Proper VGA to HDMI converter for SMPTE signals

headlesshobbs · Post by **headlesshobbs** » Sat Feb 15, 2014 9:04 am

Hey guys.

I've recently run into this issue where using an adapter to play my Dreamcast on a flat panel has lead to some problems with the contrast being all blown out of proportion. This has caused me to lose a lot of detail quality and I'm looking for an alternative solution that can handle my console's signal properly. I did make some headway with a CGA/VGA board as a passthru, but due to it's own timings I'm getting some weird pulsing effect that comes and goes which gets to be slightly annoying to deal with.

Sadly said adapter is a cheap one from Monoprice.

Edit: I forgot, "white crush" is the term I was looking for.

Fudoh · Post by **Fudoh** » Sat Feb 15, 2014 12:58 pm

Unfortunately you cannot tell before trying it. It's really hit or miss. I got half a dozen of VGA to HDMI converters - half of them gets it right while the other half has problems with the increased voltage levels of the DC's VGA signal. You can fix though by adding resistors to the RGB lines before going into the converter.

All of this has nothing to do with SMPTE timings. With every single VGA to HDMI converter you'll lose resolution on the DC's signal. The DC does output 720x480, but only the inner 640x480 area is used (except for the bootscreen and some other rare occassions). Using a VGA to HDMI converter the input signal will get sampled assuming a VESA timing. If a DC signal gets sampled like this you end up with a 640x480 HDMI signal with only 568x480 lines active.

The only way to avoid this is to use a VGA to HDMI scaler which knows can properly recognize the signal (e.g. a Gefen) or use a VGA to component transcoder and then a component to HDMI converter. This will give you a SMPTE 720x480p HDMI signal.

headlesshobbs · Post by **headlesshobbs** » Sun Feb 16, 2014 12:46 am

If it's just the RGB lines that's causing whiteout, then what type of resistors would be in a good range to use?

Now on the issue of scaling, I had better luck with the CGA board because it had a more accurate way of reading the signal without butchering it. I'm finding that some of the games you talked about were mostly made for VGA and that's pretty easy to correct when switched to 1360x768. I did some motion tests to see if there were any issues on text or other objects and they looked pretty solid. The other games that I intended to use a SLG on seem like the output is directly 640x480 and again didn't come across any issues. This is why I'm thinking I'd like to stick with using this board as an alternative to a compressed signal because I really enjoy the colour balance as it is, but as I said earlier I'd like to get rid of what causes the picture to "pulse" like the way it's doing. If I can get that out of the way, then I should be set.

Fudoh · Post by **Fudoh** » Sun Feb 16, 2014 12:55 am

don't get me wrong. The issue with VESA vs. SMTPE timings isn't a big problem. After all EVERY LCD or Plasma on the market samples the VGA input just with VESA resolution timings. I just mentioned it since you mentioned SMTPE timings.

For the resistors: it really depends on the auto-gain range of the converter. If you don't mind spending $3 instead of 30c, just get variable resistors with 50 to 200 ohms (or so).

headlesshobbs · Post by **headlesshobbs** » Sun Feb 16, 2014 3:44 pm

I was doing some more testing the other day and with my other equipment, I guess it's pretty sensitive to contrast levels that are higher then default, not just with the Dreamcast. It's more noticeable on 640x480, even from a PC in some spots.

Anyway I'm thinking about considering that other suggestion you made about doing component, but long as the tv has inputs for that I should be ok right? Also I might go ahead on doing that hack for the cable, but I'm kinda wondering if I should order the parts to make a case adapter instead?

Fudoh · Post by **Fudoh** » Sun Feb 16, 2014 4:04 pm

I would add the resistors either to the VGA/HDMI converter or to the DC VGA box (if you use one).

headlesshobbs · Post by **headlesshobbs** » Mon Feb 17, 2014 6:00 am

The converter is the source of all these problems, so I'll consider that as my primary.

Just for reference, I'll add a link to what board it is I'm working on. I haven't got much experience in soldering these things, so I'll need a little guidance on where to figure the contact points I need to work with.

http://www.monoprice.com/Product/?c_id= ... largeimage

pheria · Post by **pheria** » Mon Mar 10, 2014 5:35 am

Hey Fudoh,

Headlesshobbs referred me here from another forum regarding Dreamcast VGA output to a TV without a VGA port.

