Turning on the borders option blurs the picture

[Former user]

Original [issue 62](https://code.google.com/p/genplus-gx/issues/detail?id=62) created by thiagoalvesdealmeida on 2010-01-13T03:20:25.000Z:

What steps will reproduce the problem? 1. Default options (display: original and "borders" turned on). 2. It happens with all games, but Sonic 1 or 2 is a good reference. 3.

What is the expected output? What do you see instead?

The picture looks a bit more blurry with borders turned on. Turning the borders off fix the problem, and you get a more sharp picture (as good as the Virtual Console).

What version of the emulator are you using?

Last stable binary release.

Please provide any additional information below (video settings, console region,...)

I'm using a 27" CRT NTSC SDTV with component cables.

[Former user]

Comment # 1 originally posted by ekeeke31 on 2010-01-13T08:02:19.000Z:

Turn bilinear filtering OFF in the Video Settings.

[Former user]

Comment # 2 originally posted by thiagoalvesdealmeida on 2010-01-13T13:10:18.000Z:

Sorry. I forgot to mention that bilinear filter was already turned off. It was my mistake: I'm not really using the default options, since I turned off the bilinear filter. So, the problem still occurs even with the bilinear filter turned off.

[Former user]

Comment # 3 originally posted by ekeeke31 on 2010-01-13T14:02:44.000Z:

Then there is not much I can do, it's due to the default Video Hardware output filtering when upscaling. It cannot be disable and is automatically applied when the rendered image width is narrower than video output width. And if I don't upscale horizontally, the aspect ratio would be wrong.

Let me explain the difference :

When borders are turned OFF, the image width is 320 pixels and therefore can be simply doubled to 640 pixels when rendering (no filtering is required when the scaling ratio is x1, x2, etc) then the Wii Video Hardware take care of the remaining upscaling to take pixel aspect ratio differences in account (I mesured that 320 'genesis' pixels approx. match 654 'Wii' pixels). The upscaling from 640 to 654 pixels requires some pixel interpolation but is not really noticable.

When borders are ON, the image is wider (352 pixels) so I cannot upscale this to 640 pixels during rendering without filtering it. Since the bilinear filter applied during rendering is much more noticeable than the video output filtering, I use the later one, the result is that the 352 pixels wide image is upscaled to approximately 720 pixels by the Wii video output. SInce the scaling ratio is much more important than before, the filtering is also much more noticeable.

Now, VC does not emulate the horizontal borders AND does not reproduce the exact original aspect ratio, it simply doubles the horizontal resolution, which makes the screen a little bit narrower that it should be.

Personnaly, I didn't see much differences when running the emulator in original mode with borders against a real mega drive, on the same screen and the same connection type (RGB).

[Former user]

Comment # 4 originally posted by thiagoalvesdealmeida on 2010-01-13T17:13:32.000Z:

Let me try to understand:

I know that Genesis games use 320x224 (or 256x224 with a few games), but with the added horizontal border produced by the hardware itself the final resolution will be 320x240 (in order to match a NTSC standard). I'm sorry, but I still didn't understood why the horizontal resolution is different with borders turned on or off, since it will only affect the vertical resolution.

Anyway, I think the borders itself are not really important (mainly because they will always be hidden by SDTV overscan), but the resolution is.

So, is it a fact that Wii hardware is not capable of true 320x240? In that case, VC is using 640x240 upscaled in order to replicate 320x240?

[Former user]

Comment # 5 originally posted by ekeeke31 on 2010-01-13T17:45:56.000Z:

Because there are horizontal borders as well.

There is no such things as "true" 320x240 or not, you need to understand how analog video works first:

Vertical resolution is fixed by the number of visible lines: it's 243 (non-interlaced) for the Genesis (of which only 224 are 'active' i.e where you can display your stuff, the rest being vertical borders). The Wii can either output 240 (in non-interlaced mode) or 480 'active' lines (i.e lines you can control). I use this to reproduce colored borders.

Horizontal resolution is fixed by the hardware pixel clock and the line duration: in most genesis games, there are 420 dots per lines, of which 348 are visibles , and only 320 'active' (the rest being horizontal borders). The Wii can output up to 720 active pixels (i.e pixels you can modify). Again, I used this to reproduce colored borders (horizontal).

Now, the pixel clock also determines the aspect of pixels on your TV screen: since line duration is fixed by Video standards , the less pixels you have per line (i.e the slower pixel clock you have), the more stretched they are displayed on TV screen. Since the Wii and Genesis hardware does not have the same pixel clock, I had to adjust the horizontal width and scaling so it matches what I got on my TV with a real Genesis. After some experimentation, I found out that 352 native pixels upscaled to 720 was the best match.

[Former user]

Comment # 6 originally posted by ekeeke31 on 2010-01-13T17:51:27.000Z:

Note that when I speak about "visible" pixels or lines, this is how it is defined by video standard: in reality, it depends on what your TV allows you to see. Most generally, you don't or only partially see the borders because they are hidden under TV edges or your TV just don't display every lines.

[Former user]

Comment # 7 originally posted by thiagoalvesdealmeida on 2010-01-14T01:58:02.000Z:

I didn't know there was borders on the horizontal resolution (never saw these).

OK. Wii use a higher pixel clock than Genesis (which means a slightly narrower image), but I think the difference in horizontal size is minimal enough to not worry about or notice.

