New feature: YPbPr/RGsB output

[Sorgelig]

All-In-One cable. Developer version

IMAG0198.jpg

[DrOG]

What does 'All-In-One' mean?
It has VGA plug on both ends, so I suppose it needs an adapter to connect it to standard SCART or component socket...
May I ask it's wiring diagram?

[Sorgelig]

I connect MiST to scaler which has VGA input, but in fact it accepts RGBHV, RGBS, RGsB, YPbPr. One switch enables HSync and VSync, another switch adds Sync to Green/Y. So, i don't need to change the cables.

[DrOG]

Wow! That's awesome! I don't have a scaler (yet), waiting the news about your own designed scaler you mentioned earlier in this topic:

viewtopic.php?f=101&t=27019&p=310749#p310705

Best regards: Gábor

[DrOG]

Hi All!

I made further investigations in the case of the MIST's different video outputs.
I used now the Amiga AGA (minimig) latest core modded by Sorgelig (YPbPr out).

Used the same methods during the test as decribed in the post below:
viewtopic.php?f=101&t=31006&start=25#p310037

As I see, the brightest and sharpest picture is over native VGA.
The second place is a 'dead heat', scandoubled component and scandoubler disabled SCART gives the same sharpness, but the YPbPr is brighter, therefore a little bit better.
The scandoubler disabled component output results the most blurred video.

That was a surprise to me, I thought the component input's quality is much superior compared to SCART connector. Perhaps the problem is in my TV set, or the advantage depends on the difficulty of adaptor: the VGA2SCART cable doesn't contain any active electronic part, unlike the VGA2YPbPr converter, which contains transistor, capacitor
and resistors too.

















I found further interesting phenomenon: in High Res Laced mode, if scandoubler is enabled, the picture is flickering, in this case the framebuffer's content is blocky. It works inversely as expected: disabling the scandoubler the picture does not flicker anymore.

[Sorgelig]

The difference in video quality is 100% related to your specific TV. Originally "sharpness" and overall quality of RGB and YPbPr video are the same. YPbPr may have a little (hardly noticeable) discoloration due to RGB-YPbPr color conversion. I don't think you will see this discoloration even on Minimig core.
Your TV has different circuits to process RGB and YPbPr. Probably there are even different chips handling different video - so result may vary from TV to TV. Greatest thing of YPbPr - it supports 31KHz natively, while SCART doesn't.

About scandoubler on Minimig - the way it implemented is absolutely wrong. Originally scandoubler is supposed to be used on progressive TV resolutions 240p/288p to make them 480p/576p. Since most retro cores provide those progressive video (with slight variations) scandoubler works perfectly. On Amiga, interlace mode is often used. And if every field will be scan doubled, we see alternating 2 different frames producing such flickering effect. So, either use non-interlace mode (like 640x256) with scandoubler, or disable scandoubler with interlaced mode - TV will provide de-interlacer and eventually will make better progressive video.

[DrOG]

Thanks for the explanation!

I was sure in the case of VGA input it's optimized for PC, that's why the video very sharp.
Using other connectors perhaps the picture smoothing is stronger, and the result is softer (not adjustable using the TV-s setup menu - perhaps next time I will look around in the service menu).

I wonder only why the 'high end' component is almost the same compared to the 'common' SCART (comparing scandoubler disabled SCART against 240p component the latter is actually weaker, but it shouldn't be).

Has anyone the same (or different) experiences on another TV? Mine is a Samsung LE40B650 LCD manufactured in 2009.

[Sorgelig]

The main purpose of YPbPr is 31KHz video where you can have either higher resolution (core developers should be advised to tweak their cores to support standard TV 480p/576p/720p resolutions) or scandoubler with HQ2x - so you will get nice picture.
Another usage of YPbPr output are TVs outside of Europe where SCART is not available.
YPbPr doesn't enhance the original picture - it only can provide higher resolutions without going out of standard (unlike SCART or VGA connections). 240p/288p/480i/576i - all these resolutions technically exactly the same for RGB and YPbPr - same sharpness, same brightness, same contrast - just different color space. If you have SCART then you can simply use original video output.

