RGB > CVideo,S-Video and VGA, self made!

[vibros]

Hello,

here is my last product: a card that convert the RGB signals from an Amiga RGB port to CVideo/S-Video/VGA, to make easy to connect a lot of video device.
This is not the first card of this type, but it offer something different



Follow the pictures of CVideo from this card (plugged in a plain A1200), compared to the on board CVideo of the same computer

HiRes



LowRes



SuperHiRes



The kickstart picture from an A600, with my card (on the left) and with the on board CVideo out (on the right).



The picture that come from this card has a bigger flaw of colors, but it is not so visible: it is like a little flicker on the bord of some lines, then this lines are much thin.
The picture that come from the on board CVideo of an A600/A1200 has less flaw of colors but it is much more blurred (in SuperHiRes, the image is unreadable).

VGA



S-Video



From a plain A500 (VGA is not usable on a OCS Amiga)

CVideo



The card plugged in an A500



Regards
Stefano

 

[Zetr0]

@Stefano

That looks great my friend!

The VGA output is that at 15.7KHz or is it double to 31.4Khz ?

 

[vibros]

Hello,

@Zetr0, i am only an hobbyist!

This card dont modify the video signals of the Amiga, but help the user to solve some problem about the type of monitor to use with it! If the workbench is capable of a monitor (in devs/monitor) with 30/31khz of horizontal frequency, then if you attach a vga cable between this card and your monitor, you will see the workbench on it. Very simple!
You can attach at the same time VGA, CVideo and S-Video on the same monitor, to select a monitor VGA compatible on the workbench, and enjoy to play with your Amiga with different screens (VGA and not) on the same television.

Regards
Stefano

---------- Post added at 15:37 ---------- Previous post was at 15:32 ----------

Hello,

i wish to add more infos. The hard task to project this card was the filter section on the chroma line. I have spent many months to obtain a good solution. The other parts are simple: a video encoder and a buffer needed for some signals...that's all!

Regards
Stefano

 

[maw2k]

has it a built in "sync strainer"?

 

[vibros]

has it a built in "sync strainer"?

Hello,

i dont know what is a "sync strainer". This card dont modify the sync signal, but only give a Composite-Video and a S-Video signal with the same sync in input. That mean if the video signal in input is about 15KHz, in output it is the same. To use the VGA output, the input sync signal need to be 31KHz.
There is another question: this device is PAL. Can be NTSC, but need to be tested with some parts with different values.

Regards
Stefano

 

[AmmoJammo]

I assume this is just a CXA1145/CXA1645 or similar? basically what's already contained in the A600's and A1200's to begin with

What does the other IC on the RGB output do though? I'd guess maybe an opamp?

I dont really see the point of this to be honest... I mean, the "VGA" output is just the normal RGB amiga signal, passed through a few more ICs, with no additional processing...

You can easily modify the A600 and A1200 for an SVideo output without an external circuit, as the CXA1145 already has the chrome and luma outputs, just needs a simple drive circuit.

 

[vibros]

I assume this is just a CXA1145/CXA1645 or similar? basically what's already contained in the A600's and A1200's to begin with

What does the other IC on the RGB output do though? I'd guess maybe an opamp?

I dont really see the point of this to be honest... I mean, the "VGA" output is just the normal RGB amiga signal, passed through a few more ICs, with no additional processing...

You can easily modify the A600 and A1200 for an SVideo output without an external circuit, as the CXA1145 already has the chrome and luma outputs, just needs a simple drive circuit.

Hello,

what you have write is right! But:

the Composite Video output give a more sharped and readable picture respect the output on the A600/A1200

this device work in all Amiga models

I have here three pcs of this card, one live on my A1200.

Regards
Stefano

 

[maw2k]

has it a built in "sync strainer"?

Hello,

i dont know what is a "sync strainer".

https://www.amibay.com/showthread.php?p=365762 its was about a RGB2VGA adapter.

Do you plan on using the machine with a Video Toaster? Just be aware that there are two versions of the Commodore adapter, and the -01 version doesn't work correctly when the Toaster activates genlock mode. The -03 version fixes this as it has a built in "sync strainer" that automatically generates H+V sync from the composite sync line when genlock mode is active.

 

[AmmoJammo]

Hello,

what you have write is right! But:

the Composite Video output give a more sharped and readable picture respect the output on the A600/A1200

this device work in all Amiga models

I have here three pcs of this card, one live on my A1200.

Regards
Stefano

It is odd that the inbuilt composite doesn't give a good image, and from my own testing I know its no better than RF!

I wonder if the Amigas have some extra filtering, or lack thereof, on the composite output that makes it so inferior... or just poorly chosen components..

 

[vibros]

has it a built in "sync strainer"?

Hello,

i dont know what is a "sync strainer".

https://www.amibay.com/showthread.php?p=365762 its was about a RGB2VGA adapter.

Do you plan on using the machine with a Video Toaster? Just be aware that there are two versions of the Commodore adapter, and the -01 version doesn't work correctly when the Toaster activates genlock mode. The -03 version fixes this as it has a built in "sync strainer" that automatically generates H+V sync from the composite sync line when genlock mode is active.

