Dreamcast official VGA box

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thebigcheese
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Re: Dreamcast official VGA box

Post by thebigcheese »

There's also a brightness control on the Toro, don't know if that actually helps with anything though.
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Kez
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Re: Dreamcast official VGA box

Post by Kez »

thebigcheese wrote:There's also a brightness control on the Toro, don't know if that actually helps with anything though.
I think that's more like a bug labelled as a feature. Just seems to add a grey overlay to the whole image.
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andykara2003
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Re: Dreamcast official VGA box

Post by andykara2003 »

クリスチャン wrote:Looks like the Dreamcast DAC is not that great. Boosted levels, slightly noisy video, and slightly uneven colors.
Interesting - it’s funny because the Dreamcast's VGA output has always been viewed as impeccable by the retro community in the past.
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Fudoh
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Re: Dreamcast official VGA box

Post by Fudoh »

na, maybe in terms of sharpness (and that's a valid statement even today), but the fact that the video levels are overblown has been known for ages.
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andykara2003
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Re: Dreamcast official VGA box

Post by andykara2003 »

Ahh OK, I hadn't picked up on that, good to know.
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Lawfer
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Re: Dreamcast official VGA box

Post by Lawfer »

maxtherabbit wrote:I would wait until the RGC cable is actually released before dismissing it
If you use 480i instead of 480p, do you still have issues with overblown video levels and RGB levels or those issues only affect 480p?
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maxtherabbit
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Re: Dreamcast official VGA box

Post by maxtherabbit »

Lawfer wrote:
maxtherabbit wrote:I would wait until the RGC cable is actually released before dismissing it
If you use 480i instead of 480p, do you still have issues with overblown video levels and RGB levels or those issues only affect 480p?
I have not tested 480i specifically, but the issues are the same on 240p - so I would say yes they affect all modes
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クリスチャン
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Re: Dreamcast official VGA box

Post by クリスチャン »

andykara2003 wrote:Ahh OK, I hadn't picked up on that, good to know.
Honestly the vast majority of this information is not widely known. It's not like how most people in the retro scene know about 1 chip SNES vs 2 chip. This is especially true regarding the whole aspect ratio and sampling thing. That issue wasn't "widely" exposed until the OSSC came about, and even Digital Foundry missed some info about what exactly is different with the DC's VGA output. They just mentioned sample rate; which is only half of the story.

For whatever reason the DC just doesn't get enough coverage on these things.
headlesshobbs
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Re: Dreamcast official VGA box

Post by headlesshobbs »

Can someone test a cga/vga converter on the DC just to help me confirm something?
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maxtherabbit
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Re: Dreamcast official VGA box

Post by maxtherabbit »

headlesshobbs wrote:Can someone test a cga/vga converter on the DC just to help me confirm something?
The gbs8200? Yeah I just got mine
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Re: Dreamcast official VGA box

Post by headlesshobbs »

So now that I got some of my equipment in order, I decided to so a little test to find out what devices the DC has a problem with.

Test game - SoulCalibur/Sophitia Stage

Monoprice VGA to HDMI Converter - Fail
(No Name) HD Video Converter - Pass
CGA/VGA Converter - Pass
Open Source Scan Converter - Adjust to 6-7 Pass

Direct connection to PC CRT - Pass
Direct connection to LCD/LED (past test) - Fail


The one's that fail is where the issue on accepting the analog conversion is being done improperly. I know the levels are high for it's output, but in the past I've never seen this problem until digital came along and even with PC systems at the normal settings, I've experienced the wrong level of contrast saturation being applied. This is a note on all who are in the business of making analog/digital converters to monitor their calibration settings as the problem lies with them and not just a single gaming console alone. (This test is 10+ years old btw)
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orange808
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Re: Dreamcast official VGA box

Post by orange808 »

If you absolutely must buy a standalone ADC, hunt down some higher quality gear. Chinese stuff sucks.

Extron DVC RGB-HD A does a good job. It also recognizes and samples the Dreamcast aspect ratio properly.

