Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Everything Else Anything related to audio / video / electronics etc) BUT remember- we have many new forums where your thread may now fit! .... Parts, Equipment & Tools, Construction Tips, Software Tools......

Help me get a handle on this RGB thing
Help me get a handle on this RGB thing
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Thread Tools Search this Thread
Old 26th February 2012, 01:12 AM   #1
AudioFox is offline AudioFox  United States
diyAudio Member
AudioFox's Avatar
Join Date: Jun 2006
Default Help me get a handle on this RGB thing

I've been playing with some video circuits lately and I have to admit it's given me a headache. It's not that I can't find any information, it's just that I can't find any reliable information. It seems like when it comes to video, everyone's an expert but they all disagree

Anyway, here's what I wanted to know - I have a lot of old stuff, like laserdisc players, VTRs, video games and computers, etc... with SCART connectors or BNC jacks that output a System M analog RGB signal + composite sync or RGB + sync-on-green. Thing is, I've also got several new TVs that only have VGA inputs... I know how to separate sync from green and separate horizontal + vertical sync, so we'd have all of the same signals as VGA, but what about the other stuff like frequencies and voltage?

Here's what I know about NTSC-M:
525 lines (~480 for video)
30 frames per second
2 fields per frame
60 fields per second
Horizontal sync frequency: 15.734 kHz
Vertical Sync: 60Hz
Video = 0.7V pk-pk
White level = 1V
Black level = 0.3V
Sync level = 0V

Here's what I know about VGA:
525 lines (~480 for video)
60 fields per second
Horizontal Sync Frequency: 31.4684kHz <Exactly double the NTSC rate
Vertical Sync: 60Hz
Video = 0.7V pk-pk
Black level = 0.3V
Sync level = ? <Sources say negative, but is that really negative or just more negative than the video signal
Frame rate = ? <Is it 60 progressive frames or 30 interlaced frames?

So how do we get an NTSC-M picture to display on a VGA TV? Will it work if I just use an IC like the NJM2257 sync separator to split horizontal and vertical sync, or would I have to do something more like double the h-sync frequency or de-interlace it?

Sorry in advance if someone's already asked this, I just got so sick of searching for this and finding nothing but VGA-to-TV convertors and people who don't know the difference between frames and fields or RGB and those stupid "component" jacks they put on everything nowadays
  Reply With Quote
Old 26th February 2012, 09:30 AM   #2
dangus is offline dangus  Canada
diyAudio Member
Join Date: May 2004
Location: Vancouver Island
When it comes to scan rates, there is no easy conversion. You have to capture the entire frame then spew it out at twice the rate. Boxes that did this for the benefit of folks with giant VGA monitors or data grade CRT projectors were called "line doublers" or "video scalers", and expensive. (Although these days you can find DVDO iScan doublers on eBay for around $50, with VGA output. They were the budget scaler in their day, a bargain at under $1000.) A minority of VGA monitors were compatible with standard definition scan rates, like the NEC Multisync II. TVM made a multisync knock-off which had an accessory, oddly called the "TV Mouse", which converted composite video to RGB. (This could be done with one chip (TDA3330?), as published in Radio-Electronics magazine, but the chip has long been obsolete.

About the cheapest way to convert from standard definition to VGA is to buy a tuner box from eBay or Dealextreme (or possibly the bargain table at a local computer dealer). Search ebay for LCD VGA TV tuner; about $30. Or (even cheaper) use a video (TV) capture card in a PC and run Dscaler.

The more practical but expensive solution is to "invest" in a nice A/V receiver, usually a 7.1 model, which has a built-in scaler that upconverts regular video to HDMI.
  Reply With Quote
Old 27th February 2012, 02:04 PM   #3
SoNic_real_one is offline SoNic_real_one  United States
diyAudio Member
Join Date: Jan 2008
Location: Virginia
1. VGA sync is "negative" in respect to signal polarity. That would be 0V if the black is at 0.3V. There is an option for "positive" sync - that would be at 1V.
2. VGA is 60p as opposed to NTSC 60i. You need a NTSC source that can convert to 480p (DVD players ca do that easy, not so much for LD).

What was said above is correct.
  Reply With Quote


Help me get a handle on this RGB thingHide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
how would you handle this a/b switching? thegnu Instruments and Amps 4 16th January 2009 02:10 AM
How to handle very old caps Bassterror Power Supplies 2 15th August 2006 11:17 AM
Can we handle more zen? bertjan Pass Labs 10 31st July 2006 11:04 AM
Too hot to handle Panelhead Pass Labs 3 8th May 2003 01:10 AM

New To Site? Need Help?

All times are GMT. The time now is 04:09 PM.

Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.79%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright ©1999-2017 diyAudio