Dreamcast VGA + my HDTV

[broken harbour]

Ok, I know, this subject has been done to death but I actually have a few options and I don't know what I should use.

First off, I have a 60" LG 60PS60 Plasma, it's a great TV, and I don't notice any lag on it. But it doesn't have a VGA input, neither does my receiver.

I was thinking of just buying a Hanzo VGA box, and then buying a VGA + Audio to HDMI converter, and running that to my HDMI switch but http://junkerhq.net/xrgb/index.php/Dreamcast doesn't recommend this, but doesn't really go into detail why.

However, if you follow that link, it says that a Gefen VGA to HDMI converter produces a superior image... but that's a $320 box! Also, will running a 240p signal via HDMI even be possible for the games that support 240p?

I also have a Framemeister, but from what I can tell I'd have to buy a sync combiner and run it into my scart switcher, which currently maxed, and I'm lazy and don't like cable swapping...

So.... what do I do? Is there another option I'm not thinking of?

[bobrocks95]

HDMI spec specifies a 25MHz minimum pixel clock, which is too high for 240p 60Hz video.

[CkRtech]

I was thinking of just buying a Hanzo VGA box, and then buying a VGA + Audio to HDMI converter,

I would wait for the TORO from the same guy who made the Hanzo. It should be out any day now. It can do 15/31 output over either VGA or SCART (selectable) and should work perfectly (provided it is built well) with the Framemeister.

[beharius]

Just few days left, either Saturday or Sunday...

[Unseen]

HDMI spec specifies a 25MHz minimum pixel clock, which is too high for 240p 60Hz video.

Which is why the CEA timing for 240p (and 480i) specifies that every pixel should be sent twice for a transmitted resolution of 1440x240p. There is even an optional 2880x240p mode specified with the rationale that you can use various (integer) pixel repetition factors to get effective horizontal resolutions close to or matching older video game system. I'm not sure if there is any HDMI source that uses that mode though.

[broken harbour]

I was thinking of just buying a Hanzo VGA box, and then buying a VGA + Audio to HDMI converter,

I would wait for the TORO from the same guy who made the Hanzo. It should be out any day now. It can do 15/31 output over either VGA or SCART (selectable) and should work perfectly (provided it is built well) with the Framemeister.

lnik me?

[Fudoh]

http://shmups.system11.org/viewtopic.php?f=6&t=51568

[bobrocks95]

HDMI spec specifies a 25MHz minimum pixel clock, which is too high for 240p 60Hz video.

Which is why the CEA timing for 240p (and 480i) specifies that every pixel should be sent twice for a transmitted resolution of 1440x240p. There is even an optional 2880x240p mode specified with the rationale that you can use various (integer) pixel repetition factors to get effective horizontal resolutions close to or matching older video game system. I'm not sure if there is any HDMI source that uses that mode though.

You have outdone me Unseen Sensei. So it's a standard they specified that likely has never been used before?

[Unseen]

So it's a standard they specified that likely has never been used before?

Wouldn't be the first one ;)

The pixel-doubled 480i is quite common, for example in Bluray players that offer "always use original resolution" output modes. As for 240p in either the 1440 or 2880 variants... I would actually be surprised if there is no test signal generator out there that supports at least one of these, but I have no clue if there is anything that supports it "for real". I suspect most devices that have source content in 240p can just upscale it internally. Two candidates that spring to mind are PS1 games on the PS3 (IIRC output as 480p?) and older Wii Virtual Console titles on the Wii U (no idea what happens there).

[Fudoh]

The pixel-doubled 480i is quite common

care to elaborate ? 15khz through HDMI is nothing special. And no trickery involved either.

240p through HDMI - by the way - works on the Framemeister.

[Unseen]

The pixel-doubled 480i is quite common

care to elaborate ? 15khz through HDMI is nothing special. And no trickery involved either.

Yes, that's what I said. As mentioned by bobrocks95 HDMI requires a minimum pixel clock of 25MHz, but standard 15kHz modes are way below that with a pixel clock of just 13.5MHz. To transmit them correctly via HDMI the standard requires that each pixel is sent twice, which increases the pixel clock to 27MHz and thus puts it into the legal range for HDMI. If you don't believe it, copies of CEA-861 as well as various versions of the HDMI specifications are available "unofficially" on the net.

I suspect this difference between the transmission of 240p/480i and higher-resolution modes over HDMI may be one of the reasons why some Component/VGA-to-HDMI converters only work with 480p or higher resolution input signals.

240p through HDMI - by the way - works on the Framemeister.

I know - it accepts almost any odd resolution via HDMI even when the signal is pure DVI without info frames, although once it decided that the incoming signal is using pixel-doubling it's hard to convince it that the source has gone back to a non-pixel-doubled signal. The start screen of FFCC on the Gamecube doesn't look that nice anymore when it is reduced to 360x480 by omitting every second pixel.

By the way, what was your 240p source?

[Fudoh]

If you don't believe it

I believe the specs, but I don't believe that it's universally used like this.

By the way, what was your 240p source?

It's been some time. Probably some component 240p source run through an A/D converter.

[Unseen]

If you don't believe it

I believe the specs, but I don't believe that it's universally used like this.

If pixel doubling is not used for 15kHz modes, compatibility seems to suffer a bit. I just ran a small test with an FPGA board configured as 720x240p signal source without pixel doubling - the DVI/HDMI clock signal was confirmed to be 13.5MHz by scope measurement.

Devices that accepted the signal with no issues:

• Samsung T27C270
• Sharp LC22LE320E
• Reflexion LED1014DV (crappy 10" portable TV with HDMI in)

Devices that had problems:

• Dell U2410: Immediately entered power save mode
• XRGB Mini: detected input as 360x240p, threw out every second pixel
• DVDO Edge: blue screen, "Unsupported Signal" in input info

[broken harbour]

Ok so my Toro box came in. So if I read this correctly, I can just hook it up via scart to my scart switch and get 480p over scart to my framemeister? Or do I still need to covert VGA to scart to get 480p?

[HydrogLox]

Or do I still need to covert VGA to scart to get 480p?

No, you should be good to go. The 21-pin RGB connector always has RGBS - the RGB switch (7) controls whether 15kHz RGB (240p/480i) or 31kHz RGB (480p) is generated by the Dreamcast and the 21 pin RGB connector carries the selected signal. You only need to fiddle with the hidden push button (10) if you want CSync on the DE-15 (VGA) connector.

Toro DC VGA Box Manual

If it was me I'd try it first without the SCART switcher - that way if it is fine at first and then looks funky when you get the switcher involved you know who to blame (no reason to expect it to go wrong but ...).
I'm also not sure whether a sync cleaner/stripper integrated into a third party XRGB-Mini SCART RGB to Mini-DIN-8 adapter could have an (adverse) effect on the signal.