From my understanding the "white crush" effect, as well as the VESA timing mismatch, can be avoided by using a [VGA -> component] converter rather than a [VGA -> HDMI] converter?

If I were trying to decide between the [Monoprice VGA -> component] vs [Monoprice VGA -> HDMI], is the [VGA -> component] definitely the suggested route to take?

Is [VGA -> component] typically a conversion where input lag should be cause for concern? My TV is about 16-18ms which makes Space Channel 5 and other music games playable for me, but approaching 25-35ms would be a little more uncomfortable.

Fudoh · Post by **Fudoh** » Mon Mar 10, 2014 9:37 am

From my understanding the "white crush" effect, as well as the VESA timing mismatch, can be avoided by using a [VGA -> component] converter rather than a [VGA -> HDMI] converter?

The timing mismatch is avoided when using a transcoder to component, yes, but you might still run into problems with the video levels. The transcoder I use doesn't mind (Kramer FC-14), but others certainly might. It's really best to lower the voltage levels by adding variable resistors to the signal lines.

If I were trying to decide between the [Monoprice VGA -> component] vs [Monoprice VGA -> HDMI], is the [VGA -> component] definitely the suggested route to take?

no, for most people the HDMI route is better, since most TVs will have much better processing on the HDMI inputs compared to the component inputs. The timing problem probably doesn't bother most people. If you want the "best", use a VGA to component transcoder AND a component to HDMI converter.

None of these conversions adds lag.

pheria · Post by **pheria** » Mon Mar 10, 2014 4:54 pm

Thanks!

pheria · Post by **pheria** » Thu Mar 13, 2014 5:00 am

My Monoprice VGA -> HDMI converter came in and I gave it a go with some pretty bad results.

The signal flickers on and off frequently, causing it to go back and forth between black screen and Dreamcast output. At first the audio was also horrible. Everything sounded scratchy and like it was being cranked way to loud (even though the dB coming out speakers seemed quite normal. It just sounded very distorted)

I tried connecting to another TV, but had the same problem with the video. However, the audio seemed better. When I switched back to the original TV the audio was fine there as well.

For a period of 10-15 minutes it worked flawlessly, but as soon as I went back to the Dreamcast menu the video flicker started again and I wasn't able to get it to work reliably after that.

I suspect it's related to the converter box since it happened on two displays, and since connecting directly to someone else's VGA monitor didn't have this problem (ruling out the VGA cable / Dreamcast).

Quite puzzling. My first thought is to give VGA -> Component a try now, but I don't know if I should trust another Monoprice adapter if the first one (presumably) had issues with 480p / 60 Hz.

Fudoh · Post by **Fudoh** » Thu Mar 13, 2014 11:23 am

The video problems are caused by the signal levels of the DC's VGA output. The Monoprice obviously doesn't have a proper normalization circuit (which brings the video levels down before converting them). No idea about the sound issues.

headlesshobbs · Post by **headlesshobbs** » Thu Mar 13, 2014 5:54 pm

The adapter doesn't do such a great job on sound output. I went the alternative route by running it straight to the stereo.

Overkill · Post by **Overkill** » Sun Mar 16, 2014 6:48 pm

What are that crappy "VGA to HDMI" cables used for?

Fudoh · Post by **Fudoh** » Sun Mar 16, 2014 6:52 pm

they aren't. I have no idea why these exists. I wouldn't even know where the analogue RGB pins connect to on the HDMI end. I could imagine that there's projector out there, which uses somd kind of weird HDMI pinout to accept native VGA and that's a copy of the cable provided with the beamer - but for anybody else this definitely won't work.

Xyga · Post by **Xyga** » Sun Mar 16, 2014 7:20 pm

By the way Fudoh, are there any VGA to HDMI models you can recommend (available in the EU) ?

I'd like to give a try with my XRGB-2/3, Comm-Tec, Dune F, Hori UPsCv2, GBS-8220, etc...