[DrOG]

I understand everything, and all of your work is very important and advantageous!

I am preferring the original methods where possible: that's why I use my TV in 4:3 AR instead of 16:9. Playing old games with my kids and friends on a 40" LCD is much more fun than on old 14" CRT (I've a Philips CM8833, but it's so small...).

Unfortunately my big TV does not support non-standard VGA signals, so using PAL cores is only possible if connected via SCART or YPbPr.

Didn't want to criticize your work, just share my experiences. Relally like the YPbPr out opportunity, it's especially practical together with the new firmware's possibility to switch between RGB<->component using the MIST's front buttons: thanks for implementing that! The 'per core settings override' is very useful as well, in connection with it one more (offtopic) question: which core's hardcoded name is PACE? (Found it on the Wiki's DocIni section, the others are clear).

Greets: Gábor

[Sorgelig]

PACE is a common core for many arcade cores. Probably one of those arcade cores didn't change the name to specific one.

[mambrino]

I've tested the YPbPr cable with my TV and interlaced modes works perfectly, but progressive ones only works for Amiga and NES cores, For Spectrum 576p works at basic/128k menu but loading games just get black screen, and for 576p C64 core always get black screen (NTSC 480p works fine). It seems that my TV has some sort of problem with 576p resolutions and certain refresh rates. Would it be possible to adjust Spectrum/C64 refresh or something to get the same behavoir as Amiga or NES core? or should I try with a scandoubler / scaler?

In any case, thanks for adjusting these cores in order to use YPbPr cable, is a very interesting solution for those (as me) who have problems with VGA modes

[Sorgelig]

It's impossible to adjust video on cores directly. It will break HW compatibility. Original ZX spectrum and C64 would have the same problem on your TV through YPbPr cable. Actually i'm not sure about C64 (it's not my core but i assume it's more or less compatible with original HW), but i'm 100% sure about ZX. Actually ZX core has 3 video timings. Probably ZX128 or ZX48 should work on your TV.

[mambrino]

None of these video timings (48,128,pentagon) works in progressive modes, i'll try with Lenkeng LKV353 scaler, hopefully it should work.

Thanks

[magecite]

So what is someone with zero soldering skills and no idea what anyone is talking about here supposed to do?

All I really want to do at the end of the day is make it so my TV can handle the Amiga cores on the Mist. Everything I have looked up is either ridiculously expensive or sounds like heaps of mucking around.

I am kinda hesitant to keep throwing money at it, as there doesn't seem to be a solution which is said to work 100%.

[Newsdee]

The MiST SCART cable should do the trick? It's not too expensive. Or you don't have SCART perhaps?

That reninds me I still haven't tried to build mine...

[bernouilli]

I just soldered a ypbpr cable yesterday. And it works great. Now I can use my mist on the TV.
However it wasn't easy to solder, as always when it comes to soldering connectors.

[Sorgelig]

Amiga core is a special case. Basically it generates "valid" video signals only when you choose standard PAL/NTSC modes.
All other resolutions from Amiga core requires very special multisync monitor sold for Amiga computer. Even scalers won't accept these resolutions.
The only way to output higher resolutions from Amiga is to implement soft scaler inside the core. Unfortunately MiST has not enough resources to implement such scaler.

[seastalker]

@magecite

This link is VERY imformative on image technology in layman's terms, and great for anyone be it USA based or not...
https://ancientelectronics.wordpress.co ... n-the-usa/

[arpalhands]

Hi,

I would like to share my realization with you.
My goal was to use standard cables and put specific stuff inside a box.
Electronic components fit on a classic PCB (2.54 mm). 4 rows and 6 columns are the minimum size I obtained with a relatively elegant circuit.
Box height is a little bit oversized but width is perfect to handle 3 RCA connectors.

Many thanks to all MiST contributors who make this possible: time to enjoy with my MiST...