In addition to ADC, it brings low pass filtering and EDID management with a PC.
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Endymion
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Re: Dreamcast official VGA box

Post by Endymion »

maxtherabbit wrote:the official VGA box buffers H/V sync through a 74HCT244 and contains coupling caps for RGB

the toro does not contain any scaling logic, so I'm not sure where they are getting "pixel scaling issues" from - that really makes no sense
I just assumed they were referring to the fuckery that a modern display does to a Dreamcast's wider-than-normal VGA signal. No?
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maxtherabbit
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Re: Dreamcast official VGA box

Post by maxtherabbit »

Endymion wrote:
maxtherabbit wrote:the official VGA box buffers H/V sync through a 74HCT244 and contains coupling caps for RGB

the toro does not contain any scaling logic, so I'm not sure where they are getting "pixel scaling issues" from - that really makes no sense
I just assumed they were referring to the fuckery that a modern display does to a Dreamcast's wider-than-normal VGA signal. No?
probably, but why try to put that on the box? ANY RGB or VGA output solution is going to do the same thing
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Re: Dreamcast official VGA box

Post by Endymion »

It didn't seem to me they were putting it on the box, it's just the case that if you use the thing with an HDTV you'll have that kind of weirdness yeah? I don't know that the Toro was really marketed to anything but die-hard CRT gamers, but there's always going to be someone wanting to plug something like that up to their brand new OLED or whatever. And it's a natural point to make if you are comparing it with the DCHDMI particularly.
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maxtherabbit
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Re: Dreamcast official VGA box

Post by maxtherabbit »

Endymion wrote:It didn't seem to me they were putting it on the box, it's just the case that if you use the thing with an HDTV you'll have that kind of weirdness yeah? I don't know that the Toro was really marketed to anything but die-hard CRT gamers, but there's always going to be someone wanting to plug something like that up to their brand new OLED or whatever. And it's a natural point to make if you are comparing it with the DCHDMI particularly.
obviously it was misleading, since a couple people in this very thread were believing that the official VGA box from sega behaved differently in that regard
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darcagn
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Re: Dreamcast official VGA box

Post by darcagn »

Endymion wrote:I don't know that the Toro was really marketed to anything but die-hard CRT gamers
The ability of the Toro to output 31KHz RGBS over the SCART connector means it's the only all-in-one solution to hook up the DC to a Framemeister. I know this was an intentional marketing decision on their part because Beharbros sent me a free Toro so I could test it with my Framemeister.
nmalinoski
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Re: Dreamcast official VGA box

Post by nmalinoski »

darcagn wrote:The ability of the Toro to output 31KHz RGBS over the SCART connector means it's the only all-in-one solution to hook up the DC to a Framemeister. I know this was an intentional marketing decision on their part because Beharbros sent me a free Toro so I could test it with my Framemeister.
Not quite. The Toro is the only solution that is always readily-available for purchase. thefoo.83 on eBay has made Dreamcast SCART cables with a mode switch that will produce 480p, just like the Toro, but without the fuss or obnoxious depth added to the footprint of the console.
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Kez
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Re: Dreamcast official VGA box

Post by Kez »

nmalinoski wrote:obnoxious depth added to the footprint of the console.
Have to agree with this, I pretty much gave up on the Toro because it was such a pain to keep it all wired up without something coming disconnected or falling down the back of my shelves, or the connector cable breaking. It's an unnecessarily large box on the end of a fairly rigid, yet incredibly fragile cable, and connectors coming out of the sides at annoying angles.
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darcagn
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Re: Dreamcast official VGA box

Post by darcagn »

nmalinoski wrote:
darcagn wrote:The ability of the Toro to output 31KHz RGBS over the SCART connector means it's the only all-in-one solution to hook up the DC to a Framemeister. I know this was an intentional marketing decision on their part because Beharbros sent me a free Toro so I could test it with my Framemeister.
Not quite. The Toro is the only solution that is always readily-available for purchase. thefoo.83 on eBay has made Dreamcast SCART cables with a mode switch that will produce 480p, just like the Toro, but without the fuss or obnoxious depth added to the footprint of the console.

