Grabbing modified video ..

That may be a misleading header ..
I contemplate a project where it would be desirable to grab part of the video-screen (a central line) and not the whole format. Grabbing full-screen video is notoriously slow, so I wonder if I can just grab one central line and transmit that for further processing? The general idea is to use the video-camera as a light-sensor and then I'll attempt to process the spectral input at the next stage ..

CarstenT

Sure, no problem. Once you have got the video to a PC, you can separate out whatever parts you want and do whatever analysis you need.

If you were going to do this on an Arduino instead, you could see what the video experimenters shield does for you, but I think it's quite limited in its capabilities.

I've seen some really basic serial cameras. You could read the first line only, straight into the arduino. Check the ArduCam project. They have a list of camera models that have worked with arduino.

Hi PeterH & pYro_65

Thanks for your input.
Peter, I don't think that your suggestion would pose a problem for me.
pYro_65, as far as I can tell, I'll have to have a look at the firmware for arducam ..
I took a look around for a linear cmos .. and they are quite ordinary.
http://www.hamamatsu.com/jp/en/product/alpha/C/4119/S8378-1024Q/index.html
I didn't tell you about the front-section of my project: I would like some simple (point) light input, let it go through a prism to separate the color-frequencies (-> linear light source) and have some camera or cmos catch it. That's quite ambitious, but we are talking about how viable the project is here, right.

It was inspiring to read about the arducam projects.

CarstenT

if I can just grab one central line and transmit that for further processing?

Well for a 625 line system:-
If it is a horizontal line then that would require an A/D converter capable of a sample rate of 5MHz and depending on the resolution transfer all those samples into the arduino in 64uS.

If it is a vertical line you can take one sample per line scan, therefore you would need to have the A/D converter to sample at a rate of 64uS but you would need a fast sample an hold in front of it.

Grumpy_Mike:

if I can just grab one central line and transmit that for further processing?

Well for a 625 line system:-
If it is a horizontal line then that would require an A/D converter capable of a sample rate of 5MHz and depending on the resolution transfer all those samples into the arduino in 64uS.

If it is a vertical line you can take one sample per line scan, therefore you would need to have the A/D converter to sample at a rate of 64uS but you would need a fast sample an hold in front of it.

Hi Grumpy_Mike
On this project I have a long way to go. I have no clue of what the signal would look like in a cable .. anyway, I think that you refer to some screen-size group of pixels. If you follow the link I popped above you'll find a linear cmos .. probably used for scanning barcode-lines, but I don't know. It snaps 1024 pixels on one row - end of story. It operates at a clock-frequency of 500 kHz, but I'll have to spent some time on what sort of signal is comming and how & where I can catch it. It works on 5v so the 4 pins 'smells' of usb. So far I've only worked with serial communication.
I googled on "64uS" and got a converter-cable .. was that intended?
Arduino has this forum-subset of questions about viability of projects, that's why I ask here, but I'll probably use a Raspberry Pi for the project. It certainly has some video-features and both RCA and HDMI interface for output. Anyway - the snag is lying before the signal is sent. Playing with firmware for cmos's is probably not for newbies, but the lines-scanner (as I call it) seems to be what I need.

Yes nice sensor, who stocks them? Not any of the majors I checked.

However, I don't think a linear CCD sensor counts as video in my book, it is just a row of sensors.

If you have a composite video signal this is what you need to read in a vertical line.
Imgur
Done a long time ago.
This used a linear CCD to measure the size of coins:-
Imgur
It shows you how easy it is to drive that sort of thing.