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Registered Member #1062
Joined: Tue Oct 16 2007, 02:01AM
Location:
Posts: 1529
I have a camera module, and it outputs 60Hz Analog Composite Video. I tested this with the Yellow RCA connector on a TV, and it works great. How would I go about digitizing this? My micro-controller has an integrated ADC (Mbed), so I can stream this info to the computer. How would i go about "interpreting" this? Is there a library to take in the raw numbers and output an image?
The module also has YUV connections. There are 8 pins for the Y data, and 8 pins for the UV data. How do I actually read this? Is each pin another pixel, sent in sets of 8 pixels? Or is it something else?
I am hoping to process this on an XMOS board (XC-1A), and output Serial data for wireless transmission.
The Spec sheet for the camera module is attached. ]c3188a.pdf[/file]
Registered Member #27
Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058
Y is brightness, U and V are colour components, since the eye and brain has a lower spatial resolution for colour than brightness they save pins and space by sending the colour in lower resolution. That is why one bus is named UV, it alternates between U and V data.
The XMOS should be fast enough to capture the information in real time if you have enough RAM to store it.
All the information is in the datasheet for the sensor:
You can also grab the composite video signal if you have a fast enough A/D converter (a few MHz to get a good picture, 9 MHz for full VGA resolution). It should not take a lot of code if you know the details about video signal timing.
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
The YUV thing is a parallel bus. For each pixel it spits out 8 bits of Y (the luminance value, which is just the brightness of the pixel as an 8-bit number) and 8 bits of UV which is the colour information.
U and V are two separate colour difference signals, and it's not obvious from the datasheet how they come out of a single 8-bit port. I'd guess that they're subsampled so you get U for one pixel and V for the next. If you just want a B&W image you can use the Y port and ignore the UV.
Registered Member #2140
Joined: Tue May 26 2009, 09:16PM
Location:
Posts: 53
Ok, so was reading the datasheet, specifically page 13. This is what i got that i should do from it:
1)Wait for VSYNC to go high. This says a new image is starting. 2)Wait until HREF is high. While high, read Y data every-time PCLK goes high (or low?). Increment Y axis everytime. 3)When HREF goes low, increment the X axis. and set the Y axis to 0. 4)Repeat 2 and 3, until 1. Then update frame, reset X and Y axis.
SO:
while(1){
int x = 0;
int y = 0;
int[][] data = new int[][];
wait(VSYNC);
while(VSYNC == 0){
while(HREF){
wait(PCLK);
data[x][y] = Y.read();
y++;
}
x++;
y = 0;
}
Graphics.drawImage(data);
}
Is this right? Does this give pixel data left to right or top to bottom?
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Monochrome Composite Video
