Detect NTSC or PAL

[highpuff]

Hi!

I've been following this section with joy and for a few years ago I decided to re-boot my coding on Amiga. After some routines and effect made in assembler I found that the init-code that I was using was *erhm*, well, not that system friendly.

I started to write a brand new init-code and so far so good. Since I have a Indivision AGA MK1 I use two different modes. NTSC for Workbench and PAL for games/demos. It might be a better way but since the Indivison only supports either PAL, NTSC or HighGFX I had to used one for each "mode".

One part of the init-code should contain a routine that detects the original screen mode and saves it when a "Indivision" flag is defined in the top of the code.

This was harder than I though. No matter what I do, I get PAL??!

I made a quick routine where I test different to detect the screen and it looks like the code below.

When it is executed D0 returns with the value $00320032 (50 50) and gd_DisplayFlags sets D1 to $00000014 (picture CRSnap007.png).

; *******************************************
;	$VER: LibraryTest.s  0.1 (09.03.15)
;	AUTHOR: Highpuff iKod.se
; *******************************************

		incdir	"include:old/"
		;include "dos/dos_lib.i"
		include	"exec/exec_lib.i"
		include "graphics/graphics_lib.i"

		;include	"dos/dosextens.i"
		include	"exec/execbase.i"
		include	"graphics/gfxbase.i"


; *********************************************
;		Main Code AREA
; *********************************************

		Section MainCode,code

MainCode:	movem.l	d0-a6,-(sp)

		move.l	$4.w,a6
		move.l	a6,Execbase

		lea.l	GfxName,a1
		moveq	#39,d0
		jsr	_LVOOpenLibrary(a6)
		beq	.Error
		move.l	d0,Gfxbase
		
		lea.l	DosName,a1
		moveq	#39,d0
		jsr	_LVOOpenLibrary(a6)
		beq	.Error
		move.l	d0,Dosbase

		clr.l	d0
		clr.l	d1

		move.l	Execbase,a6
		move.b	PowerSupplyFrequency(a6),d0
		swap	d0
		move.b	VBlankFrequency(a6),d0

		move.l	Gfxbase,a6
		move.w	gb_DisplayFlags(a6),d1
		
		move.l	Gfxbase,d0
		beq	.noGfxLib
		move.l	d0,a1
		jsr	_LVOCloseLibrary(a6)
.noGfxLib:
		move.l	Dosbase,d0
		beq	.noDosLib
		move.l	d0,a1
		jsr	_LVOCloseLibrary(a6)
.noDosLib:

.Error:		movem.l	(sp)+,d0-a6
		rts
		
; *********************************************
;		Data AREA
; *********************************************

		Section	MainData,data

MainData:
		dc.b	"$VER: LibraryTest.s 0.1 (09.03.15)",0
GfxName:	dc.b	"graphics.library",0
DosName:	dc.b	"dos.library",0

		cnop	0,4

Execbase:	dc.l	0
Gfxbase:	dc.l	0
Dosbase:	dc.l	0

		end

My Amiga has the following specification:

• Amiga 4000 Desktop
• Phase 5 Cyberstorm PPC 060/50Mhz 128MB RAM
• Phase 5 Cybervision
• Indivison AGA MK1
• 60GB SSD to SCSI via ACard 7730A

Pictures of the screen config:

[Blueberry]

If the purpose is just to restore the original screenmode when your demo exits, the "proper" way of doing it is like this:

- Save the gb_ActiView field in GraphicsBase. This points to the current View, as managed by graphics.library.
- Call LoadView(0). This tells graphics.library to reset the view to default (PAL or NTSC, you can't rely on which).
- move.w #$0020,$dff1dc to force display to PAL.
- Call WaitTOF twice (makes sure any remaining odd/even field copperlists have completed).
- Bang the hardware as you like
- When done, call LoadView with the original (saved) view. This restores the original screenmode.

This procedure works from any screenmode, including RTG modes.

Getting all parts of the init code to fit together properly in the right order can be a bit tricky. Take a look at my init code, as discussed here: http://ada.untergrund.net/?p=boardthread&id=444 - it closes and restores the system robustly, sets op a vblank interrupt, and a few other useful things. Use it as is or just for inspiration.

[highpuff]

@Blueberry:

So if I save the gb_Actiview + gb_copinit and do all the rest all by the book and later in my code bang hardware $dff1dc with #$0020 and force my view to PAL, will the system be restore the saved gb_Actiview or do I need to set $dff1dc to #$0000 as well?

Or.. What the heck! I will try tonight (Suddenly the meeting I currently attend got very booring and I wish I was home).

