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 Post subject: GreenAntz RGB-to-YPbPR component converter
PostPosted: Mon Apr 05, 2021 11:37 pm 


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Joined: 24 Jul 2016
Posts: 335
I was lucky enough to score a GreenAntz RGB-to-YPbPr/component converter that Zebidee the creator sent to me for testing purposes, and I have to say I’m pretty impressed. The PCB is nice, with a few different connector options and the like. It’s not as expensive as a lot of easy alternatives, but even so it feels like it's built to give a result, not just built to a price. It’s all hand-assembled, though I think bespoke is probably a better term.

The unit I received has a VGA (DB15HD) input jack, which did limit my testing a little bit. I’d have liked to try a few old consoles like the SNES, for some classic SMW comparison shots, but I have no way currently to get a SCART signal into the GreenAntz. Instead, I decided to go for most of my testing with Supermodel, that being the flavour of the month with gm-matthew’s recent full-speed network builds. Testing was done at 480i, though I'm aware others are getting similar results with 240p. The GreenAntz is powered by a USB C plug, which was super convenient for use with a PC.

I can only say I’m impressed. I was testing the output of a crt_emudriver-enabled laptop on an Ikegami TM10-17RA 10” 450TVL shadow-mask 15kHz broadcast monitor, and with the contrast and chroma set right I would genuinely struggle to tell the difference between RGB and YPbPr. To the point that if someone else had set everything up I’m not sure I would have been able to pick which was which. The little Ikegami is a fantastically sharp and vibrant unit, and there was no loss of colour or sharpness at all. There was perhaps the tiniest of colour balance differences – which is more than made up for by the fact you can dial the chroma up for extra saturation if you want to. That’s the main reason I like having a converter even though all of my setups take RGB.

I was a little confused by the colour balance pot on the unit, as it didn't seem to do much. On speaking to Zeb though, he explained how colour-accurate the circuit is, and that the difference the pot makes it hard to spot with the naked eye, and more something to be measured with a scope or sensor. He also mentioned that the pot might be left off future models as it's not really needed. I'm also aware of how much work he's been putting into the sync conversion, so i imagine if you're having trouble with sync then the GreenAntz might be work a look.

There's now a switch to have the unit take C-sync or separate H- and V-sync, which makes this an option for MiSTer as well (say, if you want to skip the IO board and get better video from an HDMI-to-VGA dongle. You'd get the GreenAntz for about the same money as the IO board, though you'd need to think about a VGA to SCART cable, mb, to use it for consoles as well. Still a cheaper option overall.)

I know how much work Zebidee has been putting into the GreenAntz, and it really shows. There are a number of great RGB-to-YPbPr converters out there, and this is certainly one of them.

If you want to buy one Zebidee is taking orders, i think. He's a member on here, and is also on AussieArcade, ArcadeControls and the CRT Collective :)

NOTE: I tried to take some photos but the results weren’t very good – nothing to do with the converter; I can’t use a camera. I have no idea how to do anything other than point and click. But in person the results the GreenAntz provided were so close to indistinguishable from the original RGB signal that I’d be kidding myself if I said one image was better than the other.


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 Post subject: Re: GreenAntz RGB-to-YPbPR component converter
PostPosted: Tue Apr 06, 2021 12:14 am 


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Joined: 05 Mar 2018
Posts: 1558
buttersoft wrote:
though you'd need to think about a VGA to SCART cable, mb, to use it for consoles as well.

I make console dongles that convert from the multi out to DE-15 (VGA) which would pair nicely with this device to do away with SCART all together


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 Post subject: Re: GreenAntz RGB-to-YPbPR component converter
PostPosted: Tue Apr 06, 2021 1:57 am 


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Joined: 24 Jul 2016
Posts: 335
maxtherabbit wrote:
buttersoft wrote:
though you'd need to think about a VGA to SCART cable, mb, to use it for consoles as well.

I make console dongles that convert from the multi out to DE-15 (VGA) which would pair nicely with this device to do away with SCART all together


Yes it's definitely a case of picking your ecosystem :) The GreenAntz is going to work happily around a few options.


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 Post subject: Re: GreenAntz RGB-to-YPbPR component converter
PostPosted: Tue Apr 06, 2021 4:28 am 


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Joined: 05 Nov 2019
Posts: 752
Location: Massachusetts, USA
The Linuxbot3000 doesn’t need a switch for RGBS or RGBHV, definitely something worth being integrated into this transcoder in future releases imho. Always glad to see more options out there!
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For CRTs, A/V gear, video games & more, be sure to check out my eBay!

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 Post subject: Re: GreenAntz RGB-to-YPbPR component converter
PostPosted: Tue Apr 06, 2021 1:53 pm 



Joined: 05 Nov 2020
Posts: 12
Location: THAILAND
Thanks for the review buttersoft, I appreciate it.

There is now an RGB SCART input version of GreenAntz available, which is perfect for use with consoles.

