Shmups Forum
* FAQ    * Search
 * Register  * Login 
It is currently Mon Jan 25, 2021 10:03 am View unanswered posts
View active topics

Post new topic Reply to topic  [ 3 posts ] 
Author Message
 Post subject: Laptop to CRT TV troubleshooting
PostPosted: Tue Dec 15, 2020 10:20 am 

Joined: 15 Dec 2020
Posts: 1
Hello everyone, I registered to this forum just to ask for your help.
I am a complete noob, but I tried my best to follow the setup guide from Calamity on how to connect my PC to a CRT TV with CRT Emudriver.
But unfortunately I have ran into some issue. Instead of writing a long post, I decided to record a video to show my problem.
I apologize for the poor video quality.

 Offline Profile  
 Post subject: Re: Laptop to CRT TV troubleshooting
PostPosted: Mon Jan 11, 2021 11:29 pm 

User avatar

Joined: 21 Jun 2019
Posts: 73
Location: Atlanta, GA
Three weeks and no response so I wanted to contribute. Not the best person to answer not having tried getting a computer video signal to work on a television but I've done the reverse.

You're right to prefer analog VGA to analog Composite over digital HDMI to analog Composite. The yellow cable is Composite video, white is left+right audio for mono sound so is correct to use over the red. The "RCA" refers to the plug type versus the video format since Component and RGB can also use RCA-style plugs.

Would help to find an online manual for the Panasonic television and verify if it accepts both 50 Hz and 60 Hz video. Search the model number printed somewhere on the back. Japan is NTSC so I'd expect only 60 Hz.

Background Information (slightly simplifying things)
VGA is nice that the "color space" is encoded the same between PAL and NTSC but the framerate (vertical sync) needs to match what the television supports: 50 PAL or 60 Hz NTSC. I know PVMs and some televisions sold in PAL regions can support both. 59.94 Hz is also acceptable for NTSC for dumb historical reasons of being backwards compatible with black & white television. Video resolution can be from 240p to 1080p and at 15 kHz, (very rare) 24 kHz or 31 kHz horizontal sync. The BIG divide is computers running at 31 kHz and consumer televisions at 15 kHz (and PAL and NTSC use slightly different 31/15 kHz values). This is why you need CRT Emudriver. VGA is also nice for being RGB and separating the R, G and B colors on their own wires.

Composite video is much lower quality than VGA's RGB but have to use what you got. Only defined to exist at 480i and 576i resolution at 15 kHz hsync and 50/59.94/60 Hz vsync. CRT Emudriver is reducing the laptop's hsync from 31 to 15 kHz to solve one problem but the screen resolution is another problem. 240p you may hear about is something of a hack of 480i and also supported by VGA and Composite. Annoyingly, the "color space" is encoded on different subcarrier frequencies between PAL and NTSC. This is important later. Composite is not nice for combining all color and brightness information on the same wire, which causes interference and makes the video blurry.

About the screen resolution: 480i/576i exists on CRTs at an ideal 640x480 (480i) NTSC or 768x576 (576i) PAL resolution at 4:3 ratio after horizontal scaling. If CRT Emudriver lets you output a 4:3 resolution close to that then doesn't hurt to try.

Possible Solution A
Black and white video from a color Composite (or S-Video) signal is caused by a PAL television or monitor getting NTSC video or NTSC television or monitor getting PAL. While it can account for the wrong vysnc (50 or 59.95/60 Hz), it looks in the wrong place for color information, sees none, so assumes signal is black and white. So I immediately assume your VGA -> Composite cable is encoding to the wrong format. In fact, it's a bad sign that the cable doesn't take an external power source. No way a passive converter would be any good. Could be taking 5V signal from VGA but still would prefer to see external USB power source.

So yes, I agree with you talking about getting another converter. Make sure it's VGA -> Composite, not Composite -> VGA. Cables converting video types usually aren't bidirectional. VGA doesn't carry sound so I'm confused why the cable has white and red audio wires. Just run audio cable from computer to television. 3.5mm to RCA audio adapters are very cheap and do not need external power.

Possible Solution B
The vertical scrolling and jittering suggest the hysnc and vysnc frequencies are slightly off-spec. Here's where I'd want to be familiar with CRT Emudriver. You showed a 49.500 Hz vsync. You definitely want that at 50.000 Hz for PAL. 60.000 or 59.940 Hz for NTSC. The Hsync component has some out of spec tolerance, especially on (analog) CRTs, but ideally, you want 15.625 kHz for PAL and 15.734 for NTSC. I don't think 15.620 is an issue but change to 15.625 if possible. If video is still black and white then see Solution A.

Possible Solution C
Here in North America, people mod CRTs to get RGB and yet in Europe, you have people throwing RGB SCART televisions away. If you can get an RGB SCART television, you can easily convert the CRT Emudriver 15 kHz VGA to RGB SCART and get a very high quality signal. Just be sure on cable direction. Failing all else, you can go the HDMI route. You shouldn't need CRT Emudriver for HDMI either.

All Solutions
See about CRT Emudriver outputting a 4:3 resolution close to 640x480 NTSC or 768x576 PAL. Or an integer multiple of that.

 Offline Profile  
 Post subject: Re: Laptop to CRT TV troubleshooting
PostPosted: Wed Jan 13, 2021 12:41 pm 

User avatar

Joined: 05 Nov 2019
Posts: 609
Location: Massachusetts, USA ... o-adapter/

All these will work for 240p, I suggest the first two
For CRTs, A/V gear, video games & more, be sure to check out my eBay!


 Offline Profile  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 3 posts ] 

All times are UTC

Who is online

Users browsing this forum: marqs and 17 guests

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum

Search for:
Jump to:  
Space Pilot 3K template by Jakob Persson
Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group