How to center image of retroarch with PI outputing 240p rgb via hat board/gert 666 to pvm?

rig

@Dochartaigh yeah if its cut off on all sides I would try a value of 10 on all values"top" "bottom"" LT" "RT"

Molhoy

@rig Thanks for the feedback and your experiences with the overscan function. Also interesting to hear feedback from others too.

I have since tried it on my set up and used the following values: -

overscan_left=20
overscan_right=-20
overscan_top=-10
overscan_bottom=10

Bizarrely, the changes had exactly the desired effect... but only on the initial screen when the 3 x raspberry logos are shown, then on the initial Retropie screen with the Retropie logo, and then only on the game launch screen (the one that says which emulator is loading and gives the screen prompt to press a button to change the config for the game that's being loaded).

In all other situations - i.e. in the Retropie menus and, crucially, in game, the screen position defaults to the same as before I altered the overscan values.

What on earth is going on there?!

On a more positive note, doing the above seemed to have no negative effect on the image quality - i.e. it did not scale the image, only reposition it (albeit only in the limited situations above). I assume this is because I entered same value + and - figures for the left/right and up/down values - i.e. +20 left, -20 right. I haven't tried it, but I assume that if you alter one value but don't compensate on the opposite side, it will scale the image and produce unwanted artifacts.

In any event, I'm deeply puzzled as to why the overscan settings only work on the boot screens.

Colour me confused!

dankcushions

@Molhoy
try overscan_scale = 1 in addition to those settings.

Molhoy

@dankcushions Thanks for the suggestion.

The good news is that this now means that my overscan values work on everything including all menus and games.

The bad news is that this is producing scaling artifacts, despite my entering the same value + and - figures for the left/right and up/down parameters as described above. I guess this is what maxriptide was experiencing.

The problem seems to stem from the fact that negative values have no effect, as described by rig.

To be clear, I tried this with disable_overscan both on and off, with apparently no difference between the two.

This reaffirms my belief that it's the timings that are at fault.

As a matter of interest, I've also tried it on my Sony consumer CRT (model KV-21LS30U) and the picture is centered in a very similar fashion to my Megadrive, which is obviously very different to the experience I'm having with my PVM. I can't imagine why this would be, but just thought I'd mention it.

Back to the drawing board!

rig

@Molhoy have you tried my timings? there are a couple different ones you can choose from. They are listed at the beginning of this topic. Maybe we can try other people's timings until we find one that works

Molhoy

@rig I've tried a few different timings, including a couple from your list (which I'd already got from the RetroRGB website).

The ones I've tried are: -

hdmi_timings=320 1 16 30 34 240 1 2 3 22 0 0 0 60 0 6400000 1 (from ArcadeForge)
Image is pushed too far left and low. Also bows out slightly at the bottom of the screen.

hdmi_timings=320 1 25 30 30 240 1 9 3 10 0 0 0 60 0 6400000 1 (from maxriptide)
Image is pushed even further left, but this time is too high.

hdmi_timings=320 1 20 29 35 224 1 10 14 16 0 0 0 60 0 6400000 1 (from RetroRGB, also on your list above)
Image is pushed too far left and low, similar to the first set of timings. Bows out at the top of the screen.

hdmi_timings=320 1 14 46 28 256 1 17 32 9 0 0 0 50 0 6400000 1 (PAL Amiga resolution, from RetroRGB, also on your list above)
Image is once again pushed too far left and low, also significantly warped in top half of screen. Unusable.

The bowing/warping/geometric abnormalities are strange and not something I experience on real hardware. Obviously it's related to the timings somehow, but just adds a further layer of complication to finding the best set of timings!

I'll update you if/when I try anymore.

rig

Thanks for the update. I haven't tried anything lately. I gave up on it for a while so I could play some games. But I plan to work on it again later. I haven' tried out any other of my own timings, I think I will start there. I noticed that I had the same geometry issues on two different pvms. This makes me think that it's something idiosyncratic to each individual pie. We could try a different pie and keep everything else the same. I might try this. I have been thinking about getting another pie anyways for watching movies with my other pvm. Have you tried your pie on a deferent monitor?
How do you like your pvm 20m2mde? I have an opportunity to buy one right now, the specs look similar to my 20m2mdu which has a pretty soft image (not ideal for gaming)

Molhoy

@rig Heh heh, now you've started me off on something...

