OSSC (DIY video digitizer & scandoubler)

[marqs]

I just checked GBI on my setup (official component cable) and didn't bump into sync detection problems. Line2x and Line2x 240x360 displayed without issues, passthru and Line3x 240x360 were beoynd capabilities of the monitor I could quickly throw into the test setup. The screen still reported correct frequencies on the out of range message so it seems these modes were ok as well. However, I noticed OSSC reported the mode as 375p* (on info screen) where the asterisk means sync uses constant even field indicator which is a major issue for the video ADC. Usually things work when the source is booted in a more standard mode, but sync detection issues may sometime occur despite that. 240p from GC does not inhibit this sync feature - I wonder if this is something that could be controlled by SW?

[RocketBelt]

I'm having a problem with Dreamcast. Its a pal dreamcast connected via a blaze branded vga box. It works with the default settings, but at the wrong aspect ratio (slightly too narrow in the horizontal)
When I select DTV 480p in the sampling options, I can see that the picture changes to the correct aspect ratio, but it also loses sync (the light on the ossc turns red) every one or two seconds. So I can only see the picture for a few moments every few seconds. When i turn sapmling options back to auto or vesa it works fine again, and never loses sync.
Am I missing something? Is there some other setting I should try? Bad cable? I reset all settings to defaults on the ossc just in case, and checked the wiki but couldn't find anything.

[Fudoh]

When I select DTV 480p in the sampling options, I can see that the picture changes to the correct aspect ratio

This should not be happening with the standard settings. DTV is supposed to give you proper sampling at an even narrower aspect ratio. The reason for this is that the DC outputs 4:3 with black bars on the sides (640 active pixels on 720px total "visible" width). You can change the AR by re-defining the active output area, but this alters the timing and is what's probably causing the imcompatibilities on your setup.

[RocketBelt]

Thanks for the reply, I think the junkerhq wiki is causing me some confusion as it says setting DTV 480p will correct the aspect ratio issue.
http://junkerhq.net/xrgb/index.php?titl ... c_settings
My ossc is also going through a VP50 and I didn't check if I left any positive h-scale in those settings for this input type. So I need to check my set up here.

Is there a set of instructions somewhere as to what settings I need to change in the ossc to get the correct aspect ratio for dreamcast? I know in your post you say I need to re-define the active output area. Is this 'Horizontal/Vertical active length' in the active timing tweaker?

[Fudoh]

To alter the aspect ratio you basically reduce the horizontal active length while increasing the other portions (front/back porch) at the same time, trying to make your display see a 640x480p signal intead of a 480p (DTV, 720x480p) one. There's absolutely no need to do this though, when you're running through a DVDO anyway, since you can control the AR on there as well. Unless you're using the OSSC to double to 960p there's actually no reason at all to run through the OSSC. Your VP50 works with a 480p HDMI signal just as well as with a 480p RGBHV one directly from your DC.

But since you see your OSSC's input lock actually dropping, this is not your issue. Switching the OSSC's input sampling between VESA and DTV shouldn't change how the OSSC reacts to the signal. Not sure what's going on there. Maybe try the other available sync options.

[marqs]

But since you see your OSSC's input lock actually dropping, this is not your issue. Switching the OSSC's input sampling between VESA and DTV shouldn't change how the OSSC reacts to the signal. Not sure what's going on there. Maybe try the other available sync options.

Changing sampling rate actually can change things due to yet another issue with the video ADC. It requires HV sync to have sync edges closely aligned, and the distance apparently is counted in samples internally so smaller samplerate is more likely to meet the threshold requirement. I probably should try bypassing raw VSYNC to FPGA and do all detection and realignment there since the ADC's sync processing is not robust enough.

[RocketBelt]

Thanks Fudoh and marqs for your thoughts. I think because nobody else has reported this, I will guess that the issue is with my hardware, either the VGA box or VGA cable. If you do make a change in future I'd be happy to test DTV mode again with the same set up.

Right now, VESA mode or Auto mode works 100% stable for me. I correct the aspect ratio using a VP50. I can also plug my Dreamcast directly into the VP50. I just wanted to try out this DTV aspect ratio fix for the Dreamcast to see if I could get the image slightly sharper.

[Fudoh]

I just wanted to try out this DTV aspect ratio fix for the Dreamcast to see if I could get the image slightly sharper.

