Original analog video without I/O board? Possible!

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Sorgelig
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Original analog video without I/O board? Possible!

Postby Sorgelig » Tue Aug 20, 2019 3:31 pm

Did you ever though "would be good to get original analog output without additional board which is not easy to find?
After some experiments i've made it possible!
What you need is cheap HDMI-VGA converter like this:
s-l1600.jpg

I't important the converter must be very simple! It can be like simple small adapter with hdmi and vga connectors or like on picture. The converter on picture is preferable because you can easily disassemble it to add some mods like sync-on-green or add 5V power to pin-9.
Also you can easily check the chip. Known to work well chip: AG6200. It support all kind of video from interlaced 15KHz to progressive 1080p.
Besides the video, you also get analog Audio!

Today i've released Genesis and SNES cores where this feature is implemented. You need to update the MiSTer binary as well.
In Mister.ini put the option:
direct_video=1

How it works:
Core sends original video to HDMI without any scaling, as-is. Then HDMI-VGA converter acts as a DAC for video and audio.
No any frame buffers are used in VGA converter, so it converts online.
Basically you get zero-lag video. Same as you would use VGA from I/O board.
This video is even better because you get 8bits per color while I/O board gives only 6bits per color. Audio output is also better than one used on I/O board.

It's still experimental feature, so i would like to ask everyone who has/bought such converter to test it and tell how it works.

features are supported over direct video:
- composite sync on HSync signal (set corresponding ini option).
- YPbPr (set corresponding ini option).

You will need to add sync-on-green circuit to VGA output if you need it (YPbPr requires it).
SOG can be very simplified. You just need diode (1N4148) and 1K resistor. Connection: from HSync -> anode of diode, cathode of diode -> resistor, resistor to Green signal.
Capture.PNG


SCART connection is traditional.

For SCART, YPbPr and SOG you need to use composite_sync=1
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Re: Original analog video without I/O board? Possible!

Postby Sorgelig » Tue Aug 20, 2019 3:49 pm

my collection of converters i've bought for experiment:
20190820_233936.jpg

the one in the middle doesn't work with 15KHz video. Other 3 are fine.
So, it's not bad ratio.
They are dirt cheap, so can buy several :)
Still suggest the one with "tail". Besides easy to disassemble, it has soft connection and won't harm HDMI connector as other 3.
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Re: Original analog video without I/O board? Possible!

Postby Sorgelig » Tue Aug 20, 2019 4:04 pm

Forgot to write:
Some HDMI monitors may support such video directly. At least scandoubled video.
So you basically get zero-lag original video on HDMI. No scaler involved.


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Re: Original analog video without I/O board? Possible!

Postby witchmaster » Tue Aug 20, 2019 4:17 pm

That is just superb, Sorgelig, you are a genius! :) I just ordered two adapters to try this with, one with analog audio out and one without.

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Re: Original analog video without I/O board? Possible!

Postby Sorgelig » Tue Aug 20, 2019 4:21 pm

uigiflip wrote:some have analogue audio out too

yes, i've mentioned it in my post.
So this solution is for both Video and Audio.

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Re: Original analog video without I/O board? Possible!

Postby owlnonymous » Tue Aug 20, 2019 5:12 pm

Excellent! I already have an adapter I can experiment with.

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Re: Original analog video without I/O board? Possible!

Postby robbo43 » Tue Aug 20, 2019 6:15 pm

Hi Sorgelig,

Do you have a link to the 'tail' adapter you used. All the ones I can find with a 3.5mm audio out are labelled active adpaters that also include a 5v DC input for (I quote):

Connect the USB charging cable(included in the package) to the adapter and a USB computer port or wall charger to provide additional power; USB charging boosts the signal from computers with low power HDMI ports such as the MacBook Pro with Retina Display or Raspberry Pi

I guess this is just to power the DAC chipset when there isn't enough power from the HDMI port?

The tail adapter would definitley be the best solution.

Cheers

Rob

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Re: Original analog video without I/O board? Possible!

Postby Sorgelig » Tue Aug 20, 2019 6:24 pm

many "tail" adapters include usb power as a backup power.
So, it's fine.
I've bought all adapters in local store.

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Re: Original analog video without I/O board? Possible!

Postby robbo43 » Tue Aug 20, 2019 6:58 pm

Thanks Sorgelig, I'll buy one of the active adapters and test.

Regards

Rob

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Re: Original analog video without I/O board? Possible!

Postby PsyFX » Tue Aug 20, 2019 7:37 pm

Here is a link to one that I've had for a while, its un-powered. I used with a pi3 and 4/3 lcd vga monitor. Tried a variety of resolutions, but I did not test lower then 640x480.

https://www.aliexpress.com/item/3235753 ... 4c4dsOi4kF

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Re: Original analog video without I/O board? Possible!

