New feature: YPbPr/RGsB output

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Re: New feature: YPbPr/RGsB output

Postby phonedork » Wed Feb 28, 2018 8:12 pm

Sorgelig wrote:
phonedork wrote:I have a original XBOX that runs sync on green and I see reddish tent in the grays. I remember hearing about how it may have something to do with the negative polarity. I wonder if there is a cable mod that can be done to fix that as well.

There may be several things caused this. May be XBOX RGsB has reduced range on G due to sync and your TV doesn't understand it. May be G has shifted level while RB aren't again due to sync. Or may be something wrong in timings so TV cannot adjust the levels correctly. I don't know if there is any fix for that.

phonedork wrote:Is there a way I can commission you to make me a cable?

I don't sell the cables, sorry. It's supposed to be done by yourself.
Or may be someone else here is willing to do this for you.


Thank you Sir!

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Re: New feature: YPbPr/RGsB output

Postby MasterOfGizmo » Sun Sep 09, 2018 10:45 am

I just made myself one of those cables. Works like a charm with my samsung tv. I immediately added support to the atari st and c16 cores.

But are you sure the capacitor is the correct direction? The Y output will be pulled low by the TVs 75 ohms termination resistor. So the output terminal will be lower than the input from vga.

Secondly what's the exact purpose of the transistor? It seems like it's meant to mix hsync and vsync. But vsync is static 3.3V and hsync already carries a composite sync.
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Re: New feature: YPbPr/RGsB output

Postby DrOG » Sun Sep 09, 2018 1:07 pm

MasterOfGizmo wrote:...
Secondly what's the exact purpose of the transistor? It seems like it's meant to mix hsync and vsync. But vsync is static 3.3V and hsync already carries a composite sync.

It mixes the CSync and the Green or Y (luminance).

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Re: New feature: YPbPr/RGsB output

Postby MasterOfGizmo » Sun Sep 09, 2018 3:13 pm

The transistors base is constantly pulled high and thus imho never switches. The y and cs mixing is imho be done by the 680 ohms resistor and the cap.
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Re: New feature: YPbPr/RGsB output

Postby Sorgelig » Sun Sep 09, 2018 6:24 pm

MasterOfGizmo wrote:I just made myself one of those cables. Works like a charm with my samsung tv. I immediately added support to the atari st and c16 cores.

But are you sure the capacitor is the correct direction? The Y output will be pulled low by the TVs 75 ohms termination resistor. So the output terminal will be lower than the input from vga.

Secondly what's the exact purpose of the transistor? It seems like it's meant to mix hsync and vsync. But vsync is static 3.3V and hsync already carries a composite sync.

Cannot tell about capacitor. Transistor is required as it mixes Sync to Y/G in both modes 15KHz and 31KHz. As you know, YPbPr supports both 15KHz and 31KHz sync, so this circuit universal and works in both cases CSync and HVSync.

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Re: New feature: YPbPr/RGsB output

Postby DanyPPC » Sun Sep 09, 2018 6:45 pm

Thanks for all information. I think the Sorgelig cable adaptor is more simple to be realized.

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Re: New feature: YPbPr/RGsB output

Postby DrOG » Sun Sep 09, 2018 6:52 pm

I don't think that the polarity of the capacitor is critical, as I have built my cable 2 years ago following the original schematic and it still works flawless.

Another option is to build a sync merger using a logical IC, i.e. a 74LS86 or a 4070, they can be feed from one of the USB ports of the MiST. Examples in this topic:
viewtopic.php?f=115&t=31322

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Re: New feature: YPbPr/RGsB output

Postby Sorgelig » Sun Sep 09, 2018 7:13 pm

Transistor circuit doesn't require power supply and it works on current signal levels, so it's the best circuit.

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Re: New feature: YPbPr/RGsB output

Postby DrOG » Mon Sep 10, 2018 3:07 am

I agree, but if you have positive H, V or C Syncs on VGA pins 13 and/or 14, the IC circuit is superior in aspect of compatibility, as is always produces a (standard) negative C-Sync at the end. If you want you may replace th LS IC with a HC (or HCT) variant.

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Re: New feature: YPbPr/RGsB output

Postby Sorgelig » Mon Sep 10, 2018 6:06 am

If don't take RGsB output, then YPbPr output requires the core update anyway, so correct sync polarity should be set inside the core. Why you need external logic if you lave plenty of them inside FPGA? ;)

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Re: New feature: YPbPr/RGsB output

Postby DrOG » Mon Sep 10, 2018 8:53 am

You're right, but I'm not familiar with FPGA programming, and there are some abandoned cores, like Apple ][ or ColecoVision, which have non-standard (reversed) sync polarity...

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Re: New feature: YPbPr/RGsB output

Postby slingshot » Mon Sep 10, 2018 10:45 am

DrOG wrote:You're right, but I'm not familiar with FPGA programming, and there are some abandoned cores, like Apple ][ or ColecoVision, which have non-standard (reversed) sync polarity...

I also wasn't familiar until last summer, so it's a bad excuse :)

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Re: New feature: YPbPr/RGsB output

Postby MasterOfGizmo » Mon Sep 10, 2018 12:54 pm

Sorgelig wrote:Transistor is required as it mixes Sync to Y/G in both modes 15KHz and 31KHz. As you know, YPbPr supports both 15KHz and 31KHz sync, so this circuit universal and works in both cases CSync and HVSync.


Ok, that makes sense. Although all cores i've seen to far have extra logic to generate CompSync in YPbPr mode even with the scandoubler enabled. So the transistor could probably be omitted. But it really doesn't hurt ...
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Re: New feature: YPbPr/RGsB output

Postby Gehstock » Mon Sep 10, 2018 1:50 pm

DrOG wrote:You're right, but I'm not familiar with FPGA programming, and there are some abandoned cores, like Apple ][ or ColecoVision, which have non-standard (reversed) sync polarity...