VESA setting on the OSSC results in a loss of resolution. DTV or directly connecting to the VP50 is fine and gives you the full resolution. You can easily see this, if you bring up a 1-px checkerboard pattern either from the 240p test suite or from a game (like Guily Gear X).

[RocketBelt]

Ah ok I did not know that. I have a test suite disc burned already so I'll give that a try tonight. I didn't know the VP50 preserved the resolution.
Thanks for the tip.

[Fudoh]

I didn't know the VP50 preserved the resolution.

I haven't used it in ages. When you bring up the info screen, it should tell you whether it sees the input as VESA 640x480p (which is wrong) or SMPTE 480p (which is correct with 720px horizontal res).

If you run through the OSSC first and then via HDMI into the VP50 you can check the same info screen to see how the sampling setting on the OSSC changes the output or how any change in the active horizontal length setting changes the recognition on the sink's side (the VP50 in your case).

[RocketBelt]

Through the ossc in vesa mode, the VP50 reports vga-60hz.
Through the ossc in dtv mode (sync was stable for a few seconds so I could get the info screen and a photo), the VP50 reports 480p-60hz.
Directly into the VP50 analogue bnc connectors, the VP50 reports vga-60hz.

I also tried a different vga cable to see if I could get the dreamcast and ossc to sync in dtv mode but it was no difference. I wonder if it is because I'm using a PAL console and if it has slightly different timings. I read that the PAL PS2 has slightly different timings for 60hz output. The dreamcast and vga box are not modified in any way, I owned both from new.

I did try the 1px pattern in the test suite, and while that is slightly soft in vesa mode, the actual picture when playing a game is still very nice, either through the ossc or directly into the VP50.

Still, if there is any change to dtv mode and syncing in future I'd be happy to try it out again.

[Fudoh]

Directly into the VP50 analogue bnc connectors, the VP50 reports vga-60hz.

thank you for testing this. I might mis-remember how it worked on the DVDO. Or this was improved on the VP50Pro. If you're not bothered by the artefacts introduced by applying the wrong sample rate, by all means, please be happy with it.

[fandangos]

Need some help, my OSSC works without any problem on any digital display I have.

Now I wanted to try it with my Sony G520. I have a hdmi to vga adapter that I use all the time with my PC.
The OSSC is picking up the signals from my consoles but I don't get any image on my monitor. No signal at all.

Things I tried: Turning TX on, setting to DVI mode. All the X modes.

The adapter I'm using has no external power, can this be the cause of it not working with the OSSC?
Any help would be really appreciated.

Thank you.

[ldeveraux]

The adapter I'm using has no external power, can this be the cause of it not working with the OSSC?

This is likely it here. I tried to do something similar, converting hdmi to vga, and I used a quality powered adapter to get signal. I used this: https://www.amazon.com/gp/product/B07C8CMC4Z. Granted this was from a KVM to a TV, but should still apply?

[fandangos]

I might give this a go.
Because of the pandemic it's been quite hard to find imported goodies but it's a good thing my suspicion was correct.

[marqs]

The adapter I'm using has no external power, can this be the cause of it not working with the OSSC?

What is its specified current draw? There's a 200mA polyfuse on DDC5V line which temporarily opens if a connected peripheral draws more current. You should also try setting "Default HDMI VIC" to 2 - some badly designed switches/adapters require an explicit VIC to work with anything.

[fandangos]

The adapter I'm using has no external power, can this be the cause of it not working with the OSSC?

What is its specified current draw? There's a 200mA polyfuse on DDC5V line which temporarily opens if a connected peripheral draws more current. You should also try setting "Default HDMI VIC" to 2 - some badly designed switches/adapters require an explicit VIC to work with anything.

no go.
Just ordered another cheap one that can take 5v.
I'll report if the new one does work.

[fandangos]

Received a powered hdmi to vga adapter. No signal.

maybe my monitor is picky about signal, no idea.
Tried every settings and no difference.

[Extrems]

I just checked GBI on my setup (official component cable) and didn't bump into sync detection problems. Line2x and Line2x 240x360 displayed without issues, passthru and Line3x 240x360 were beoynd capabilities of the monitor I could quickly throw into the test setup. The screen still reported correct frequencies on the out of range message so it seems these modes were ok as well. However, I noticed OSSC reported the mode as 375p* (on info screen) where the asterisk means sync uses constant even field indicator which is a major issue for the video ADC. Usually things work when the source is booted in a more standard mode, but sync detection issues may sometime occur despite that. 240p from GC does not inhibit this sync feature - I wonder if this is something that could be controlled by SW?

