[Q] Setting video mode with Falcon compatible resolution

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Patrice Mandin
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[Q] Setting video mode with Falcon compatible resolution

Postby Patrice Mandin » Tue Oct 17, 2017 8:18 pm

Hello,

A while ago, I added new extended video modes for Supervidel in SDL. However it seems it's not totally correct, so I need to know how to fix it. Currently, 0x4000 is used for all modes, but it appears it's not needed for modes that are 640x480 or less (i.e. 640x240, 320x480 and 320x240). So should I remove it? Currently, the video mode code list is this one (I don't list resolutions 800x600 or higher):

Code: Select all

   {0x403D,640,480,32,0}, /* 32 bits modes */
   {0x413D,640,240,32,0},
   {0x4035,320,480,32,0},
   {0x4135,320,240,32,0},

   {0x403C,640,480,16,0}, /* 16 bits modes */
   {0x413C,640,240,16,0},
   {0x4034,320,480,16,0},
   {0x4134,320,240,16,0},   

   {0x403F,640,480,8,0}, /* 8 bits chunky modes */
   {0x411F,640,240,8,0},
   {0x4017,320,480,8,0},
   {0x4137,320,240,8,0}

I expect the extension flag should be needed for 32 bits mode.
Falcon support 16 bits mode, so maybe it's also not needed there?

So is this list correct for all these listed modes?
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Re: [Q] Setting video mode with Falcon compatible resolution

Postby viking272 » Fri Jan 12, 2018 9:45 am

Hi Patrice, did you resolve this in the end?

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Re: [Q] Setting video mode with Falcon compatible resolution

Postby shoggoth » Fri Jan 12, 2018 3:22 pm

The extension flag is needed for resolutions which are "non-typical" for the VIDEL, e.g. 32bpp modes, or modes which takes up a lot of video RAM.

Apart from enabling these resolutions, it also changes which hardware registers that are used to set the screen address/mode, and where the actual frame buffer is located (in STRAM/snoop or SuperVidel VRAM).

There is a single exception though - and that is a "hybrid" VIDEL mode, which allows for an 8bpp chunky mode using the "normal" VIDEL registers. The idea is that this makes it easy for people to accelerate existing code (skip C2P) without knowing the ins and outs of the SuperVidel.

Feel free to contact me for some nice cooperation. After all, I steal code from you all the time :-P :)
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Re: [Q] Setting video mode with Falcon compatible resolution

Postby mikro » Sat Jan 13, 2018 12:17 am

Thanks Peter for your input! Actually it was me who started making accusations of Patrice's SDL :-P. We have been testing some video setups on my SuperVidel and I was getting just blank screens without anything, we couldn't figure out what's wrong for weeks.

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Re: [Q] Setting video mode with Falcon compatible resolution

Postby Patrice Mandin » Sat Jan 13, 2018 7:38 pm

@shoggoth: so should I correct the video mode list as this?

Code: Select all

   {0x403D,640,480,32,0}, /* 32 bits modes */
   {0x413D,640,240,32,0},
   {0x4035,320,480,32,0},
   {0x4135,320,240,32,0},

   {0x003C,640,480,16,0}, /* 16 bits modes , removing 0x4000 for all, keeping standard falcon values */
   {0x013C,640,240,16,0}, /* and keeping 0x4000 for all resolutions above 640x480 */
   {0x0034,320,480,16,0},
   {0x0134,320,240,16,0},   

   {0x403F,640,480,8,0}, /* 8 bits chunky modes */
   {0x411F,640,240,8,0},
   {0x4017,320,480,8,0},
   {0x4137,320,240,8,0}
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Re: [Q] Setting video mode with Falcon compatible resolution

Postby mikro » Sat Jan 13, 2018 11:03 pm

I think the chunky modes should be without the bit set as well.

By the way, while are you at it, why not add the extended video resolutions as well? I documented it a while ago here: https://github.com/freemint/mintlib/blo ... con.h#L173

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Re: [Q] Setting video mode with Falcon compatible resolution

Postby Patrice Mandin » Sun Jan 14, 2018 3:54 pm

@mikro: extended resolutions are already listed. I just put there the falcon compatible resolutions, which are the ones that hang when they are used.
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