Well yeah, anyone can make their own custom cables. Before the Toro or thefoo.83 were doing it I made one and published the schematic. He might even be using my schematic as a reference, who knows.
thebigcheese
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Re: Dreamcast official VGA box

Post by thebigcheese »

And RGC has one coming out soon.
thchardcore
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Re: Dreamcast official VGA box

Post by thchardcore »

Konsolkongen wrote:
Gunstar wrote: Interesting that the official SEGA box blows out some details going by those comparison shots.

Edit: DF article with comparison
It does, but adding a very small resistor to each of the RGB lines will solve this completely. I think I settled on about 10 ohms on mine.

My experience with other brands of VGA boxes (one of the old transparant ones) does indeed confirm what Digital Foundry says. Years ago I ran my Dreamcast through a Gefen DVI Scaler exclusively and I was only able to get pixel perfect scaling using the original box from Sega.
Thank you for the tip regarding the output being too high. I was able to desolder the leg of each of the 220uf capacitors in the official VGA box and put a 20ohm resistor tied to each capacitor legs (capacitors turned on their sides). Output is perfect now and not all blown out.
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thchardcore
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Re: Dreamcast official VGA box

Post by thchardcore »

Follow up post - seems the resistor mod disturbed the impedance of the output and now I have ghosting...
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Konsolkongen
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Re: Dreamcast official VGA box

Post by Konsolkongen »

thchardcore wrote:Follow up post - seems the resistor mod disturbed the impedance of the output and now I have ghosting...
Is it possible to take a picture of this? I haven’t noticed anything like that on mine, but I can take a look if I have something to compare against.
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bobrocks95
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Re: Dreamcast official VGA box

Post by bobrocks95 »

Will hop onto this to comment again that good VGA solutions remain scarce for the Dreamcast. Most recently made cables are SCART focused which is a shame for a console that natively generates HV sync.

Has anybody tried the DC2VGA board from Jeff Chen? https://github.com/jeffqchen/DC2VGA

Just caps, resistors, and some XOR gates so it's going to require the same OSSC pre-ADC tweaks I figure. But onboard CSync seems relatively compatible and I'd be interested to try the Dreamcast plugged into the OSSC's AV1 to see if LPF helps with my image problems.
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Gunstar
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Re: Dreamcast official VGA box

Post by Gunstar »

There's a similar device from Chipnetics too, the 'DreamBaby'
Image
Purists will note that Dreamcast does output Csync on the AV Multi-out on pin 10; however this specific CSync signal is generated from an encoder (and not via the GPU) resulting in a significantly degraded image, compared to that from a sync combiner. Also this specific Csync signal is disabled in 31Khz mode!
No mention of the hot RGB levels though, so I assume it's similar to Jeff's board
thchardcore
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Re: Dreamcast official VGA box

Post by thchardcore »

Konsolkongen wrote:
thchardcore wrote:Follow up post - seems the resistor mod disturbed the impedance of the output and now I have ghosting...
Is it possible to take a picture of this? I haven’t noticed anything like that on mine, but I can take a look if I have something to compare against.
Sure. Noticeable on the text of the GDEMU screen.
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bobrocks95
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Re: Dreamcast official VGA box

Post by bobrocks95 »

Gunstar wrote:There's a similar device from Chipnetics too, the 'DreamBaby'
Purists will note that Dreamcast does output Csync on the AV Multi-out on pin 10; however this specific CSync signal is generated from an encoder (and not via the GPU) resulting in a significantly degraded image, compared to that from a sync combiner. Also this specific Csync signal is disabled in 31Khz mode!
No mention of the hot RGB levels though, so I assume it's similar to Jeff's board
Nice to see another option. It sounds like the CSync is generated in the same way ("Premium sync-combiner transistor" = an XOR gate, right?). I don't like the exposed PCB or the jumper for 15/31kHz though, a switch is preferable for the games you can trick into 480p by swapping between them.
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thchardcore
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Re: Dreamcast official VGA box

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Konsolkongen
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Re: Dreamcast official VGA box

Post by Konsolkongen »

I don’t have a GD Emu in my Dreamcast. Is it visible in the BIOS?
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