Unfortunately, resolving that did not help.

Hmm, I got it to work by increasing Vsync threshold to 14.76 us.

[naz]

Hi,

Just wanted to check if I'm doing something wrong with my ossc:

- I turn on the ossc and a console, everything is fine.
- I press reset on the console and the image shows a bit of vertical wave.
- I turn off and on the ossc and everything is fine again (no wave).

The above happens every time. Am I missing a setting?? is this a normal sync issue?

[bobrocks95]

I just checked GBI on my setup (official component cable) and didn't bump into sync detection problems. Line2x and Line2x 240x360 displayed without issues, passthru and Line3x 240x360 were beoynd capabilities of the monitor I could quickly throw into the test setup. The screen still reported correct frequencies on the out of range message so it seems these modes were ok as well. However, I noticed OSSC reported the mode as 375p* (on info screen) where the asterisk means sync uses constant even field indicator which is a major issue for the video ADC. Usually things work when the source is booted in a more standard mode, but sync detection issues may sometime occur despite that. 240p from GC does not inhibit this sync feature - I wonder if this is something that could be controlled by SW?

Unfortunately, resolving that did not help.

Hmm, I got it to work by increasing Vsync threshold to 14.76 us.

One step above 14.76 worked for me, 14.76 was a bit shaky. Looks wonderful though, doing hdcustom with 360px3 and H. Samplerate at 302.

[strayan]

Received a powered hdmi to vga adapter. No signal.

maybe my monitor is picky about signal, no idea.
Tried every settings and no difference.

HDMI adapters have been hit and miss for me. The only one I have found which works reliably with all my sources (don’t have an OSSC to test unfortunately) is this: https://www.ugreen.com/products/hdmi-to ... c725&_ss=r

YMMV obviously.

[marqs]

Firmware v0.86 has been released. Nothing major this time but a number of small improvements that have been included over the last 7 months:

Analog frontend updates
* Added STC LPF option
* Added clamp/ALC options

Compatibility updates
* Improved 576p / 800x600 detection
* Updated AV3 alternative RGB compatibility option
* Added 480x272 sampling mode for PSP
* Optimizations to support higher pixel clock output

[nullifer]

Can someone explain in which situations it would make sense for me to update to this firmware? (typically i understand the changes, this time no)

[RocketBelt]

Can someone explain in which situations it would make sense for me to update to this firmware? (typically i understand the changes, this time no)

It looks like the ossc wiki has been updated as well and the answers are there.

[Konsolkongen]

Could Sl. alt interval be disabled for 240p content? I use it often for linedoubled Dreamcast games, but when outputting real 240p as required by some games you only get half the scanlines with this option still enabled. Would save us the trouble of toggling the option in the menu

[Lawfer]

* Added 480x272 sampling mode for PSP

What does that mean? And doesn't the PSP Output in 720x480 when outputting to a TV?

[headlesshobbs]

Here is the PSP page with v0.86 for reference. http://junkerhq.net/xrgb/index.php?titl ... n_Portable

[Unseen]

What does that mean? And doesn't the PSP Output in 720x480 when outputting to a TV?

The PSP outputs a 480 line progressive signal (though I'm not sure about the horizontal pixels right now), but when running a PSP game, it only occupies the central 480x272 portion of the picture.

[Fudoh]

that's neat. I wouldn't have expected the OSSC to be able to handle this (= increasing the vertical back porch this this degree).
This just leaves the question what to do with that 540p output signal. Probably not compatible with too many devices.

So far OSSC > Extron (301) was a pretty good solution, since the Extron let's you define the active picture as well, so it was easy to just define the 960x544p area as the active input. The DVDOs can do the same with 960p input, but defining the active area is bit less "scientific" and the 4:2:2 processing makes the picture a little less vibrant compared to the 4:4:4 scaling on the Extron.

Unfortunately 3x/4x on the OSSC isn't possible due to the the complete vertical pixel count of the input signal (well, a 480p signal after all). The XRGB-3 as of now remains the only processor to sample the picture properly AND apply 4x integer scale. OSSC Pro please, thanks!