VGA & NTSC Composite inputs converted to VGA Out - Page 1
Forum section: electronics / projects

author: UPI
author_rank: Regular Contributor
timestamp: January 01, 2013, 03:54:36 am
content: I need to build a video AB switch/converter that can take NTSC Composite video into channel A and 16 color 640x480 VGA into channel B and send one of these to an LCD as a VGA signal. The channel sent to the monitor is selected with two TTL level signals.I have modified the cheap Grandtec GVC-1000 converters to do the job in the past, but the Composite video to VGA conversion is pretty poor.http://www.tigerdirect.com/applications/SearchTools/item-details.asp?EdpNo=1208335I know there are better and more expensive off the shelf converters out there, but I would like to build my own if it can be done for under $300 or so.Got any suggestions for an IC or circuit to base this project on?

author: marshallh
author_rank: Unknown
timestamp: January 01, 2013, 07:07:43 am
content: FPGA with SDRAM frame buffer and some analog devices TV decoder, and another analog devices triple RGB DAC for VGA.

author: Psi
author_rank: Super Contributor
timestamp: January 01, 2013, 07:49:24 am
content: You might be able to use a raspberry pi + usb composite capture device + usb VGA capture device for under $300

author: UPI
author_rank: Regular Contributor
timestamp: January 01, 2013, 02:24:07 pm
content: Quote from: Psi on January 01, 2013, 07:49:24 amInteresting idea! I already have both in hand. I'll have to see what the video quality looks like.Since the Pi already has GPIO, it would be easy to do the switching control of the source.My problem is that I don't do code so I have to rely on my brother for programming. My recent description for him was that he has "the reflexes of a cat, the speed of a mongoose and the reliability of a weasel".Thanks for the suggestion.

author: UPI
author_rank: Regular Contributor
timestamp: January 01, 2013, 03:07:45 pm
content: Quote from: marshallh on January 01, 2013, 07:07:43 amDesigning this from scratch may not be financially feasible. I would probably only sell 15-20 in a 3 year period so I can't invest a lot of time/money into the development.Do you have any sample circuit diagrams available that could shorten the development time?

author: marshallh
author_rank: Unknown
timestamp: January 02, 2013, 12:04:19 am
content: If you want better quality from composite, you'll either have to do the conversion yourself or find a better converter. Then you could run it through an analog mux.http://www.digikey.com/product-detail/en/STMUX7000QTR/497-11430-1-ND/2687349

author: UPI
author_rank: Regular Contributor
timestamp: January 02, 2013, 12:15:43 am
content: Quote from: marshallh on January 02, 2013, 12:04:19 amThat is definitely a possibility. It would save me from the complexities of the converter portion.I will do some research on better off-the-shelf converters.Thanks

author: NiHaoMike
author_rank: Super Contributor
timestamp: January 02, 2013, 12:38:25 am
content: Quote from: marshallh on January 01, 2013, 07:07:43 amThat's technically the best way to do it. For even better results, use a plain ADC instead of a video decoder (so you can implement an adaptive decoder inside the FPGA) and use HDMI out instead of VGA. And if you want it to work at all, you'll really need a Tiffany Yep level of knowledge about DSPs and digital design.Quote from: Psi on January 01, 2013, 07:49:24 amI remember reading that the USB controller in the Raspberry Pi is quite limited and would probably have problems keeping up with video input and output at the same time. If you ditch the VGA output and use built in HDMI, it would probably work fine and be a surprisingly effective way to do it.On a $300 budget, you're probably best off buying a DVD recorder with component (easily converted to VGA) or HDMI output and using it only for the video conversion. You might even be able to find one for cheap where the actual DVD drive has failed but everything else still works. Or for a more direct solution, just buy a monitor that has composite input.