Anyone using an OSSC (Open Source Scan Converter)?

[Tom Wilson]

I've started playing around with an OSSC to convert my Altairduino Pro directly to HDMI, and bypass needing a VGA monitor, since my VGA monitor simply won't handle the terminal board's signal.

I was a little surprised at how far out of spec the VGA output was. By the time I finally got a viewable frame with no blurring and moiré effects, my settings looked like:

H. Sample Rate: 635

H. Synclen: 91

H. Backporch: 14

H. Active: 488

V. synclen: 2

V. backporch: 51

V. active: 440

So accounting for the 4x4 border I dialed in, to allow me to align the edges, this makes the actual resolution of the terminal 480 x 432, with a character cell size of 6x18

If I was to dial out the edges and lose the 4x4 border, I'd use:

H. Sample Rate: 635

H. Synclen: 91

H. Backporch: 18

H. Active: 480

V. synclen: 2

V. backporch: 55

V. active: 432

What's interesting about this is that this scales to a relatively clean 2.5x on a 1080P monitor, which makes the image look pretty good on my HP monitor.

Has anyone else tried their AD Pro with an advanced scaler? What kind of results have you had? 

[Tom Wilson]

> interesting as i never had any issues with the VGA monitor using a LCD or a CRT

Actually, the AD does work on my HP monitor. For some reason, the terminal board was just acting wonky when I tried it previously. I also got a 15KHz scan rate on the OSSC, so I'm wondering if turning on the Altair without the VGA cable plugged in put the terminal in NTSC mode. 

Regardless, the image quality of the OSSC vs the internal scaler on the HP is very different. The HP's output is fuzzy when using the built in VGA port, but it's perfectly crisp using the OSSC. That's actually one of the nice features of the OSSC; it samples and regenerates pixels, often producing a better image than the original.

Anyway, I haven't done much more with the scaler, after that. I got the terminal working on my PC again, and I discovered a new, interesting quirk in the emulator's serial I/O (which I'm going to talk about in another post.)

On Sunday, October 13, 2024 at 7:33:28 PM UTC-7 John Galt wrote:

interesting as i never had any issues with the VGA monitor using a LCD or a CRT. 

you sure there isn't something wrong with the terminal board your using?

In the last 4 years i have used various LCD and CRT monitors with no issues. i went though the original GEOFF terminal that the Pro comes with but eventually settled into using the FABGL ANSI Terminal since it has 64 colors and full VT-100 support.