BVM reports direct video as 480/60i

Discussion about displays and related hardware including MiSTer filters and video settings.
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Alf
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BVM reports direct video as 480/60i

Unread post by Alf »

I have an Icybox HDMI>VGA adapter and direct video enabled.

There are always two resolutions reported on each game load. If I understand correctly, the upper one is the native console output and the lower one is what the monitor actually receives.

Image

Which is already confusing to me, but OK. What really baffles me is the fact that my BVM reports 480/60i resolution, as you can see from the image. The screen however doesn't flicker, so if I had to guess, I would says it's in fact progressive.
But why does this happen and am I really getting a native 240p and is the BVM simply confused?

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Re: BVM reports direct video as 480/60i

Unread post by Gryzor »

Close, but no cookie ;)
The upper resolution is what your MiSTer is outputting through its analog VGA out, while the lower line is what you’re getting if you’re using the digital HDMI port to connect to your BVM.
You can totally keep everything set up as you have it now, if you make sure that the “Scandoubler Fx” under “Audio & Video” is activated for every core or in your MiSTer.ini file. That’s assuming your BVM can take a 31kHz input signal.
If you have the MiSTer analog board and don’t intend to mess with the scandoubler for each core, just connect a VGA to component YPbPr cable to your BVM’s input to keep everything native. I got mine from Retrogamingcables in the UK.

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Alf
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Re: BVM reports direct video as 480/60i

Unread post by Alf »

But wait, my monitor can do 240p, I don't want to double the scanlines.

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Re: BVM reports direct video as 480/60i

Unread post by Gryzor »

HDMI can’t output 240p 15kHz, only 31khz, which is why it has to use a scandoubler.
I can only recommend going with native 240p in your case, by picking up a VGA to component cable. You do have the MiSTer analog board with VGA-out, right?

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Alf
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Re: BVM reports direct video as 480/60i

Unread post by Alf »

I cannot get 15Khz with direct video? Oh damn, I didn't know that.
I guess one more reason to buy an I/O board then.

Thanks for the info!

edit
After reading this, it does seem that the monitor indeed gets tricked into thinking it's receiving a higher resolution while in fact it's drawing 240p

https://www.retrorgb.com/mister-240p-over-hdmi.html

That would explain the 480/60i thingy, right?

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Re: BVM reports direct video as 480/60i

Unread post by Atohmdiy »

This discussion is the good laugh of the day. It's always funny when a guy that don't understand crap come to disseminate his knowledge...

Anyway hdmi and direct video output 240p just fine, no reason to linedouble. Your Mister output 240p just fine as it is right now. And the BVM report 480i because it's the same signal as 240p, it's perfectly normal. All BVM report 480i when a signal is either 240p or 480i.

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Re: BVM reports direct video as 480/60i

Unread post by Gryzor »

Wow, you’re a real charmer =)
Sorry, my bad assuming HDMI also requires the scandoubler. After using that setup on my VGA monitor, I figured Alf’s BVM takes a 31 Khz signal too.

So what’s the point of an I/O board then, if one can get the same result with HDMI?

Bob from RetroRGB’s take is:
“While I prefer the features of a full MiSTer setup with an I/O board, this is a great option for people on a budget, or people who just won’t use their CRT that often.”
https://www.retrorgb.com/mister-240p-over-hdmi.html

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Re: BVM reports direct video as 480/60i

Unread post by Atohmdiy »

Your questions has been answered a thousand times. Documentation exist for a reason, both of you need to use it more often.

But i admit there could confusion about hdmi.
Minimum resolution for the hdmi spec is 31khz, so when you connect an hdmi to vga adapter to a pc, you won't be able to go below 31khz / 480p. It's not because of the adapter, it's because you graphic card can't do it.

Any hdmi to vga adapter is perfectly able to do 240p. These thing are just digital to analog converter (DAC). In direct video the mister will output 240p and the adapter will convert it to analog just fine.

