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Start fleshing out the "console-specific notes" section.
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Tim Allen
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docs/notes.md
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docs/notes.md
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@ -1,15 +1,137 @@
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TODO
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The consoles that higan emulates
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are similar in many ways,
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but some of them do have particular quirks
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that you should be aware of.
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The WonderSwan rotates!
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Video Shaders and the Super Famicom (and Mega Drive)
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----------------------------------------------------
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Shaders look weird on Super Famicom because of interlace/hi-res
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[Video Shaders](guides/shaders.md)
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customize how higan scales
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the low-resolution video of the emulated console
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up to the high-resolution of the computer display.
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Simple shaders
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(like "None"
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and the third-party "AANN" shader)
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just blindly scale up the images they're given,
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but sophisticated shaders
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(such as the third-party "xBR" shader)
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try to produce higher-quality output
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by recognising particular patterns of pixel,
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like taking three diagonal pixels
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and turning that into a smooth diagonal line.
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These shaders assume that
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each pixel drawn by the game's artists
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is a single pixel in the video output they analyze.
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Most of the consoles higan emulates
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can only output video at one specific resolution,
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so this "one pixel equals one pixel" rule holds true,
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and shaders like "xBR" work just fine.
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Unfortunately,
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this is not the case for the Super Famicom.
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The "normal" video mode for the Super Famicom
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draws 256 pixels across the width of the screen,
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but it also supports a "hi-res" mode
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that draws 512 pixels on each line.
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Since Super Famicom games can enable hi-res mode at any time,
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even halfway through a frame,
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higan always renders Super Famicom video output at 512 pixels wide,
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just in case hi-res mode is enabled later on.
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This means that in "normal" mode,
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each pixel drawn by the game's artists
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becomes two pixels in the video output,
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breaking the assumption pattern-based shaders are based on.
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The Super Famicom has a similar issue in the vertical direction:
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normally,
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an NTSC-based Super Famicom draws 238 rows of output,
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~60 times per second.
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This is sometimes referred to as "240p" video.
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When a game turns on "interlaced" mode,
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it draws ~480 lines of output,
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~30 times a second;
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first the ~240 odd-numbered lines,
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then going back to the top and drawing the ~240 even-numbered lines.
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This is sometimes referred to as "480i" video.
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TODO: https://board.byuu.org/viewtopic.php?p=44758#p44758
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Music and Sound Effect Volume on the Mega Drive
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-----------------------------------------------
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The Mega Drive has two different audio-generating chips:
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- the SN76489 or "PSG" chip,
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inherited from the Master System,
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mostly used for sound-effects
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like Sonic picking up rings
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- the YM2612 or "FM" chip,
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mostly used for music
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With two different sound sources,
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it's important that they have similar volumes,
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or the sound-effects will drown out the music,
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or vice-versa.
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Sega did *not* do this,
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and different hardware revisions
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used different relative volumes.
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higan currently
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sets the PSG volume to [125% of the FM volume][vol],
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based on [a Sega Genesis model 1 VA6][va6] that byuu owns.
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If you feel sound-effects in higan's Mega Drive core
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are too loud or too quiet,
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you may be comparing it
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to a Mega Drive calibrated to a different scale
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(or to an emulator tweaked to match such a Mega Drive).
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[vol]: https://board.byuu.org/viewtopic.php?p=42482#p42482
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[va6]: https://board.byuu.org/viewtopic.php?p=42195#p42195
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Playing Game Boy Colour games in Game Boy mode
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----------------------------------------------
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GBA in-game saves are Difficult
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Games for the original Game Boy
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came in solid grey cartridges,
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and only supported four-shade greyscale graphics.
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ROM files for these games
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typically have filenames ending in `*.gb`.
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PSG volume for the Mega Drive
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(see https://board.byuu.org/viewtopic.php?p=42158#p42158 for info)
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The Game Boy Color played all the original Game Boy games,
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but extended the hardware to support colour graphics.
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Games that required
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the extra hardware in the Game Boy Color
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came in transparent cartridges.
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ROM files for these games
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typically have filenames ending in `*.gbc`.
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TODO: Rename files before import!
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Or afterward.
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In-Game Saves and the Game Boy Advance
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--------------------------------------
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TODO: GBA in-game saves are Difficult
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Rumble compatibility for Game Boy (Color)
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-----------------------------------------
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TODO: Test Pokémon Pinball
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Rumble compatibility for Game Boy Advance
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-----------------------------------------
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TODO:
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Some GBA carts contained an actual rumble feature (which?),
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some only supported rumble via the GBA Player (which?).
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Which does higan support?
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WonderSwan rotation
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-------------------
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TODO: The WonderSwan rotates!
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Rumble for GB and GBA?
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