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By Pheal
#152745
Hi, is there such a thing as a RCA Composite Video ADC to USB (Probably Pixel Data Output) Dev Board around that doesn't cost 500$+ dollars?

I am relatively new to electronics and Video ADC is out of my scope. I have people available to help me understand some concepts but I would like to continue on with my project by skipping that part for now.

I have found things like:

https://shop.maximintegrated.com/storef ... ailability

and

http://nootropicdesign.com/store/index. ... ucts_id=23

The first one, I have no idea if it does what I want it to and the second one has very low bandwidth / resolution.

I don't mind dishing out at least 150$ for this and would like to be able to build it myself from a list of parts if possible (doesn't matter much tho as long as I can use it as a solid platform).

Please advise, if there are any questions I need to answer to make it clearer do not hesitate to ask!

Specs don't matter, all I need is speed (15 fps+) and precision (as little compression as possible). Images can be handled on the board itself or piped to usb to the computer directly. I need this to do computer vision from a video signal output.

Thanks for the advice!
#152789
I'm not quite sure of what you're after. It sounds like you want a video capture device. There are lots of those availablefor a lot less than $150.

I'm not sure how the video data is streamed to the PC from such a capture device and how one would use it to do machine vision.

There's a smart guy named Hanno on the Parallax forums who uses an ADC chip to capture B&W imagesfrom a NTSC camera. I've used his method myself. It should be possible to use a red, green and blue filter in front of the a B&W camera to capture color (this is the way NASA often does color) but the frame rate will be reduced by at least one third to 10fps(from 30fps). Hanno's method uses a Propeller chip as the microcontroller.

I've collected a list of other Propeller machine vision links in post #4 of my Parallax forum index. (BTW, The Parallax forum is much more active than SparkFun's forum.)

You mention "RCA Composite Video" but that doesn't really describe the video signal you're trying to capture. If you're in the USA, I assume you want to capture NTSC video. Most of the rest of the world uses PAL.

You might have better luck if you use one of the above terms in your searches.

I've learned some about NTSC from Wikipedia and a Propeller book(here's the pdf) about the Hydra game kit.
By Pheal
#152816
Hi Duane, thanks for your reply. I am indeed looking for a video capture device. The ones that are for sale are "closed source" as in I can't modify anything from them or have access to the schematics to make my own. I know I will not really be able to perform a video capture from an NTSC signal without proper compression as the bandwidth required will be too high. I have been told by one of my friends that I will also not be able to test Video ADC chips on a breadboard since the frequency will be too high for most oscillators required and that will create noise because of the breadboard layout.

All the projects I've seen to far uses cameras and don't seem to get good "human readable" resolutions (like 720p coming from a NTSC Composite RCA cable, hell it is probably sent to a lower resolution as I found out might be 480i or 576i, but that is also ok).

I know video ADC and Computer Vision is the kind of stuff that is done as final a project, hopefully I will be able to overcome the lack of knowledge by trying hard enough and learning the bits one by one.

I will try to explain what I am trying to do a bit clearer:

NTSC Composite Signal > Goes to Video Capture / Decoder Board > Builds an image on board > Processes the images with algorithms on board to reduce the bandwidth required to send to PC afterwards by USB (kind of dumbs the image down with an algo I made) > PC does another round of processing on the image

This is VERY close to what I am trying to achieve but it uses a camera instead of a NTSC Composite RCA signal and is slower:

http://forums.parallax.com/showthread.p ... NTSC-Video

How easier does it get if I only need a B/W image instead of color? How would I go to have a higher resolution image and output speed out of a similar circuit?

I don't need a complete solution as this topic is kind of complicated and I know I have lots of learning and searching to do on this, but pointing in the right direction always help =).

Thanks for all the input, it has greatly help so far. I will post back when I get more stuff figured out and will keep looking here if anyone has other awesome knowledge to share.

PS: I had already looked at propeller chips before but I tought I had to program using their language... Apparently there are tools to stay in C, which makes them way more appealing now.