Thanks so far

[highpuff]

@Blueberry:
I tried it now and if I do as you told me, like the list below.

- Save the gb_ActiView + gb_copinit fields in GraphicsBase. This points to the current View, as managed by graphics.library.
- Call LoadView(0). This tells graphics.library to reset the view to default (PAL or NTSC, you can't rely on which).
- move.w #$0020,$dff1dc to force display to PAL.
- Call WaitTOF twice (makes sure any remaining odd/even field copperlists have completed).
- Bang the hardware as you like
- When done, call LoadView with the original (saved) view. This restores the original screenmode.

If I then put #$20 in $dff1dc in my copperlist and then exit the system, it does not restore $dff1dc to $0. It seems like this register is not set either in gb_ActiView and gb_copinit.

[Leffmann]

Call RemakeDisplay before putting gb_copinit back in (read gb_copinit AFTER RemakeDisplay). Settings related to the display generator, such as vertical and horizontal frequencies, are global for the entire screen and are kept out of the Copper program inside the View.

If you want to force PAL, then it might be a better idea to check if you're on ECS and Kickstart 2.0 or higher, and just call OpenScreen with PAL_MONITOR_ID and get a blank screen without title-bar, bitmap etc. before hitting the hardware. This way you can let the system deal with all the stuff related to the display generator, which is probably a safer bet.

BTW, The display mode you get when calling LoadView(NULL) is the one you booted into, so if you f.ex. have a PAL machine and select NTSC via the early startup menu, and run 31kHz VGA in Workbench, then calling LoadView(NULL) will give you the NTSC.

[highpuff]

I might have done something wrong now, but so far it did not work. This is the schema.

- Call _LVORemakeDisplay
- Read&Store gb_copinit

- yada yada

- Call _LVORemakeDisplay
- Read&Restore gb_copinit

Still the same, I need to set $dff1dc to $0 else I do get a PAL-screen in Workbench.

I will try some more tonight and during the weekend. Thanks so far!

[Leffmann]

Try this:

LoadView(NULL)
WaitTOF()
WaitTOF()
...
Restore interrupt and DMA settings
RemakeDisplay()
cop1lc = GfxBase->copinit

It works fine in WinUAE and on my A1200, and restores from PAL or NTSC back to PAL, NTSC, VGA etc. correctly, though I don't have an Indivision to test with.

[highpuff]

Tried it in asmOne with latest includes and older ones. I cannot say that it does not work, but it also hangs the system on exit.

It does go back to NTSC so now I need to see what it is that causes the hang.

[hooverphonique]

did you forget a Permit() call before exit? or restore of intena?

[highpuff]

No, they are there and it is working with I remove the call to IntuitionBase/RemakeDisplay.

The exit does this:

1) Restore old DMA
2) Restore old INT
3) Restore old REQ
4) Exec/Permit

5) Intuition/RemakeDisplay

6) gb_inicop->$dff080
7) Kickstart CopJmp
8) Close IntuitionLib
9) Close GraphicsLib

Since this is only because I use Indivision MK1 with two separate displaymodes between games/demos and Workbench I think I will stay with my manual routine.

But it would be nice to have a routine that detects the screen mode that was before execution of the code and then be able to restore it. Else.. Cheap solution, buy a LCD that supports 15,6KHz Horizontal ( Thanks Hewitson for the reminder )

[Hewitson]

Originally Posted by highpuff

Cheap solution, buy a LCD that supports 15,6KHz vertical

Horizontal

[highpuff]

Originally Posted by Hewitson

Horizontal

Damn it... Fixed!

[Leffmann]

Does the small test program I posted above crash too? Could you post your code?

[mark_k]

Originally Posted by highpuff

But it would be nice to have a routine that detects the screen mode that was before execution of the code and then be able to restore it.

I can't help thinking there must be a way to do that. But I don't know it. There doesn't seem to be a system_beamcon0 value in GfxBase for instance.

What you could do on exiting, is force the system to write to BEAMCON0 itself. If you load an NTSC View, then load a PAL View, then restore the original View, the system should write to BEAMCON0.

[highpuff]

@Leffman: (or should I call you Master from now?)

I tried the C-application that you shared in this thread and it worked in Workbench. It seems that I made a huge bo-bo. Above the pointer to the Intuition library I had a dc.w, that SHOULD have been a dc.l, meaning that the I pointer was overwritten in a early phase.

My bad The break I had from coding on Amiga for a "few" years seem to have certain negative effects. Like my vision etc :P

Thanks again!