Advanced timing settings for Amiga

[BuckoA51]

looks like it would do the job, but doesn’t seem to say where you’d buy it from.

[jdryyz]

I noticed that too. I think he has a separate ordering page somewhere (possibly eBay) or it is not available quite yet.

[jarp]

I contacted him, he was willing to sell boards to me. If you are not in hurry, wait a while, I’ll report if the board works well with the OSSC or not after I get it. I guess that it is buffered no doubt so that will not be a problem, but dunno if it uses schmitt trigger as well and if that matters or not…

[jdryyz]

Thanks! I’m not in a hurry. 🙂

[jarp]

Boards from retro.68k.pl arived. I can confirm that “AMIGA RGB TO BUFFERED VGA, COMPOSITE AND S-VIDEO” works well with the OSSC. All screenmodes I tried worked well including productivity. I did not try composite or s-video but those are nice options as well. Build quality seems to be very good as well, so I can recommend this setup with the OSSC.

[jdryyz]

Great! Thanks for sharing.

[jdryyz]

Just received my OSSC today (fw 0.78a)

Sooo…..anyone using this successfully with a Dell U2410? I am using the SCART input on the OSSC and the HDMI out to the Dell. My Amiga 1200 is connected using an RGB to SCART cable. When the OSSC is powered on, I see the test pattern just fine. When my Amiga is powered on, the OSSC reports a 263p signal @ 15.73KHz, 59.82Hz but I am not seeing an image displayed. I tried toggling thru the line modes and even tried PassThru but I do not see an image. My Amiga 1200’s Workbench is set to Dbl PAL Hi Res NO FLICKER but I initially just tried to boot from a simple Workbench floppy. The screenmode is default NTSC (might be interlaced, I’m not sure). When I did let it boot to the AGA screenmode from the mass storage, I got an out of range message on the Dell.

I am thinking the Dell might be picky about what comes across over HDMI, even though I am sure I used a Windows PC with an HDMI graphics card attached in the past with no trouble. Maybe I will try an HDMI to DVI cable next.

[jdryyz]

Fortunately, I have another A1200 setup I can use for testing. This is a bare-bones PAL A1200. It has a Compact Flash OS 3.1 system but no FAST RAM. The OSSC seems to do a better job recognizing a PAL-based system (at least when it comes to Amigas). My Workbench is on a PAL Hi Res screen and it came up just fine. From here, I was able to test the line doubling modes and scanlines. The TV for this setup is a Vizio M60-C3. Prior to the OSSC being connected, I was using a cheapy SCART to HDMI converter. As was anticipated, the OSSC output is superior and has none on the motion artifacts seen with the converter. Scanlines set to auto seems to give the best results. Line 3x & 4x do not appear to be compatible. Line 5x works and is reported as 1080p. However, it is overscanned beyond usable. I suspect this can be compensated for in the menu settings, but it since Line 2x looks just fine to me, I see no reason to change it for this setup.

Getting back to my NTSC A1200. Since I discovered the OSSC is syncing better with PAL, I booted the the computer holding down the mouse buttons to access the early start menu. I hit a key on the keyboard to toggle to PAL. Sure enough, an image appeared. I made some minor monitor adjustments to brightness and then increased the scanlines to 12x. This gave better results with this display. I tried toggling back to NTSC and was surprised to see the display worked! I could toggle PAL/NTSC while in the menu and the OSSC is able to sync just fine. Conclusion is that there is an initial sync problem with an NTSC system? For the curious, the PAL mode that the OSSC accepts is 313p 15.73 KHz. 50.26 Hz. I noticed that when my NTSC A200 is in PAL mode, the output differs from the one in Todd’s video:

He is also using a PAL A1200. I failed to note what results I got with my true PAL A1200. Perhaps the difference could be the fact that my NTSC A1200 has an ‘030 accelerator installed or just because I am using software mode change?

I kinda new I would have trouble with other Amiga screenmodes but I was surprised to see interlaced screens flickering as bad as they did (tested on the PAL machine). It mimics what a CRT does a bit too good but I suspect interlaced screens that are actually in games & demos may not look as bad. Despite getting the NTSC screen to show up, I could not make Dbl PAL Hi Res NO FLICKER work with any setup or even with PassThru selected for the Dell. Note that this works fine with the VGA adapter and no OSSC.