Postby deltax5 » Tue Aug 20, 2019 7:53 pm

That is very nice.
This will come in handy if a duel ram io comes out as i am hearing there isn't enough \pins to get the vga out for rgb, vga, component.
I really hope they just figure things out and make the 128mb ram.
We can only wait and see.
I wonder if the analogue DAC can be used also, maybe with it programed.

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Re: Original analog video without I/O board? Possible!

Postby Lightwave » Tue Aug 20, 2019 8:29 pm

I'm already using an HDMI to VGA adapter to connect MiSTer to a VGA CRT monitor.

Is there any benefit to using direct HDMI (with scan doubler) vs the regular HDMI (with scaler set to vsync_adjust=2) ?
Last edited by Lightwave on Tue Aug 20, 2019 8:40 pm, edited 1 time in total.

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Re: Original analog video without I/O board? Possible!

Postby Sorgelig » Tue Aug 20, 2019 8:33 pm

original non-scaled video

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Re: Original analog video without I/O board? Possible!

Postby loloC2C » Tue Aug 20, 2019 8:34 pm

Hello, I've just tested the direct_video mode and it was a success.

However the menu was not displaying properly since only the Genesis and SNES core were updated to support the feature. I know it's still experimental but could you update the menu core as well please ?

I could test it by directly booting into the Genesis core:

Image

Image

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Re: Original analog video without I/O board? Possible!

Postby Lightwave » Tue Aug 20, 2019 8:38 pm

Did you update the Main core as well? There is an update.

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Re: Original analog video without I/O board? Possible!

Postby loloC2C » Tue Aug 20, 2019 8:47 pm

Yes, I did.

However the menu core (the one which you boot into by default) has its own rbf file (the last one being menu_20190627.rbf) and is a core itself which for the moment does not support the direct_video mode.

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Re: Original analog video without I/O board? Possible!

Postby Sorgelig » Tue Aug 20, 2019 8:54 pm

yes, Menu core doesn't support it yet.
It will be update later

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Re: Original analog video without I/O board? Possible!

Postby SegaMan » Tue Aug 20, 2019 9:17 pm

Is 240p output possible with this HDMI to VGA Converter?

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Re: Original analog video without I/O board? Possible!

Postby Sorgelig » Tue Aug 20, 2019 9:28 pm

Menu core also updated with direct video for easier test.

SegaMan wrote:Is 240p output possible with this HDMI to VGA Converter?

Sorgelig wrote:It support all kind of video from interlaced 15KHz to progressive 1080p.

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Re: Original analog video without I/O board? Possible!

Postby glaucon1984 » Wed Aug 21, 2019 7:39 am

Sorgelig wrote:Some HDMI monitors may support such video directly. At least scandoubled video.


Does this mean we can apply force_scandoubler=1 and it will generate 30khz horizontal signal for a regular CRT VGA computer monitor?

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Re: Original analog video without I/O board? Possible!

Postby warham » Wed Aug 21, 2019 7:57 am

Does this mean you are designing a board with a fan, AG6200 chip, analogue audio connector, 128mb in the same form factor as your case to replace the other IO board :)... Merry Christmas to us?

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Re: Original analog video without I/O board? Possible!

Postby Sorgelig » Wed Aug 21, 2019 9:01 am

glaucon1984 wrote:Does this mean we can apply force_scandoubler=1 and it will generate 30khz horizontal signal for a regular CRT VGA computer monitor?

of course.

warham wrote:Does this mean you are designing a board with a fan, AG6200 chip, analogue audio connector, 128mb in the same form factor as your case to replace the other IO board

there won't be AG6200 on I/O board as there is no internal HDMI connection. So it will require some HDMI bridge board and overall it will look stupid. External HDMI-VGA is pretty fine and convenient to use.

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Re: Original analog video without I/O board? Possible!

Postby SuperSpongo » Wed Aug 21, 2019 9:21 am

This is HUGE news!! Exactly what I was looking for, thank you so much! I'll definitely test this!
I have a spare Tendak converter with a tail from my OSSC setup.

I wonder if it will output interlaced content correctly, might try Sonic 2 first :-)

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Re: Original analog video without I/O board? Possible!

Postby Lightwave » Wed Aug 21, 2019 6:19 pm

Tested using this popular Tendak dongle adapter:

https://www.amazon.com/Tendak-Converter-Adapter-Portable-Connector/dp/B01B7CEOVK/

Direct video does NOT work when connected to a Diamondtron VGA monitor (with forced scandoubler). Get no video signal at all. Adapter works fine via regular HDMI @ 640x480

Tested with MiSTer 20190820 and Menu 20190821.


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