And about BVM : nearly all of them are doing 240p/480i, in fact i know only the very last one (F24) that cannot. BVM are not VGA monitor by any means.

I/O board is a matter of convenience. The include DAC is not good at all (it should change), same for a lot of hdmi to vga adapter in direct video.

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Alf
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Re: BVM reports direct video as 480/60i

Unread post by Alf »

Atohmdiy wrote: Wed Jun 05, 2024 11:57 am

BVM are not VGA monitor by any means.

Well, Martin's clone cards do offer a VGA input and since A and D series of BVMs are multiformat, you could argue that this combination creates a kind of an VGA monitor. Limited of course to 60Hz refresh rate.
As for the I/O board, the DAC on the official one really is bad so I have high hopes for the upcoming Misteraddon's variation. Also, don't forget the audio output which is missing on the DE10.

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Re: BVM reports direct video as 480/60i

Unread post by Atohmdiy »

Alf wrote: Wed Jun 05, 2024 12:10 pm
Atohmdiy wrote: Wed Jun 05, 2024 11:57 am

BVM are not VGA monitor by any means.

Well, Martin's clone cards do offer a VGA input and since A and D series of BVMs are multiformat, you could argue that this combination creates a kind of an VGA monitor. Limited of course to 60Hz refresh rate.
As for the I/O board, the DAC on the official one really is bad so I have high hopes for the upcoming Misteraddon's variation. Also, don't forget the audio output which is missing on the DE10.

No they are not close to a vga monitor at all. BVM are built for standardized video format that were used in the video industry. Traditionally their input is RGBs with BNC. This is not VGA, VGA is RGBHV. Martin decide later in the design to add another BNC to authorize both RGBs and RGBHV. This allow greater flexibility but it's not the pro and broadcast monitor's standard.

Also PC VGA monitors are multisync in their support frequency, which bvm are not at all, and they don't support 15 khz either. So no their is nothing similar :D

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Alf
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Re: BVM reports direct video as 480/60i

Unread post by Alf »

Well the type of sync makes no difference in the end, you get the same image regardless of how you handled sync.
But of course you are right, PVMs/BVMs are not VGA monitors :)

Also, while I have you here, maybe you can help with a weird problem on my A14.
When connected to my PC (RTX 4070) via an HDMI>VGA adapter, I get no problems at 480p. But when going 720p, the strangest thing happens. When I move the mouse cursor to the right side of the screen, I get interference like this;

Image

The interference follows the cursor and disappears when the cursor goes back to the left side of the screen :shock:

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Re: BVM reports direct video as 480/60i

Unread post by Atohmdiy »

I can be wrong but it looks like you are using the wrong modeline.
With wrong modeline the image could be stable but garbage come when there is movement.
There is modeline here :
https://www.mythtv.org/wiki/Modeline_Database

Try these :
1280 720 60 Hz 44.9576 kHz ModeLine "1280x720" 74.18 1280 1390 1430 1650 720 725 730 750 +HSync +VSync
1280 720 60 Hz 45 kHz ModeLine "1280x720" 74.25 1280 1390 1430 1650 720 725 730 750 +HSync +VSync
1280 720 59.94 ModeLine "ATSC-720-59.94p" 74.176 1280 1320 1376 1650 720 722 728 750
1280 720 60 Hz ModeLine "ATSC-720-60p" 74.25 1280 1320 1376 1650 720 722 728 750

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Re: BVM reports direct video as 480/60i

Unread post by LamerDeluxe »

One advantage of using an Analog IO board is that you can have an HDMI display and an analog display hooked up at the same time.

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Re: BVM reports direct video as 480/60i

Unread post by Optiroc »

“240p” is just a hack based on standard 480i timings. BVMs display it just fine but the OSD doesn’t say “240p” since it’s not a broadcast term. I don’t know if it was a term at all in the 90s… In my circles we just called it “non-interlaced”.

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