Posted By
Lacus
on 2016-03-05
12:01:48
|  Composite video to VGA converter
Hello Guys! I would like to ask your help reagarding this video to VGA converter.
Is there anybody who use it to connect the Plus/4 to VGA monitor? Unfortunately, I am not able to "make" good picture. My best result is:
I tested the composite input (RCA) and S-video input of converter, but the result is the same. I saw some videos about it on Youtube with C64. According to these videos it should work. I assume that the video output of C64 is same as Plus/4's. Am I right?
Thanks for your help in advance!
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Posted By
Chicken
on 2016-03-05
13:20:42
 | Re: Composite video to VGA converter
What's the native resolution of your LCD monitor? Does it have an aspect ratio of 4:3 or 5:4? It's hard to tell from your photos. If it's not 4:3, that might be an issue.
Yes, the video signal is the same. (Not going into details and all the possibilities to mess with the signal on plus/4  )
Though, there are some differences between plus/4 and C64 "screen content". Different dot clock causes larger pixels (in x-dimension) on plus/4. So sometimes with a C64 hooked up to a display you have quite a bit of visible border area on the sides and with a plus/4 you can barely see it.
Another issue: The S-VHS output on plus/4 suffers badly from crosstalk. TLC pointed this out to me some years ago. I've never noticed this back then on my 1802 monitor. When I checked this on a bigger TV with composite input I was surprised that the luma signal alone is pretty colorful 
So in many cases the composite signal offers better picture quality, even if the S-VHS signal should provide the better quality theoretically.
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Posted By
Lacus
on 2016-03-05
14:06:51
| Re: Composite video to VGA converter
The aspect ratio is 5:4.
The maximum resolution is 1280x1024 @ 75 Hz.
FACTORY PRESET TIMING TABLE:
MODE RESOLUTION HORIZONTAL FREQUENCY (KHz) VERTICAL FREQUENCY (Hz)
1 640×350 @70Hz 31.469 70.087
2 640×400 @56Hz 24.827 56.424
3 640×400 @70Hz 31.469 70.090
4 640×480 @60Hz 31.469 59.940
5 640×480 @67Hz 35.000 66.667
6 640×480 @72Hz 37.861 72.809
7 640×480 @75Hz 37.500 75.000
8 720×400 @70Hz 31.469 70.087
9 800×600 @56Hz 35.156 56.250
10 800×600 @60Hz 37.879 60.317
11 800×600 @72Hz 48.077 72.188
12 800×600 @75Hz 46.875 75.000
13 832×624 @74.6Hz 49.725 74.500
14 1024×768 @60Hz 48.363 60.004
15 1024×768 @66Hz 53.964 66.132
16 1024×768 @70Hz 56.476 70.069
17 1024×768 @75Hz 60.023 75.029
18 1024×768 @75Hz 60.150 74.720
19 1152×864 @75Hz 67.500 75.000
20 1152×870 @75Hz 68.681 75.062
21 1152×900 @66Hz 61.846 66.004
22 1280×720 @60Hz 45.000 60.000
23 1280×768 @60Hz 47.776 59.870
24 1280×960 @60Hz 60.000 60.000
25 1280×1024 @60Hz 63.981 60.020
26 1280×1024 @75Hz 79.976 75.025
In addition, the picture vibrates a little bit independently of any settings (resolution, frequency)
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Posted By
Chicken
on 2016-03-06
08:26:24
| Re: Composite video to VGA converter
Do you know the converter's output resolution? Can you change it? If it can't be set to your display's native resolution (1280x1024), rescaling will cause artefacts.
Not sure what's causing the vibrating picture. Might be the plus/4's not 100%-PAL-signal. Old TVs and monitors usually were less strict about this and displayed what they were fed. With new (all digital) TVs and monitors it's a different story. Even your converter might not like the plus/4's signal.
Nevertheless, still think that the display's aspect ratio (5:4) causes some issues. Do you know someone with a 4:3 display? You should check out the converter hooked up to a 4:3 display.
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Posted By
Lacus
on 2016-03-06
11:11:06
| Re: Composite video to VGA converter
I can change the resolution of converter and I tested all of possibilities. (800*600/1024*768/1280*1024/1440*900/1600*1200/1600*900/1366*768/1680*1050/1920*1080/1920*1200)
Unfortunately a quality is the same (like a wrong black and white TV).
However, when I connect the video output of Plus/4 to my old CRT TV's RCA input, the quality is OK.
I think also that the converter does not like the signal of Plus/4 or the converter is wrong.
My TV also has VGA input and I will test it. I am curious.
UPDATE!
I tested it on my flat TV and the result is a little bit better, but very far from normal AV. The colours are pale and the vibration is still existing.
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