Hello,

OK, i have learned something more! I see if i can add this option in a future version of my card.

Regards
Stefano

 

[Bryce]

I think what AmmoJammo is trying to say, is that the A600 and A1200 contain a CXA1145 which can also give a very sharp S-Video signal, you just need to add the S-Video socket and make three connections. This is how I connect my machines too.
I would also be interested in learning more details about your PCB and what ICs you've used. I think your card is more interesting for A500 users, that really don't have any decent outputs other than the standard composite and RGB.
I also produce a very similar PCB with just S-Video output, but it is based on the AD724, which you obviously aren't using (it's only available as SMD).

Bryce.

 

[Bryce]

Sorry for the double post, but I was looking at your PCB pictures again and I can't see any line impedance resistors on the circuit board?? How are you achieving the 75Ohms without these?

Bryce.

 

[status]

Hello, nice skills mate, are you planning on getting it commercial or open hardware?

If the later, can we have, please, the schematics ? xD

 

[vibros]

Hello status,

your question is right, but i am not a profi and this device is very simple: it is a little bit more then a Sony test board (the ic is a Sony CXA). I have put it on sale here

https://www.amibay.com/showthread.php?t=49019

why to made this device i have spent much time and a few money to purchase the components, that are new. That mean that the schematic of this device has not much value.

Regards
Stefano

---------- Post added at 15:09 ---------- Previous post was at 15:06 ----------

Sorry for the double post, but I was looking at your PCB pictures again and I can't see any line impedance resistors on the circuit board?? How are you achieving the 75Ohms without these?

Bryce.

Hello Bryce,

what you search is on the bottom side of this device.

Regards
Stefano

 

[Bryce]

Ah, tricky. I didn't realise you'd put SMD components underneath. Nice solution.

Bryce.

 

[vibros]

Hello,

i have some unsolved questions about this device and a reply from experts is more then welcome.
I have tested the SVideo output of this device on one of my television (a big Samsung LCD TV, of the year 2005/2006), with an SVideo2SCART adapter (that is very easy, without electronic devices inside). This TV has two SCART input and, on the first SCART connector, the SVideo output of my device is properly recognized: the picture is bright, colorful and sharp, without flaws of colors, very beautyful, like an SVideo source is.
On the second SCART connector, the SVideo output of my device is not properly recognized: the picture is bright, but with flaws of colors and sometimes, there is a loss of colors (only the luminance signal is displayed).
I think that on this second SCART connector, the video signal is interpreted to be a composite signal and showed with a loss of quality.

I have read that this is normal with televisions with two SCART input.

I have another LCD TV, cheaper, with only one SCART input connector. On this television, the SVideo output of my device (through a SVideo2SCART adapter) give the same picture of poor quality, like on the second SCART connector of the big Samsung TV.

Someone has tested this device with a Benq projector, that come with a SVideo input connector, and then, compared the picture with the quality of a CD32 (that has SVideo output built in): the consolle of Commodore show a better picture, and my device is not properly recognized. It show a picture like a composite source.

I think that this projector, through the SVideo input, manage the picture like a composite picture (add luminance to the chrominance like a CVideo input), then the result is a picture with less flaws of colors on CD32, but more blurried, like the CVideo output of this Amiga.
This is my theory, and not confirmed. If someone of you know this matter, your reply is welcome.

Regards
Stefano

 

[Bryce]

Hi Vibros,
can you possibly make a screenshot of the output signal on an oscilloscope, with some sort of voltage reference?
Also can you tell me what IC you are using to convert the signal or even better, could you send me the schematic and I will check it against a reference design (I will not pass it on to others or whatever if you want it kept secret).

Bryce.

 

[scap61]

i'm from Piacenza Italia and i'm interested about your device

 

[vibros]

Hello,

a little update with review.

The outputs are three, always active: is responsability of the user do not damage the video device.
The output are CVideo, S-Video and VGA. This adapter is not a scandoubler, so the VGA output is active even if the signal is about 15 KHz on the horizontal sync.

Now some pictures from a CRT monitor (with a SCART2CVideo/S-Video adapter):

the CVideo on the Early Menu screen



on a HiRes Workbench



on DPaint



The image has flaws. There is a regulator on this adapter, to gain the best quality on CVideo. VGA output is not affected and it has ever the best quality.
Anyway, as already wrote, CVideo image is sharpe and clear, much better then the original CVideo output from an A600/A1200. To paint with a paint program is very easy and funny: you have just an easy cable with an RCA connector. The quality is ok!
On a Workbench screen, the characters of a text, where contiguous pixels alternate dark and white colors, give more flaws, and the quality of the image is less clear.

The S-Video on the same CRT monitor with the same adapter from a SCART connector: the monitor do not understand the S-Video input, just the luminance, and the picture is gray!



Now CVideo on a LCD monitor (on this monitor a resolution of 640x512 is very stable,without flicker)



and S-Video, more clear and sharp, very good indeed!



As said, VGA output is the best, with no reduction of quality. Refer to the pictures on the previous posts!

Thanks for watching!

 

[Tymo3210]

Do You still have it?
I am interested in. Where is photo of device?