In answer to your question, the only other CRT I've tried with the pie is a Sony consumer CRT - model KV-21LS30U. On that, the image is pretty much perfectly centered and is essentially in the same 'ball park' as all my other systems, whereas on my PVM the centering of my Pie image is miles away from everything else. It's a total mystery to me.

I've become a bit of a CRT obsessive over the last 12 months. I've tried lots of PVMs and consumer CRTs. At the risk of boring you, these include: -

PVM20L2 - 600 line, high contrast tube. Nice inky blacks, but image too soft and suffered from horizontal banding on light colours. Colours generally more muted than the other monitors I've tried, regardless of settings. I've tried several 20L2 and all are the same.

PVM20M2E - 600 line, high contrast tube. Again, nice inky blacks and sharper image than the 20L2. A good monitor, although mine had some geometry issues that couldn't be corrected from the service menu (main issue being a tilted picture). No doubt a good example would be a good, solid choice of monitor.

PVM20M4E - 800 line, lower contrast tube. Like all 800+ line PVM/BVMs, this has a lighter-coloured tube, meaning that true blacks are harder to achieve. No one ever seems to mention this, but for me this is a major drawback of all the 'HR Trinition' PVMs and BVMs. Conversely, this is the sharpest monitor I've tried - almost too sharp, meaning it looked less like an authentic CRT picture and was more reminiscent of emulated scanlines.

PVM20M2MDE - 600 line, high contrast tube. This is my current monitor and as you would expect, this is similar to the 20M2E I had, only it's newer and therefore has a brighter, sharper picture. Also, being the medical model it has 2 x RGB inputs, which is a nice bonus. This is the best monitor I've had so far.

I've tested others, but these are the main ones. For me, the 600 line monitors with the higher contrast tubes produce a more pleasing and 'authentic' picture than the 800+ line monitors - hitting the sweet spot for detail and contrast. I've never actually used a BVM, but suspect these would not suit my tastes for the same reasons I didn't like the 20M4E.

The consumer CRTs still interest me as for obvious reasons they provide the most authentic retro picture of all. The KV-21LS30U is a particularly nice example as it has the FD Trinition flat tube, which in my experience produces excellent geometry for a CRT.

I'll shut up now before I send everyone to sleep... bet you wish you hadn't asked!

Molhoy

@rig Hey man, I think I've cracked it...!!

I joined the Facebook group for Arcadeforge, where I bought my pi2scart. There I found a set of timings that solved my vertical position: -

hdmi_timings= 320 1 22 20 42 240 1 6 8 10 0 0 0 60 0 6400000 1

However, these are pushed even more to the left. But... and this is the important bit... I found a post from a great guy on there (Frank Skilton), which specifically explained how to alter the hdmi timings to reposition the picture: -

To shift the image left, increase the horizontal front porch while decreasing the horizontal back porch by an equal amount. Do the opposite to shift right.

To shift the image up, increase the vertical front porch while decreasing the vertical back porch by an equal amount. Do the opposite to shift down.

3rd parameter is horizontal front porch
5th parameter is horizontal back porch
8th parameter is vertical front porch
10th parameter is vertical back porch

So, in the case of the above timings, I was able to reduce the horizontal front porch by 12 and increase the horizontal back porch by 12 to shift the image right and perfectly centre it on my PVM.

See below (changed values highlighted in bold): -

before: hdmi_timings= 320 1 22 20 42 240 1 6 8 10 0 0 0 60 0 6400000 1
after: hdmi_timings= 320 1 10 20 54 240 1 6 8 10 0 0 0 60 0 6400000 1

These now give me a perfectly centred image!

While these may or may not work for you, hopefully the above explanation will allow you to manipulate your timings to achieve the perfect result.

I hope this helps!

rig

Molhoy, awesome! good explanation on the hdmi timings. I'm picking up what your putting down. I will try this out on Monday when I'm off work...