Better? Controls taken from MiSTer Port



Is a wild mix of different Implementations
Last edited by Gehstock on Mon Sep 10, 2018 8:22 pm, edited 1 time in total.

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Re: New feature: YPbPr/RGsB output

Postby MasterOfGizmo » Mon Sep 10, 2018 6:28 pm

Sorgelig wrote:Cannot tell about capacitor. Transistor is required as it mixes Sync to Y/G in both modes 15KHz and 31KHz. As you know, YPbPr supports both 15KHz and 31KHz sync, so this circuit universal and works in both cases CSync and HVSync.


Having thought about this a little more I am pretty sure the transistor would not be able to properly mix HVSync as that requires some XOR type of logic (which the cores all have). Otherwise there would be no hsync during vsync in the resulting composite sync.

Just out of curiosity I removed the transistor and the 1k resistor and just directly connected the 680 ohms resistor to VGA pin 13 and still everything works. Am still not convinced about the cap polarity. On one hand there is the 75 ohms pull down in the receiver. But the Sync is imho meant to add a DC offset. I am really not good at these analogue things ...
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Re: New feature: YPbPr/RGsB output

Postby DanyPPC » Mon Sep 10, 2018 6:44 pm

Gehstock wrote:
Better? Controls taken from MiSTer Port
ColecoVision_MiST.rar


Is a wild mix of different Implementations


This core have incorrect colors, at least on VGA MiST output.

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Re: New feature: YPbPr/RGsB output

Postby Gehstock » Mon Sep 10, 2018 7:00 pm

all other works?

Edit : Sound should repaired
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Re: New feature: YPbPr/RGsB output

Postby Sorgelig » Mon Sep 10, 2018 7:35 pm

MasterOfGizmo wrote:Having thought about this a little more I am pretty sure the transistor would not be able to properly mix HVSync as that requires some XOR type of logic (which the cores all have). Otherwise there would be no hsync during vsync in the resulting composite sync.

Just out of curiosity I removed the transistor and the 1k resistor and just directly connected the 680 ohms resistor to VGA pin 13 and still everything works. Am still not convinced about the cap polarity. On one hand there is the 75 ohms pull down in the receiver. But the Sync is imho meant to add a DC offset. I am really not good at these analogue things ...


Even some cores provide CSync as (hsync | vsync) or (hsync & vsync). This is not fully complaint with TV standard, yes. But it works, especially if VSync is short, so TV's free run HSync oscillator still in-sync.
The original circuit has been created to exiting hardware with minimum required components. If MiST would have Component video originally, then it could include more complex and more proper mixing circuit.

If all cores will be recompiled to output CSync in both 15KHz and 31KHz modes in RGsB and YPbPr, then transistor is not required. But using resistor is not a good idea as it will pulls up and pulls down, while transistor only pulls up. May be diode should be added sequentially to resistor.

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Re: New feature: YPbPr/RGsB output

Postby DanyPPC » Mon Sep 10, 2018 7:37 pm

Nothing to do. This ColecoVision has incorrect colors and distorted sound.

All other cores (YPbPr changes) work on my MiST.

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Re: New feature: YPbPr/RGsB output

Postby DrOG » Tue Sep 11, 2018 4:36 am

Gehstock wrote:all other works?

Hi!

I tried it with my BenQ BL912, and both RGB and YUV works, although the colours have a bit different shades, see screenshots (same as on NES core).

Thanks for your work adding new feature to this otherwise abandoned core! :cheers:

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Re: New feature: YPbPr/RGsB output

Postby MasterOfGizmo » Tue Sep 11, 2018 6:10 am

The conversion from RGB to YPbPr is a color space conversion. And the screen converts back to RGB or whatever it uses internally. So I wouldn't be surprised if the colors in both modes differ. I'd even expect this effect to vary from screen to screen.
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Re: New feature: YPbPr/RGsB output

Postby MasterOfGizmo » Tue Sep 11, 2018 6:21 am

Sorgelig wrote:But using resistor is not a good idea as it will pulls up and pulls down


Why would that hurt?
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Re: New feature: YPbPr/RGsB output

Postby Gehstock » Tue Sep 11, 2018 7:48 am

Is the Sync ok now?

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Re: New feature: YPbPr/RGsB output

Postby MasterOfGizmo » Tue Sep 11, 2018 8:09 am

DrOG wrote:You're right, but I'm not familiar with FPGA programming, and there are some abandoned cores, like Apple ][ or ColecoVision, which have non-standard (reversed) sync polarity...


I just adjusted the sync polarity of the apple ][ core. Find it at:
https://github.com/mist-devel/mist-bina ... appleii%2B

But i am too stupid to use it. How does one load/run a nib image? Or has this been broken by firmware updates?

Once it's working it should be rather easy to add YPbPr support. Adding 15kHz support is a little more work as the scandoubler includes vital parts of the video circuitry and cannot just be omitted.
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Re: New feature: YPbPr/RGsB output

Postby DrOG » Tue Sep 11, 2018 2:43 pm

Gehstock wrote:Is the Sync ok now?

Sorry, my bad :oops:

I remembered wrong, not the ColecoVision core was problematic, but some other:

-Videopac(Odyssey 2) +/+
-Chip8 (SuperChip) +/-
-Mattel Aquarius -/+

Although both sync signals should be - at 640x480@60Hz.

ColecoVision was not problematic, but now it is, although my BenQ tolerates it well.

Sorry again, my mistake, and I deserve the punishment :shrug:


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