So, with all due respect, I don't think that trying to get a 100% aspect ratio like a real Genesis is the best approach, since matching the correct resolution will have a much bigger impact on the quality of the picture. IMO, trying to avoid any interpolation, like VC, is better. Maybe you have a different opinion - and that's understandable. I only saying what my eyes tell me. Perhaps an option to accommodate both is the best way to go.

[Former user]

Comment # 8 originally posted by ekeeke31 on 2010-01-14T07:51:53.000Z:

Well, it's not only for the aspect ratio, it's the only way to get horizontal borders visible.

Since the internal buffer for rendering is limited to 640 pixels widely, if I want to render horizontal borders as well as active pixels (352 pixels in total), I have no other solution than using the video hardware scaling ability:

.if I simply double the width when rendering (i.e stretch to 704 pixels), borders will be outside the rendering window and not visible.

.if I stretch to 640 pixels during rendering then to 704 pixels using video hardware scaling, it will either be much more blurry (because of bilinear filtering applied by the rendering hardware) or produces scroll screen tearing (when bilinear filtering is disabled, because of the odd scaling ratio).

Now, if you set the aspect to FIT SCREEN, you can adjust the horizontal scaling and (maybe) get ride of video hardware filtering by reducing the default xscale value until you get an exact 2x scale ratio.

A solution might be to render the screen in 2 or 3 passes, first the active window (320 pixels) then the border regions, I don't know if it's feasible though. Anyway, as i said, i dont think the difference in blurryness is so much visible (compared to when bilinear filtering is ON for example) so it does not have high priority, I leave this as an open issue though for further reference.

[Former user]

Comment # 9 originally posted by ekeeke31 on 2010-01-14T07:53:41.000Z:

[Former user]

Comment # 10 originally posted by ekeeke31 on 2010-01-14T07:58:58.000Z:

For now, you can also disable the borders and get the exact same result as VC.

[Former user]

Comment # 11 originally posted by thiagoalvesdealmeida on 2010-01-15T16:10:55.000Z:

I tried the Win32 version of your emulator. Are you talking about these big horizontal borders on the picture?

http://img109.imageshack.us/i/genesisplus.jpg/

It's hard for me to believe they really should be there, mainly because your version of genesis plus is the only emulator that adds horizontal borders (not even Kega Fusion, more accurate than any other emulator, have borders on the horizontal resolution).

As you said, when these borders are on the image is wider (352x240). Consequently it will mess with Genesis intended aspect ratio (4:3 = 1,3333) and need a heavier filtering to be corrected. So, I think these horizontal borders are not needed (and why do you think they should be visible is beyond me).

Anyway, just disabling the borders will get you a picture without interpolation. So, it's a problem easy to avoid. Unfortunately I can't say the same about SMS, NES and SNES emulators.

[Former user]

Comment # 12 originally posted by ekeeke31 on 2010-01-16T00:11:29.000Z:

Believe me, they ARE here (a good example is Sonic 2 or Street Racer, on real hardware off course): most emulators does not emulate this because it's generally not "very" visible on TV screen anyway and because there is no point in emulating this on a computer screen or in a window (genplus-sdl version is a just a way for me to test the emulation core more quickly, it's not meant to be nice to look at and definitively does not output accurate aspect ratio )

Anyway, I emulate them for the sake of accuracy and because I like when the emulator output looks exactly like my old Mega Drive, running side by side on the TV screen.

And no, it does not mess Genesis intended aspect ratio because 4:3 is NOT intended to be 320x240 (remember genesis pixels are NOT square), it's more something like 320x224 (see how your TV, which screen is indeed 4:3, fill the screen with 320x224 pixels --60hz TV off course, PAL is a little different) with the exact 4:3 being 348x243 as already explained above. So, in contrary, emulating borders and scaling this way let me output a more accurate aspect ratio.

Now, I agree with you that the differences might not be worth the filtering downsides, that's why if you don't like this, you have the possibility to scale the screen exactly as you want or/and disable border emulation. You can perfectly setup a 320x240 image with black borders like any other emulators do if you want.

I leave this issue as open because I think it is maybe possible to do this with no filtering at all, by rendering the screen in more than one pass. This is however not a big priority for the moment but could be interesting to try.

[Former user]

Comment # 13 originally posted by ekeeke31 on 2010-05-25T06:50:47.000Z:

[Former user]

Comment # 14 originally posted by ekeeke31 on 2010-06-15T06:54:12.000Z:

I added separated borders option so you can turn OFF horizontal borders (making the screen output as raw as possible) while having vertical colored borders.

[Former user]

Comment # 15 originally posted by thiagoalvesdealmeida on 2010-06-16T22:18:33.000Z:

Thanks. That's exactly what I had in mind in the first place. I think this should be the default option (since it looks better), but that's up to you.

[Former user]

Comment # 16 originally posted by ekeeke31 on 2010-09-25T17:13:54.000Z:

[Former user]

Comment # 17 originally posted by ekeeke31 on 2010-12-04T17:26:03.000Z:

[Former user]

Comment # 18 originally posted by ekeeke31 on 2010-12-04T17:27:28.000Z:

[Former user]

Comment # 19 originally posted by ekeeke31 on 2011-03-09T18:46:14.000Z:

Initial idea (copying larger display to xfb in multiple passes) is impossible because of hw limitation, disabling horizontal borders is the best option you have