You can now select H+V or composite sync modes with a simple switch.

kitty666cats wrote:
The Linuxbot3000 doesn’t need a switch for RGBS or RGBHV, definitely something worth being integrated into this transcoder in future releases imho. Always glad to see more options out there!


I am sorry but I must respectfully (and reluctantly) correct this kitty - I have two of linuxbot's transcoders and have just been testing them. Neither of them works properly with composite sync input, they only produce proper sync when fed separate H+V inputs. Maybe you have had a different experience?

I also note that linuxbot's transcoder actually DOES have a jumper to choose between H+V or composite sync modes, but it doesn't seem to do anything useful (like allow it to actually work with composite sync input):

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The other thing to note is that I used two PCs with different video cards (win7+HD6450 and WinXP+X1050), both setup with CRT_emudriver, to test linuxbot's transcoder. It couldn't produce sync from the XP machine at all but managed OK with the Win7 machine.

There is absolutely nothing "wrong" with the XP machine, it works fine with every other 15khz display I have via RGB or component. It always works with GreenAntz. The only thing not working is the composite sync on the linuxbot transcoder. I tried both of my linuxbot transcoders and same results.

Measuring signals with a scope, the differences between the two machine's video outputs were minimal. The XP machine was around 40mv higher in Hsync, and about 40mV lower on Vsync output levels. Nothing out of the ordinary, but this seems to have been enough to confuse the sync logic on linuxbot's boxes.

Here is a picture of linuxbot's vertical sync period when using with my XP machine in H+V mode. You might notice that there are no sync pulses generated all. Just a big flat line.

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I couldn't get a picture on my component-modded TV with linuxbot's, but I was able to get a pic on my Sony despite no sync being present at all. That jagged bit at top is where the TV isn't quite sure what to do with no sync, until it figures out where to start again:

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Here is a pic of the linuxbot sync when it is actually working with Win7 machine in H+V input mode. Notice the spiky bits around the waveform tops and edges?

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Here are a couple of pics of GreenAntz sync (looks identical for both H+V and composite input), which I think looks much cleaner. IMO picture on TV looks cleaner too. Note the half-length horizontal period around the vertical sync period, which mean "interlaced mode". If these peaks, edges and tops are not clean and well defined, some TVs can lose sync.

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I really like Jam and his transcoder, I just wish it was a bit more reliable for my purposes.

For composite sync input testing I used one of buttersoft's 15khz protection dongles that also convert H+V into composite sync (these are very handy). All scope shots are done using a simple Owon USB scope, but it does the job.


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 Post subject: Re: GreenAntz RGB-to-YPbPR component converter
PostPosted: Tue Apr 06, 2021 2:25 pm 


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Joined: 16 Jan 2014
Posts: 1384
Buttersoft, can you post pics of the unit itself and links for description / purchase?

I find the best eye test for comparing RGB to component (RGB converted to component) to be the title screen for Super Mario World, specifically the RGB letters on the screen. While very close, almost every comparison Ive seen shows a bit of difference on the Reds. Its hard to describe it, but pure RGB signal colors always seems a bit "smoother" or more pleasing to me. Its so close though, it may be down to different brightness levels between the signals.


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 Post subject: Re: GreenAntz RGB-to-YPbPR component converter
PostPosted: Tue Apr 06, 2021 5:58 pm 



Joined: 05 Nov 2020
Posts: 12
Location: THAILAND
Josh128 wrote:
Buttersoft, can you post pics of the unit itself and links for description / purchase?

I find the best eye test for comparing RGB to component (RGB converted to component) to be the title screen for Super Mario World, specifically the RGB letters on the screen. While very close, almost every comparison Ive seen shows a bit of difference on the Reds. Its hard to describe it, but pure RGB signal colors always seems a bit "smoother" or more pleasing to me. Its so close though, it may be down to different brightness levels between the signals.


GreenAntz comes with a "colour balance" pot which actually attenuates Pr output, so that you can match Pb and then luma (with the other pot) for the optimal "balance".

Even though my colour perception mostly reliable, I don't rely on eye-based tests for a bunch of reasons I won't go into right now. I follow the data and the math. When I do, my eyes just confirm O.o

Soooo, I collected a lot of data and did projections and error analysis on what we collected, compared empirical data for different scenarios with predicted mathematical ideals. Even made charts :D Anyway, I could (did) literally circle a calculated "superset" range of values for optimal balance between Pb, Pr and luma to maximise accuracy by minimising transcoding error (there is always some error in analogue transcoding).

GreenAntz comes with pots pre-calibrated. The colour balance and luma pots could be replaced with fixed resistors to hit theoretical optimal balance between all three "components" of the video signal. But people have different colour perception and I have better appreciation for that than most. So we've left the pots on for now as it gives people some choice. Still worry it makes things too complicated, so views always welcome.

If interested to buy please PM me here or on BYOAC or wherever else you find me :D

Earlier posts:

http://forum.arcadecontrols.com/index.p ... 245.0.html
http://forum.arcadecontrols.com/index.p ... 249.0.html

Some pics of the latest GreenAntz including sync selector:

Image

Image


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