Parts list:
https://www.aliexpress.com/item/New-Arr ... 23164.html
https://www.aliexpress.com/item/3PCS-LO ... 64869.html
http://www.ebay.com/itm/DB15-Female-D-S ... 2623461271
http://www.ebay.com/itm/20-x-BC547-Tran ... 0811645527
http://www.dx.com/p/jtron-1-4w-colored- ... pcs-288760
http://www.ebay.fr/itm/Condensateur-chi ... 1668162343

[DrOG]

Hi All!

Although Sorgelig's idea using an RGB->YPbPr cable was brilliant, and he made the necessary FPGA video module as well, only a few developers (actually only Gehstock) utilized his work, and limited number of cores contains it (Menu, Commodore 64, ZX Spectrum, BK0011M, SAM Coupe, Apogee, Specialist, Vector 06C, NES and Amiga/minimig).

I built recently a more or less universal RGB->component converter, as a cheap DIY solution. I would like to share it's wiring diagram, perhaps others will find it useful also (see attachment at the end of the post).

I took idea of the converter from the SEGA-16 forum below:
http://www.sega-16.com/forum/showthread ... e-BA7230LS

The picture quality is not perfect (it's a bit brighter and the picture is 'washed' compared to native RGB out, especially in cases of progressive signal), but usable. Did not test all cores so far, but as long as video output meets the PAL or NTSC TV-standard's vertical resolutions and refresh rates (240p/480i/480p@60Hz or 576i/576p@50Hz), you have a great chance that the converter will work with the given core.





Non-TV standard resolutions (800x600 - i.e. GameBoy, TRS-80, some Arcade cores; 1024x768 - Apple MacIntosh) or refresh rates (56Hz - Atari ST PAL, Videoton TVC VGA; 70Hz or more - Atari ST B&W, Amstrad's 73Hz VGA mode) will likely not work.

I tested it with my Samsung LE40B650 LCD TV, which is very sensitive and picky in aspect of non-standard video signals. In most cases it works flawless, in some cases the picture is too bright (i.e. Atari 2600 core), but connected to the Gonbes chinese scaler clone it's fine.




Tested only a few arcade and console with this scaler, they work fine, althought tried only 15kHz NTSC so far:




In other cases it works with some output mode of the core, and doesn't work with another resolutions or TV standard. I.e. the Atari ST core is OK in NTSC 240p, but 'unsupported mode' if set to 480p. The C64 core is fine using PAL standard in either 576i or 576p, but 'no signal' in case of NTSC setting.





Remarks:

* In some of my early experiments (and screenshots) appeared pale green horizontal bars on the screen, especially noticable over dark background or borders. Meanwhile I solved the problem: replaced the Huawei phone charger which feeded the circuit with another, designed for iPhone-4 (althought both have 5V 1000mA specification, the second one provides more stable voltage), and the green bands totally disappeared!







* This circuit may be a good solution for people living in NTSC countries (like U.S.) to connect their TC64 to retro displays. Here in Europe it's much better to use the minimig VGA to SCART cable - but not all cores support it, and only in interlaced (scandoubler_disabled=1) mode.

* The only exotic component of the circuit is the BA7230LS IC, I ordered it on EBay from Singapore. Althought it's designed for NTSC TV standard, works well with PAL resolutions/refresh rates as well. The color balance is acceptable also, despite the theoretically different color space. Attached some screenshots for reference, compared to the SCART and VGA image.















* In case if progressive signals (VGA out) you need to merge the separated horizontal and vertical sync using a BC547 or 548 transistor and two resistors (680ohm & 1Kohm as drawn with blue color on the schematic), as the IC accepts only composite sync ('sync on green'), and it does not have separated H/V sync input. The picture quality will be a bit weaker in this case. I built a short VGA extension cord for this purpose, which contains the necessary components in one of the connector's socket, and can be added if necessary or removed if not. If you have interlaced signal and composite sync on VGA pin 13 (this is the recommended mode if the core supports it as this results better image quality), this is unnecessary (see the dark red part of the schematics: all scandoubler_disabled=1 compatible cores have this option).