I'm a bit of a crt nutter myself. Thanks for sharing the info on the monitors. A couple of things you mentioned are interesting to me: You mentioned that the 800 line monitor is too sharp. I have been hopeing too pick up a 800 line monitor but maybe this wouldn't be worth it. I have noticed when watching videos of bvms that the scanlines can look too pronounced. I can tell you that pardoxically my 560 line pvm 2030 looks sharper and darker than my 600 line pvm 20m2mdu. and the 2030 has way more miles on it (it's geometry is a bit whack in the corners but It gives it character). The 2030 also has a bit of a sideways caddywompum to it, I adjusted it a little with the pots and I set a piece of wood under one side of it and now the slant is completely gone. Have no idea why the beat up old 560 line 2030 outshines the 20m2mdu...the 2030 was built in 1992 (if I remember correctly) and the 20m2mdu in 2001...Maybe it's cause I rescured the 2030 from the dumpster. 2030 better putout them scanlines or it's going back were I found it mwahahaha

maxriptide

@Molhoy this info about timings is great! Thank you!!!

Molhoy

@rig Yeah, these CRTs are addictive!

Of course, my opinion is very much my own, so don't necessarily let it put you off the idea of an 800 line (or higher) monitor. I've just reached the conclusion that they don't suit my tastes.

I had the opportunity to buy a 2130 (uk version of the 2030) when I bought my 20M2MDE. I must say that I was very impressed with the picture, it looked very bit as sharp - if not sharper - than the 20M2MDE and the colours seemed to pop even more. However, although it was in generally excellent condition, the picture did suffer from some impurity issues (slight yellow tinge in one corner), which is a big no-no for me. Also some geometry issues that would have been hard to correct. Certainly the 2030/2130 have a good reputation and I think date back to a time when Sony were at the very top of their game, which may explain the picture still being so good even today.

Good luck with adjusting your timings. I've been playing with mine some more tonight and I'm really thrilled with it now that my picture is centered.

Let me know how you get on.

Molhoy

@maxriptide You're welcome.

I can't really take credit for it - as I mentioned, I found the solution on Facebook :)

However, I'm glad to share it with you guys and I hope it gives you the desired results!

rig

Molhoy, Problem solved! Picture is dead center. No sharpness lost. Thanks dude. I uncommented all the overscan adjustments and messed with the front porch/ back porch for about half an hour and now it's perfect. Good job persevering on this one Molhoy. You had a hunch that the problem could be solved with the timings and you were right.

Molhoy

@rig You're welcome.

Really pleased to hear that you've got your timings sorted.

It's very satisfying to finally have a perfectly sharp 240p properly centered, isn't it?!

I've been playing lots of Neo Geo stuff, which looks awesome.

Next problem to solve is dynamic resolution switching to overcome the issue of different systems being at different resolutions, but that's a whole different ball game!!

Dochartaigh

@Molhoy said in How to center image of retroarch with PI outputing 240p rgb via hat board/gert 666 to pvm?:

To shift the image left, increase the horizontal front porch while decreasing the horizontal back porch by an equal amount. Do the opposite to shift right.

To shift the image up, increase the vertical front porch while decreasing the vertical back porch by an equal amount. Do the opposite to shift down.

This is great info on how to center the image! Did they shed any light on how to SHRINK the image? (mine is actually OK centered, but definitely WAY too large).

edmaul69

@Dochartaigh overscan settings are what you have to use to fix that. Not sure why it isnt working for you.

Dochartaigh

@edmaul69 said in How to center image of retroarch with PI outputing 240p rgb via hat board/gert 666 to pvm?:

overscan settings are what you have to use to fix that. Not sure why it isnt working for you

Haven't tried overscan quite yet - just trying to get all my ducks in a row for when I have time to mess around with this again (whenever the heck that'll be I do not know lol ;)

I'm planning on balancing the porch settings of HDMI_timings for centering the picture, and will now use overscan alone to scale.

rig

@Molhoy Yeah, the display looks great. I'm glad I made the extra effort to center it. Now I can get back to gaming. I been playing games I always wanted as a kid but couldn't get because they were arcade, or on an obscure system. I'm playing aliens vs predator for arcade right now and shining force for sega cd