(I plan to buy an FC-14 for my W6 anyway, but I'm curious)

pheria · Post by **pheria** » Sun Mar 16, 2014 7:24 pm

My VGA to component adapter arrived, and it's working very well. Thanks again for all of the help. I may take the advice of pairing it with a component to HDMI converter in the future, as suggested.

headlesshobbs · Post by **headlesshobbs** » Sun Mar 16, 2014 8:09 pm

Mind sharing what brand it is? Also wondering if you can do a test to see if there's anything scaling funny (i.e. text, sprites, etc)

Fudoh · Post by **Fudoh** » Sun Mar 16, 2014 8:51 pm

By the way Fudoh, are there any VGA to HDMI models you can recommend (available in the EU) ?

My best experiences so far had been with the "Manhattan" branded ones.

I'd like to give a try with my XRGB-2/3, Comm-Tec, Dune F, Hori UPsCv2, GBS-8220, etc...

The XRGBs, Dune and Comm-Tec output 720x480p though and you'd fare better with a VGA to component to HDMI chain.

pheria · Post by **pheria** » Sun Mar 16, 2014 8:53 pm

I'm using a Monoprice one. http://www.amazon.com/Monoprice-108668- ... +component

I'd be willing to help test, sure, but I don't have much experience with it nor do I necessarily have the eye for it. My library and equipment is also a little limited, but if there's a test I can do I'd be happy to follow instructions and help.

My current library is:
Crazy Taxi
Evolution
Evolution 2
Marvel vs Capcom
Marvel vs Capcom 2
San Francisco Rush 2049
Seaman
Skies of Arcadia
Sonic Adventure
Soul Calibur
Space Channel 5
Timestalkers

EDIT: I assume this isn't what you meant, but by default my TV is stretching the signal strangely. I have to explicity set the wide mode to "normal" for it to look correct to me as 4:3

Fudoh · Post by **Fudoh** » Sun Mar 16, 2014 8:58 pm

If you have Guilty Gear X you can easily check if a converter fully resolves the resolution. On a DC *any* VGA to HDMI converter will *not* properly resolve the checkerboard pattern on the bottom of the screen (the power move bars). Every half inch or so the pixels will get slightly blurry.

I'm sure there are lot of other DC games to check this as well. GGX is just my personal benchmark.

Overkill · Post by **Overkill** » Sun Mar 16, 2014 9:53 pm

they aren't. I have no idea why these exists. I wouldn't even know where the analogue RGB pins connect to on the HDMI end. I could imagine that there's projector out there, which uses somd kind of weird HDMI pinout to accept native VGA and that's a copy of the cable provided with the beamer - but for anybody else this definitely won't work.

The problem is there are cables like that being sold with an ilustration of a computer and a LCD. I know of several people buying that kind of cables expecting to work and then returning it to the sellers.

Xyga · Post by **Xyga** » Mon Mar 17, 2014 12:33 am

Fudoh wrote:
By the way Fudoh, are there any VGA to HDMI models you can recommend (available in the EU) ?
My best experiences so far had been with the "Manhattan" branded ones.
I'd like to give a try with my XRGB-2/3, Comm-Tec, Dune F, Hori UPsCv2, GBS-8220, etc...
The XRGBs, Dune and Comm-Tec output 720x480p though and you'd fare better with a VGA to component to HDMI chain.

I understand it won't be perfect but I'm still curious... or is it way too ugly to even consider it ?

Maybe I should wait for you future article about transcoders instead of trying bad stuff..

Fudoh · Post by **Fudoh** » Mon Mar 17, 2014 7:35 am

as stated before: they're fine. For example, they all perform better than the VGA port on my Sony HX9 directly. It's just important to state that there are actually hardly any real VGA sources - except for a real classic PC I would say. Everything else is 480p instead INCLUDING the Dreamcast.