* You may connect the composite (or merged horizontal + vertical) sync signal to the IC's green input, or after the last 75ohm [R2] resistor. This does not make big difference in picture quality, and it's marked with green on the schematics.

* In some cases you need to left out the 270ohm [R1] resistor: especially if you connect a progressive signal - merged H & W sync. I used DIP switches for this purpose, but you may install a 250ohm potentiometer (they have mostly a bit bigger maximal resistance, somewhere between 260-270ohms) instead of fix resistor. In this case sometimes the value of [R2] needs to be reduced to 39ohm as well. Again I recommed DIP switches or a 100ohm potentiometer.

* I powered the circuit using a good quality (iPhone 4), standard 1000mA 5V USB phone charger.

* I could not acquire C945 transistors as the original scematic suggested, used BC182B instead.

* The IC's datasheet recommends to ground it's unused input pins (#3, #4, #5 & #20) through a 1uF capacitor, this was missing from the original circuit.

* The outer contacts of the component RCA connectors need to be grounded as well of course.

Feedback is welcome, if you have quastion about a specific core's compatibility, I'll try to answer it ASAP. I intend to test all the cores with and without the Gonbes scaler as well, but this may took a while, perhaps I'll complete it only after Christmas.

Cheers: Gábor

[DrOG]

Hi guys!

Tested the converter with non-FPGA sources, and it worked well with some modifications on the input side:

In case of Enterprise 128 it's important to use 330ohm resistors on Red, Green, Blue and CSync lines, as the computer emits (near) TTL level signals.
For details see the bottom of this page:
http://enterprise.iko.hu/pinouts.htm
But the result is fairly good:





Utilizing with standalone DVD player, you need to use a sync separator/cleaner/stripper, as these devices emit composite video over SCART pin 19 instead of pure composite sync. I.e. you need to use an LM1881, see details here: viewtopic.php?f=115&t=26963&start=111
The result was good again in case of NTSC and PAL standards as well:




So it seems to be an universal solution, and certainly usable with all kinds of R-G-B+CSync sources.

[phonedork]

All-In-One cable. Developer version
IMAG0198.jpg

Sorgelig,
Is there not a way to activate Sync on Green through software instead of a cable modification? For instance when I use my Playstation 2 in RGB Sync On Green or RGsB, I just use a normal scart cable and turn off external sync on my RGB monitor to get 480P RGsB. I can even push component through a PS2 scart by just changing RGB to component in the video settings and turn off external sync.

I am assuming the MIST works different though. But if I am not interested in component than can a software activation work for RGsB? I am interested in RGsB because I want to use both 15kz and VGA resolutions.

[Sorgelig]

1) RGsB is not tied to 15KHz only. Any resolution including VGA can use RGsB. It only depends on your monitor/TV capability. My scaler works fine with any supported resolution through RGsB.
2) It's pure HW mod. Software has no access to such control. Sync on green requires negative polarity for sync signal which is impossible to make without HW mod.
In theory, it may be possible to simulate negative polarity by shifting black to some level and use 0 as a negative value - it may reduce the effective range of video output and make white not so white but gray.
Anyway, it's up to core, as only FPGA has access to VGA output. So, core developer needs to implement such feature (if it will work).

[phonedork]

1) RGsB is not tied to 15KHz only. Any resolution including VGA can use RGsB. It only depends on your monitor/TV capability. My scaler works fine with any supported resolution through RGsB.
2) It's pure HW mod. Software has no access to such control. Sync on green requires negative polarity for sync signal which is impossible to make without HW mod.
In theory, it may be possible to simulate negative polarity by shifting black to some level and use 0 as a negative value - it may reduce the effective range of video output and make white not so white but gray.
Anyway, it's up to core, as only FPGA has access to VGA output. So, core developer needs to implement such feature (if it will work).

Yea the reason why I like RGsB is because its not tied strictly to 240p/480I like RGBs but also VGA 480P and even higher. Its versatile like component. Thats why I want to use it.

Thank you for explaining to me how it works. 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. Anyways.. Is there a way I can commission you to make me a cable?

[Sorgelig]

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.

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.