Pocket Heaven

Palom Junior · Member Joined: 21 Sep 2009 Posts: 9

A while back, Dwedit made mention of a PocketNES DS, and I remember something about it looking the same as the GBA version, with the screen being squished to 160 pixels tall. I had a few suggestions for this thing. That is, assuming it gets worked on.

1. Don't cut the 8 pixels on the left and right sides. After jEnesisDS, the extra few pixels will be appreciated, especially for Castlevania. "CORE" and "LAYER", ugh.

2. Like Lameboy, allow the option of placing the game area at the top of one of the screens, at the bottom, or in the middle.

3. Why not allow a bit of customization? Like a Nintendo logo, or 8-bit sprites? A 256x32 bitmap or two 256x16 bitmaps to cover the unused areas at the top and/or bottom of the screen, similar to the Super Gameboy borders.

Well, it's just a thought.

Dwedit · Posted: Tue Sep 22, 2009 12:31 am Post subject:

Many NES games will cut off the left 8 pixels, whether you like it or not. It's a hardware feature of the NES. PocketNES doesn't emulate it right now, it just cuts of everything anyway.

Hiding the 8 pixels on each side can hide lots of unsightly scrolling glitches, especially in games like Super Mario 3.

Right now, I'm rewriting the sound engine for PocketNES on the GBA.
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Palom Junior · Member Joined: 21 Sep 2009 Posts: 9

The left and right sides never bothered me before, but you're the programmer.

Asaki · Member Joined: 15 Apr 2009 Posts: 82

On analogue TVs, a small portion of the border is meant to be hidden in the overscan anyway, Castlevania being a slip-up.

Streets of Rage for Genesis slips up too, has some text a little too close to the top of the screen.

Covarr · Member Joined: 07 Jan 2006 Posts: 736

tepples · Posted: Wed Sep 23, 2009 4:29 am Post subject:

The NTSC NES pixel aspect ratio (PAR) is 8:7. Here's why:

BT.601 specifies that a pixel clock rate of 135/11 MHz = 12.273 MHz gives square pixels in an NTSC signal at 640x480i. In the hacked "240p" mode that the NES and Super NES use, halve this to 135/11 MHz = 6.1364 MHz for 320x240 square pixels.
NTSC specifies a color subcarrier at 315/88 MHz = 3.5795 MHz.
The NES master clock runs at six times the subcarrier rate. For NTSC, this is 945/44 MHz = 21.477 MHz.
The NTSC NES PPU outputs a pixel every four master clock cycles, or 945/176 MHz = 5.3693 MHz.
135/22 MHz (square pixel rate) divided by 945/176 MHz (NTSC NES/SNES pixel rate) = 8/7 PAR.

The menu of nesDS represents PAR as a scale factor, the bottom of a fraction whose top is 65536. So a setting of E000 in nesDS gives an accurate PAR: 0xE000 = 57344, and 65536/57344 = 8/7. At that size, 256x192 device pixels can represent 256x219 NES pixels, which comes close to the 256x224px visible image estimate used by popular PC-based emulators.

(For comparison, PocketNES had a PAR of 4:3, and my α-Lerp demo had a PAR of 6:5.)
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Covarr · Member Joined: 07 Jan 2006 Posts: 736

So pixels would be cut. However, the shape of the image would be just about correct when displayed on a DS.
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DKnight2066 · Posted: Sat Sep 26, 2009 1:47 pm Post subject:

Covarr · Member Joined: 07 Jan 2006 Posts: 736

Dwedit · Posted: Sat Sep 26, 2009 3:25 pm Post subject:

Still using the GBC hardware. Just making better use of it. Probably won't work well in emulators, just on hardware.
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