Tips & Tweaks: Lx3, Lx4, Lx5 modes

[funny_mikey]

Well unfortunately I was not able to get lx5 working. I was able to get the picture scaled to fit into the box horizontally though. I followed the steps for adjusting v.active to 256 and then adjusting v.backporch down to 3 which is where my TV will get an image. Next I aligned the text until sharp and then I hit a snag. For some reason I cannot adjust v.active back down to 240. I lose the image no matter what I try to adjust. This is in both generic 4:3 and 256×324 optim. What I’m left with is an image that is just a tiny bit too large to fit horizontally so it cuts off the image a bit on 1 side or the other and then I have black bars above the image but they’re not even. It still looks better than being framed all the way around so Im making some progress. I’ll try lx3 tomorrow and see if I have better luck.

[HDL]

Just updated my firmware and am trying line x5. I can get an almost perfect picture if I set the mode to 1920×1200 (although my display is 1920×1080). I have H.active set to 348 (native Genesis width plus the overscan area) and this appears correctly on my screen, but I can’t find the H.samplerate sweet spot at all. I can’t make heads or tails of those spreadsheets and I don’t otherwise know how to calculate what these values should be. My monitor is an AOC G2460PF.

[Harrumph]

I assume you mean for optimized mode? Optimized output should be 427 for Genesis, but it also uses 256×224 mode for some games, in which case the output is 341. Remember you also have to adjust sample phase.
If you use generic mode instead, the output should be a multiple of 390.

[HDL]

Yeah it’s for optimized mode. I am testing with games that output 320×224 as well as the 240p Test Suite using the 320×224 grid. Adjusting the sample phase I can get very close but no cigar. At a quick glance it looks perfectly clear, but upon scrutinizing it there is always a slight amount of blur on one side. Low degree values give a very slight blur on the left and high ones on the right. This is a matte display, by the way.

For normal gameplay it looks perfect, however I plan to record with this setup eventually and would rather eliminate all traces of blurring if possible.

Here are my values, in case they help anyone:

Sample phase 112
H.samplerate 427
H.synclen 38
H.active 348
V.active 240
H.backporch 33
V.backporch 18
Line x5 using 1920×1200 mode.

Edit: Actually upon checking the linearity test it seems 1920×1200 stretches the image to non-square pixels. 1920×1080 keeps them square but won’t display the entire image using line x5.

[marqs]

@Harrumph: added MD parameters to optimal timings wikipage. What’s the reasoning behind multiple of 390 for generic modes btw? Is the purpose to keep it far enough from both 341 and 427 to minimize the number of unsharp/jittery columns?

@HDL: There should be no difference in aspect between 1920×1080 and 1920×1200 modes unless your display applies some streching.

[Harrumph]

Haha, it’s a bit funny that you ask because the numbers actually derive from your default x3/x4 settings from the beginning! So I would have asked the same of you, originally, but then I started sort of “reverse engineer” it to try and figure it out for myself… 🙂

Now, just a disclaimer I am not an engineer or such and I just recently got interested in this analog video signal stuff because of the OSSC. Wanting to inform myself, and possibly help others, I did quite some research trying to figure out why certain sample rates worked on my displays, and this is how it makes sense to me… But maybe my explanation is not entirely correct.

My conclusion was that the reason behind 390 should be pixel aspect ratio (PAR) correction, to achieve correct display aspect ratio (DAR) when mapped to the 1:1 PAR fixed pixels of modern displays (with 480p as a notable exception). I got my info on PAR from this page.

PAR for 256 active width dot clocks (5.37 MHz, SNES etc) is 8:7, and 341*(8/7)= 389.7.
PAR for 320 active width dot clocks (6.71 MHz, Genesis & PSX) is 32:35, and 427*(32/35)= 390.4.

(And btw the actual aspect ratio of graphical content is not 4:3 but ~1.306, but I think I’ll leave that for another post…)

[funny_mikey]

So small update. I upgraded the firmware in my TV, changed the input name to DVi devices, disabled anything in the TV settings that looked like it could interfere, and played with the Adv timing and now I’m getting signs of lx5 support. The image flickers but can’t seem to stabilize for more than a second or two (just long enough for game audio to be heard briefly). Is there some combination of settings I could possibly adjust to stabilize the image?

Edit: I have a stable image in Lx5! I had to disable “Allow tvp hpll2x”. Just like with the other outputs I cant seem to get the correct aspect ratio. Also I have a tear running up the middle of my screen that won’t go away. Not sure what’s up with that.

[Trixster]

Has anyone had any success in getting a Panasonic GT50 tv working in lx3 lx4 or lx5 mode?!?

[fyrabanks]

Perhaps a weirdly specific question, but has anybody else experienced any issues running SNES Chrono Trigger in x4 or x5 mode? x3 works just fine, and my monitor’s able to display any other game at x4 and x5 (without any tweaking), but I just get a black screen with CT.

[ranho]

Dear all thank you for all your contributions and maybe more experienced people can help me out.

I own a Panasonic Viera TX-L32E6B, already with a few years, that I use only to play, it is quite good and if someone wants a tv that upscales 240p quite nicely this is an option in the second hand market, in fact I was quite impressed by the quality of the upscaling once I saw line doubling with the OSSC.

This leads me to my cry for help, I can’t do any LX3 or higher and would be thankful for tips. I tried everything single config someone posted in this thread, but I couldn’t make it work, the image is just black, the only info I have on the TV is this:
HDMI terminal Valid input signal format
525 (480) / 60i, 60p
625 (576) / 50i, 50p
750 (720) / 60p, 50p
1,125 (1,080) / 60i, 50i
1,125 (1,080) / 60p, 50p, 24p

Because it accepts 720 I thought I was gold! But I can’t see anything.

If someone has some tips I would appreciate.

[Harrumph]

I think you are out of luck. The TV does not seem to support any PC mode (I double checked the manual also). And as stated, the accepted line count for 720p is 750, while output from OSSC in Lx3 will be mimimum 786 (262×3).

[ranho]

Cheers Harrumph, I can only hope for some tweaks with firmware updates as I am not really thinking of buying a new TV.

[Gummi]

@Trixster

Has anyone had any success in getting a Panasonic GT50 tv working in lx3 lx4 or lx5 mode?!?

I’ve got the GT60, what has been your experience with the OSSC on the GT50? Is it the European model or the US model? I’ve got the Europe one myself, and I know the US and European ones don’t function the same despite being the same model. Did you ever get modes over 240p x2 working? If not, did you try and see if BonzoBits’ adjustments worked on your tv? He has a VT60, though probably the US model, but I was hoping it might work on the GT60 too in case it doesn’t already support those modes.

If you could please add your experience with your TV to the compatibility list, that would be very helpful to me and other prospective OSSC owners, even if your TV is one generation behind mine.

[Harrumph]

I wouldn’t get my hopes up. 🙁
You didn’t specify model number, but I checked the manual of TX-P50GT60B. Similarly to ranho’s Panasonic a couple posts above, it only lists 750 line compatibility, and no PC modes.
We won’t know for sure until you (or someone else) can actually test it.

[Trixster]

I have tried some of those settings on my Euro GT50 and I can’t get 3x or 4x to work. That’s not to say those mode can’t be gotten to work, just that I haven’t been able to work them. It’s correct to say that the gt50 does not support pc modes other than 1920×1080, 1280×720 and 640×480.

Other than that the gt50 is great with lots of consoles in 2x mode. With 0.76 pal PS1 games work with slightly tweaked 288p setting but with 0.77/0.78 those tweaks no longer work for some reason

[Author]

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