So should I return my VGA adapter to the A1200 and give the OSSC’s VGA input a try?

[marqs]

If you press ‘INFO’ on remote while in NTSC mode, what is the value of VSM? Also, have you tried setting HPLL pre&post coast to 3 in sync menu?

[jdryyz]

Hi marqs!

VSM value in PAL mode = 0, VSM value in NTSC = 2.

I will try your suggestion on the H-PLL settings…..sorry, it did not help. It still syncs to NTSC once the PAL screen is up, though. Just not on a cold boot.

I see there are many settings in the menus I no nothing about! 🙂

I should mention switching to the VGA input did help with the PAL/NTSC syncing. In addition, I am able to use Dbl PAL Hi Res NO FLICKER. Thanks to jarp’s post, much time was saved adjusting the settings, although I had to do my own tweaking to get it just right. Unfortunately, there are negatives using the VGA input: 1) I still get the vertical banding in the NO FLICKER mode (no surprise). 2) There are some noisy patterns that appear in PAL Hi Res (even after jarps settings). It looks a lot like RF interference. It seems to be related to the H.samplerate setting. Without changing to the recommended setting, however, text looks bad. NTSC is rock solid in comparison.

I have none of these problems using the SCART input. Too bad I am not only using PAL & NTSC. I have gotten used to the increased real estate of the Dbl PAL Hi Res NO FLICKER mode and prefer it for everything else.

[jarp]

My 5 cents again… It’s highly likely that SCART cable is unbuffered, hence not optimal. I had troubles with SCART cable and any other mode than PAL. For some reason PAL worked, others did not. Your VGA adapter, I do not know if it’s buffered or not, but buffered VGA adapter helped a lot for me. But since you have NTSC machine, that adapter from retro68k does not work with them.

Also I think you are expecting too much. Most likely there will be vertical banding always and nothing you can do about it when using external scandoubler. Keep in mind that what you have there is consumer grade product from early 80s made as cheap as possible – no way video out would be without analog artifacts. In real life, in real use cases, vertical banding most likely goes unnoticed. I only notice it when screen is black and stationary.

Noise patterns, I think it has something to do with sampling phase algorithm which is not perfect in the OSSC or something like that. There were some discussion on the other forums about it. When you use “wrong” H. samplerate there won’t be noise anymore because OSSC no longer syncs perfectly to outputted pixels. Again, when you set samnpling phase correctly, noise is hard to notice in real life scenarios.

Of course I am talking about my Amiga only, if yours have more visible banding then it may be different case.

[BuckoA51]

Also PAL Amiga’s clock is well off-spec when forced into NTSC this can cause problems with some displays.

I kinda new I would have trouble with other Amiga screenmodes but I was surprised to see interlaced screens flickering as bad as they did (tested on the PAL machine). It mimics what a CRT does a bit too good but I suspect interlaced screens that are actually in games & demos may not look as bad.

It’s not that OSSC is intentionally mimicking a CRT here, it’s that it’s the only way a device without a frame-buffer can deinterlace. If you pass through the interlace signal your display (if compatible) will do a better job, but of course with input lag.

I have gotten used to the increased real estate of the Dbl PAL Hi Res NO FLICKER

Double PAL is kind of a weird mode, can you try double NTSC instead? I have a feeling it’s because you’re feeding in a 50hz 31khz mode which is not compatible with a lot of things.

[marqs]

VSM value in PAL mode = 0, VSM value in NTSC = 2.

Non-interlaced sources with odd field flagging (VSM=2) are problematic for the digitizer chip which explains your behavior. A workaround is to temporarily switch to a non-interlaced mode with even field flagging (VSM=0) or to an interlaced mode (PAL and NTSC both fine). VGA is another option (H+V or C sync) but it has other drawbacks.

[Norpa76]

Here are my PAL LowRes settings for 1350×1080 resolution that has 5:4 aspect ratio. Monitor needs to have 5:4 AR setting to get square pixels.
Since PAL 320×256 has 5:4 AR these settings will give perfect image for gaming with little bit of overscan.

240p/288p lineX4: On
H. samplerate: 1800
H. active: 1350
V. active: 270
Use H. and V. backporch settings to center the picture.

[jdryyz]

Thanks everyone for your help. It has been a busy week for me so I have not had time to revisit the OSSC yet. I will try this weekend.

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