Add double and scanlines options for interlaced line mode

[mark_k]

Following from the recent "remove interlace artifacts" thread...

The ShowANIM animation player always forces interlace mode on, so even when playing non-interlaced animations the display is interlaced. Thus there are deinterlacing artifacts when run in WinUAE.

To work around that the user can set interlaced line mode to single, and to compensate for the now-half-height image, scale the image by 2✕ vertically. But I think two additional interlaced line mode options would be good in this case: Double and Scanlines. Both would work just like the non-interlaced equivalents.

Then both non-interlaced and interlaced line mode settings would have all the same options, with interlaced also having the legacy "double, frames".

A GUI suggestion: Make both line mode settings into drop-down boxes (as for e.g. the buffering and windowed/full-screen/full-window settings). With that type of control the user can move the mouse over the control and use the mouse wheel to adjust the setting, which doesn't work for radio buttons. That would also free up some space, possibly allowing the display-related Graphics API and DirectDraw controls to be moved from the Miscellaneous panel to the Display panel.

[DamienD]

I think this is a very good suggestion mark_k

Love scanlines so if they are available in all graphic modes then great

...but the other important thing you've raised is freeing up some space to possibly allow the display-related Graphics API and DirectDraw controls to be moved from the Miscellaneous panel --> Display panel.

I know myself that I originally missed where this was located.

[Toni Wilen]

Originally Posted by mark_k

possibly allowing the display-related Graphics API and DirectDraw controls to be moved from the Miscellaneous panel to the Display panel.

Not going to happen. DirectDraw is obsolete, it stays where it is and no new features will support it.

[Toni Wilen]

Originally Posted by mark_k

Both would work just like the non-interlaced equivalents.

Please explain. How is that going to work?

[mark_k]

For both double and scanlines, WinUAE would treat all fields the same (e.g. all as long, as for non-interlaced modes). The double display would look like single line mode with 2✕ vert. size in filter settings. The scanlines display would be similar: both odd and even fields treated as long. So lines from even field in output lines 1, 3, 5, 7... with output lines 2, 4, 6, 8... black. And same for lines from odd field.

Both settings would mainly be useful for the case where some program (animation player) forces interlace mode. Maybe some video titling software does that for video recording compatibility? [Does any software for the FireCracker-24 force interlace mode? That might be required on real hardware, when using the FC-24's 241-line mode.]

So both quite "niche" use cases, though there are quite a few of those AGAtron animation disks that all use the same player.

ED-209 mentioned a couple of demos which use "real" interlaced modes and single line mode removing fringing (at the expense of vertical resolution) here, so some people might want to use the suggested line modes even in that case.

[Toni Wilen]

I don't think it can be done without major changes.

Emulation still needs to emulate alternating fields for compatibility reasons. Those settings must not affect compatibility, only what user sees.

Line doubling feature can only double current line with previous line's data which does not look that good when line position toggles between odd and even y-coordinate.

[mark_k]

It would be kind of the opposite to the "double, fields(+)" non-interlaced line modes. With those, you effectively simulate the appearance of an interlaced display on real hardware ("double, fields" with deinterlacer, "double, fields+" without).

A double interlaced line mode (at least how I'm suggesting) would be of most use where interlace mode is forced, as with ShowANIM playing non-interlaced animations like on the AGAtron disks. In that case you can recover the corresponding 50/60fps non-interlaced output exactly. (That's what setting line mode to Single does.)

Line positions in the output would be the same for both odd and even fields. For example double interlaced line mode:

Output frame 1:
output line 1 <== odd field line 1
output line 2 <== odd field line 1
output line 3 <== odd field line 2
output line 4 <== odd field line 2
output line 5 <== odd field line 3
...
Output frame 2:
output line 1 <== even field line 1
output line 2 <== even field line 1
output line 3 <== even field line 2
output line 4 <== even field line 2
output line 5 <== even field line 3
...

The scanlines interlaced line mode would just have alternate output lines black, as for the non-interlaced case:

Output frame 1:
output line 1 <== odd field line 1
output line 2 <== black
output line 3 <== odd field line 2
output line 4 <== black
output line 5 <== odd field line 3
...

Output frame 2:
output line 1 <== even field line 1
output line 2 <== black
output line 3 <== even field line 2
output line 4 <== black
output line 5 <== even field line 3

[Toni Wilen]

Originally Posted by mark_k

Line positions in the output would be the same for both odd and even fields. For example double interlaced line mode:

No, in double mode emulation does not work that way. It works this way:

No-lace:

0 and 1
2 and 3
4 and 5

(same in both fields)

Interlace:

Field 1:

0
2
4
6

Field 2:

1
3
5
7

Interlace + double would be:

Field 1:

0 and 1
2 and 3

Field 2:

1 and 2
3 and 4

[mark_k]

That's different to the "double" interlaced line mode that I'm suggesting though?

What I'm suggesting would basically ignore whether the display is interlaced, and treat every field as odd, working like the double non-interlaced line mode then. Each output frame would contain (doubled) lines from a single field.

[If I understood what you wrote correctly, you described the current double, frames or double, fields interlaced line modes.]

BTW I found another program that can set the LACE bit in gb_system_bplcon0: Deluxe Video III. (I didn't bother figuring out how to use it, so don't know if e.g. there's a "force interlace mode" flag in each project file.)

[Toni Wilen]

Originally Posted by mark_k

That's different to the "double" interlaced line mode that I'm suggesting though?

What I'm suggesting would basically ignore whether the display is interlaced, and treat every field as odd, working like the double non-interlaced line mode then. Each output frame would contain (doubled) lines from a single field.

Which would require showing all interlace fields as odd only (or even only). I already said it is not possible in doubled mode.

[mark_k]

Originally Posted by mark_k

BTW I found another program that can set the LACE bit in gb_system_bplcon0: Deluxe Video III. (I didn't bother figuring out how to use it, so don't know if e.g. there's a "force interlace mode" flag in each project file.)

There is a per-project force interlace flag. Run DVMaker, load the "Tune" example and double-click View. There's a Force Interlace option in the requester which appears. It's checked for the Tune project, but not for any of the other examples.