[Scummvm-tracker] [ScummVM :: Bugs] #12704: Aspect ratio and resolution issues on 2.2.1 pre

[ScummVM :: Bugs]

#12704: Aspect ratio and resolution issues on 2.2.1 pre
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Reporter:  notimp  |      Owner:  (none)
    Type:  defect  |     Status:  new
Priority:  normal  |  Component:  Port: Wii
 Version:          |   Keywords:
    Game:          |
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 This is a rather complex problem to approach - but as I like the Wii
 version of ScummVM very much, I would be thrilled if it could be tested
 and fixed in future versions.

 The issue lays with analogue video modes and how they are handled on the
 Wii build.
 The Wii supports 4:3 and 16:9 video output modes both of which output an
 SD signal, that in the 16:9 case has to be stretched by the TV itself.

 For the issue description, lets stick to Wii screen settings of 4:3 and
 480p as 'the desired' output format - where ideally scaling would fall in
 line with the best possible result.

 This is how the Wii port is conceptualized currently, because if I chose
 16:9 and 480p in the Wii display menu - the current sliders in ScummVM
 (custom Wii menu) for stretching and shrinking x and y axis of the image
 dont allow to even get close to a 4:3 aspect ratio, regardless of slider
 settings, because the x axis remains too wide (stretched to 16:9 by the
 tv) - lets ignore that for now (even call it desired behavior), as most
 ScummVM games are 4:3 anyhow - so starting up ScummVM in 4:3 480p would be
 desired anyhow (less stretching).

 The issue now becomes, that its currently impossible to get aa correctly
 scaled 640x480 (so 480p) image out of the console currently.

 Tested with Broken Sword 1 and other games, but Broken Sword is a good
 testcase, as it is 640x480 natively.

 Bug description.

 When booting up Broken Sword 1, with both (Wii specific) ScummVM Menu
 sliders for image adjustment (wii_video_default_underscan_x and y) zeroed,
 you'll notice, that the output is weirdly stretched on the x axis. Even
 when aspect ratio correction is on, which is probably superseeded by the
 "wii_video_default_underscan_x and y" implementation.

 This wouldn be such an issue, if you could expand the x axis, but you cant
 (already maxed out), you so have to start to reduce image height in the y
 dimension (usually by 8 or more in the wii_video_default_underscan_y
 option), which results in not the entire 640x480 resolution being able to
 be used for the game to be displayed.

 This not only causes image degradation, but entire lines of the signal
 being discarded, which in Broken sword (native 640x480) shows up in
 distortion on dialogue text (you have to enable speech and text in ScummVM
 settings), on some dialogue lines, where the text renders missing the last
 line of pixels and looks cut off. You can also see it as line blacking
 (and cut off lines), on the looking glass symbol in the same game, when
 moved across the screen vertically.

 Its reproducible in the intro sequence of the game (first 15 minutes or
 so), so it shouldnt be hard to replicate.

 Now, here comes the proposal. While I understand the need for ovescan
 compensation (underscan) on consoles that only support analog signal out -
 the current solution, very easily - and actually by default breaks aspect
 ratio correction (at least on games where pixels are supposed to be square
 (so Broken Sword 1). The workaround that was suggested by people for three
 years now ( https://forums.scummvm.org/viewtopic.php?f=16&t=14342 ),
 namely setting wii_video_default_underscan_y to 8 or higher, cuts into the
 available vertical resolution, which in itself causes large issues with
 native 640x480 games.

 Please provide, at least one mode, where with the Wii set to 4:3 and 480p
 aspect ratio correction (ScummVM feature) gets applied correctly and the
 entire 640x480 resolution is used for image content (with no overscan
 compensation (underscan) in place).

 Most of the TVs available today are able to be set to 'just scan', where
 no overscan in image content is expected, and thereby display 640x480
 games correctly (At least in 480p output mode on the Wii). This would be
 expected behavior, and results in the highest quality output possible
 (integer scaled or native 640x480 resolution images) - currently, the
 default output is broken aspect ratio wise, and the workaround cause even
 more substantial issues (lines of pixels missing)). Leave the other mode
 in there as well, for people that actually have to apply overscan
 compensation.

 I hope that I've laid out the issue in as much detail as needed to
 understand it, and would love to see this addressed in the future.

 I also understand, that seeing the behavior isnt as easy on a 4:3 CRT (and
 all of the Wiis outputs are analog.. ;) ) but with even a decent sub 100
 USD scaler like the OSSC the described behavior (and the issues it causes
 currently) very much become obvious.
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Ticket URL: <https://bugs.scummvm.org/ticket/12704>
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