XRGB-3 plus a VGA to HDMI converter performs very nicely on my W6 and I have a hard time seeing any sampling problems within the games. It's usually just the XRGB's menus that give it away.

headlesshobbs · Post by **headlesshobbs** » Mon Mar 17, 2014 8:59 am

pheria wrote:EDIT: I assume this isn't what you meant, but by default my TV is stretching the signal strangely. I have to explicity set the wide mode to "normal" for it to look correct to me as 4:3

Most panels have the habit of widening video to 16:9. Check your remote to see if you have the option to change aspect ratio and I'm sure the picture should be set up correctly.

headlesshobbs · Post by **headlesshobbs** » Fri Mar 28, 2014 12:18 am

Sorry to necro this topic, but in relation to the vga/hdmi transcoder, do you know if these things just transfer the video signal to the panel, or does it typically convert sources itself?

I spent last night fiddling around with a few hookups and I had one of those component-vga cables laying around. So far, I've been able to get anything yuv running through this thing no problem.

Fudoh · Post by **Fudoh** » Fri Mar 28, 2014 1:59 am

do you know if these things just transfer the video signal to the panel, or does it typically convert sources itself?

The A/D process involves sampling and with a SMPTE.timed source you lose resolution.

I spent last night fiddling around with a few hookups and I had one of those component-vga cables laying around. So far, I've been able to get anything yuv running through this thing no problem.

interesting. What's your source ? So you're using a 3x RCA to VGA cable into a VGA to HDMI converter (Monoprice?) and get a usable result ? If yes, I'll certainly give this a try. I mean I guess that VGA and HDMI and component to HDMI converters are basically the same, using the same IC. And maybe the IC is able to auto detect the signal.

headlesshobbs · Post by **headlesshobbs** » Fri Mar 28, 2014 3:28 am

Fudoh wrote:
do you know if these things just transfer the video signal to the panel, or does it typically convert sources itself?
The A/D process involves sampling and with a SMPTE.timed source you lose resolution.

I spent last night fiddling around with a few hookups and I had one of those component-vga cables laying around. So far, I've been able to get anything yuv running through this thing no problem.
interesting. What's your source ? So you're using a 3x RCA to VGA cable into a VGA to HDMI converter (Monoprice?) and get a usable result ? If yes, I'll certainly give this a try. I mean I guess that VGA and HDMI and component to HDMI converters are basically the same, using the same IC. And maybe the IC is able to auto detect the signal.

I'll have to take a look at text and such to see how the resolution holds up. It was something I took note of earlier (Lodoss War helped) so we'll see. Anyway I'm just using YUV from any game console via component, so it's just a surprise it even works let alone display just as good a picture as it would going the regular route. Real surprise those cables has some point of being useful afterall. I should try and find out if PS2 RGB even goes through on this thing.

PearlJammzz · Post by **PearlJammzz** » Wed Jan 14, 2015 6:23 am

Fudoh wrote:as stated before: they're fine. For example, they all perform better than the VGA port on my Sony HX9 directly. It's just important to state that there are actually hardly any real VGA sources - except for a real classic PC I would say. Everything else is 480p instead INCLUDING the Dreamcast.

XRGB-3 plus a VGA to HDMI converter performs very nicely on my W6 and I have a hard time seeing any sampling problems within the games. It's usually just the XRGB's menus that give it away.

Hope resurrecting this thread isn't too much of a bad thing but after several Google searches sent me to this same thread hopefully my clarification will help someone.

I have a DC I am also looking to hook up to a new TV. It only has HDMI and component. I also have a Framemeister. Would this same thing apply to it as the XRGB-3? DC -> VGA box -> VGAtoHDMI converter -> Framemeister -> TV. Would the Framemeister fix be signal and feed my TV what I want? Would this add tons of lag? I havent used this DC since I had a VGA-equipped TV so looking for my best options.

Fudoh · Post by **Fudoh** » Wed Jan 14, 2015 8:27 am

Would the Framemeister fix be signal and feed my TV what I want?

The VGA to HDMI converter already applies the wrong sampling rate, so resolution is already lost. The Framemeister can't fix that.

What do you want ? I would say that for 95% of all users a straight VGA to HDMI converter directly connected to the TV set is the best option. If you want better, you have to use component. You can go VGA to component to HDMI if you like though.

shmups.system11.org

Proper VGA to HDMI converter for SMPTE signals

Proper VGA to HDMI converter for SMPTE signals

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