Need Advise: How to Analyze Video Input
Mavromatis
Posts: 5
Hi there,
I'm trying to figure out the easiest way to analyze a composite video input. I'm trying to get my screen masking controller to automatically detect if the video is 16x9 or 4:3, etc. Any ideas?
Video:
www.mavromatic.com/archives/000670
Blog Post:
www.mavromatic.com/archives/000563
Thanks,
Danny
I'm trying to figure out the easiest way to analyze a composite video input. I'm trying to get my screen masking controller to automatically detect if the video is 16x9 or 4:3, etc. Any ideas?
Video:
www.mavromatic.com/archives/000670
Blog Post:
www.mavromatic.com/archives/000563
Thanks,
Danny
Comments
Edit: Have a look at the Propeller Counters application note at parallax's doc page
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Paul Baker
Propeller Applications Engineer
Parallax, Inc.
I see that EL1883 will give my HSYNC and VSYNC. So I can count the lines... how would I go about checking the lines content to see if the line is black?
I have done a SDI mod to my DVD player using a SDI encoder from the 8 data lines + H/V sync + CLK and an FPGA (verilog). I would like to stay away from such a project since it required a lot of time and circuits to get it to work. www.mavromatic.com/archives/000029
I could use a PC and a video input card and run software to analyze the video but I would like an embedded device to do it...
Danny
Post Edited (Mavromatis) : 4/12/2008 5:00:12 AM GMT
wait for H-SYNC
pause for the time it takes NTSC to run through like 5-10 lines
test next few lines for black level with an ADC to determine if the screen has black bars or not
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E3 = Thought
http://folding.stanford.edu/·- Donating some CPU/GPU downtime just might lead to a cure for cancer! My team stats.
I really need to know if its 1.85:1, 2.35:1, etc. not just if it's 4:3 or 16x9. So I would need to know what type of letterboxing is happening. What parts would I need to make this work?
Thanks,
Danny
I did something similar to this with a PIC a few years ago. I used an EL1881 sync separator to trigger an interrupt on the composite sync output that would run take 6 ADC samples on the video line. I stored this data in an array that I processed outside the interrupt routine. Your situation can just increment a 'black line' counter instead of storing in an array.
As for an explanation on how the EL1881/EL1883 chips work: The composite sync output contains both vertical and horizontal sync information. It signals every new video line, and every time the frame goes back to the top. Using the sync chip is perfect for this situation because it means you'll know exactly which video line you are on. No need to guess which line you are on with messy delay routines.
Sweet, sounds like that is my solution. Yes, I only need to know the top bar height (since the bottom is the same). If there is no letterboxing, I know it's 4:3, so I could trigger a side masking.
So the EL1881 chip will signal a new line... the composite sync output should trigger a total of 525 lines/NTSC, right? Then using ADC, I can check if the output value is 0 (or some value) for black, if so, add to my masking counter?
Thanks,
Danny
Post Edited (Mavromatis) : 4/12/2008 4:38:01 PM GMT
Here is the data sheet: www.intersil.com/data/fn/fn7010.pdf
Danny