laptop. I do not know what quality/compression you get out of WiFi though...

-very small and lightweight, you could basically tape it anywhere, or grip clip it.

If you need a higher quality image and less compression, I would rent a RedOne MX. With cheap optics you could get a week rental (depending on where you are) for about US$600. Then SDI the signal to a Black Magic deck (US$150 a week? maybe).

Benefits:

-"RAW" recording. It actually means the signal is compressed but not debayered in camera. If you are not familiar with the term wikipedia has a good article on it, but basically you get color information from each pixel, and not a calculated average. Dont know if you can get a white paper that describes the file structure of the RAW file so you can use it directly in your code though...

-4.5k frame size, even bigger.

-you can choose your lens, higher quality and more precise framing.

-you could tweak the frame rate. Maybe you do not need 24 fps. I would guess 8 fps is fine, if people are far away and nothing moves quickly through the frame. Some old cameraman say that to get full clarity in movement, at 24fps, an object can traverse the full horizontal frame in 7 seconds. Which means you could shoot 8fps if the fastest someone moves from one end of the frame to the other is 21 seconds.

It is a heavier camera though, a little more complicated to rig. If you can spend a little more money get the Red Scarlet X, it is much lighter, and can do up to 3:1 compression, instead of the 8:1 that the RedOne MX outputs.

Anyway, you also need to think of powering these things up, so if you can get an AC cable to the camera, you can get a USB, SDI, etc, you dont really need the WiFi capabilities...

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I hadn't thought about running a long USB cable, but that may work well with AJ's suggestion of an HD webcam. Unfortunately, this is a long term project, so renting equipment for a week isn't an option. I definitely need 24 fps, given that my current algorithm relies heavily on a steady framerate. The GoPro looks like it may be overkill, given its price (compared to an HD webcam) which seems to be mostly for features that are less applicable to my project. –  Wesley Tansey Jul 7 '13 at 20:37
    
Along these lines google key words "HD network camera". Some get pricey but there a few under $400 that have 720p but not sure about 24 fps, you should look. Streaming is the way to go, and mounting it right will make it steady. –  filzilla Jul 8 '13 at 20:14

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