BGB version 1.6.2

this is a gameboy/color emulator/debugger for win32 which will probably never be finished

disclaimer:

table of contents

right click menu:

default keys:

features in this version:

• emulation of the GameBoy, GameBoy Color, and Super Gameboy
• accurate emulation of the hardware, based on research with lots of test roms, useful for debugging/rom development. some highlights:
  • clock exact timing of LCD behavior/state changes
  • realistic initial ram values - random but with specific bit patterns, and simulated values left by bootroms (for example "nibbler (pd)" depends on this)
  • accurate emulation of LCD register writes during scanline (prehistorik man, demotronic demo)
  • emulation of inaccessible VRAM and OAM as on real hardware
  • 10 sprites per line limit
  • clock exact emulation of sprites causing mode 3 to take longer
  • correct memory access timing (access happening at the last/second to last clock of an opcode)
  • accurate emulation of the differences between DMG and GBC, including timing differences, differences in hardware behavior, initial state, etc.
  • can run a GBC rom as on a DMG, and a DMG rom as on a GBC
• powerful debugger:
  • disassembler
  • assembler (change code and ability to save modified rom)
  • symbols (SYM file) support
  • "inline" editing in code, data, and stack viewer
  • breakpoints
  • watchpoints (break on access)
  • conditional breakpoints
  • "on jump" watchpoints for breaking before a jump into a range is taken.
  • source code breakpoints (ld b,b)
  • singlestepping/tracing/animating/step out/step over
  • reverse singlestep, stepout, stepover (rewinding back in time)
  • vram viewer: BG map, tiles, OAM, palette.
  • IO registers viewer
  • live display of data during emulation and freezing of ram values
  • break on exceptions (accessing inaccessible VRAM, read unitialized RAM, echo ram access, access locked external ram, disable lcd outside vblank)
  • ability to modify all registers and state at any time
  • joypad window allows simulating button presses at any time while debugging
• SGB multiplayer with up to 4 gamepads
• rewind key
• graphics output: GDI, DirectDraw, Direct3D, OpenGL, null output
• graphics doubler: HQ2X, Scale2x, scanlines filter, blocky, dot matrix, GBC RGB
• sound output: waveout, directsound, Xaudio2, null, and disk writer supported. support for writing the 4 channels to separate wav files
• AVI recording, to installed system codec of choice. No sound included but is in sync and conveniently named with recorded wav file.
• runs almost all roms perfectly, compatibility comparable with the best GB/C emulators
• Accurate/high quality sound emulation, bandlimited synthesis
• accurate video emulation including "high color" graphics, correct sprite/background priorities, 10 sprites/line limit, and mid-scanline register changes.
• This emulator is fast.
• Joystick/Gamepad support, everything mappable to every button
• some user interface keys are configurable and can be mapped to joystick/gamepad buttons
• MBC3 Real Time Clock emulation. RTC is saved/loaded in the .sav file, compatible with VBA
• Auto delay/frameskip, emulation runs at 100% real speed and full 60 fps
• GameGenie and GameShark cheat, load/save cheats (auto and manual), "cheat searcher", easy creation of new cheat codes
• save/load state with quick (zsnes style, and mappable) keys, and preview screenshots for slots in select window.
• Load from ZIP and GZIP files
• good OS/platform compatibility/low requirements (works well on wine, windows 98, and on slow/old PCs)
• support for optional border bitmap or PNG file, and pseudo and real fullscreen modes.
• TCP/IP game link support

supported platforms/system requirements

BGB x86 version tested to work on windows 95b, 98 SE, NT 4, XP, Windows 7, 8.1, 10, and 11. Wine on linux and OS X. Requires DirextX 7 or later, OpenGL, and winsock 2. PNG support requires windows XP or later.

Minimum pentium 133 MHz, 16 MB RAM (windows 95b), minimum recommended pentium 200 MHz or faster, 32 MB RAM (windows 98). soundcard and joystick/gamepad are optional. A videocard with 3D hardware acceleration is recommended. BGB runs perfectly on an atom netbook.

BGB x64 version tested to work on Windows XP 64 bits, Windows 7, 10, 11, and Wine on linux and OS X.

accurate emulation and broken PD roms:

known problems:

• bgb 0.x will hang/crash when attempting to open bgb 1.0 save states because the old save state format had no version information.

SAV (battery) file format

camera emulation:

When a camera ROM is loaded, by default, the Camera Control window will show, for changing camera related settings. This can also be disabled with a checkbox in the window. The Camera Control window can also be accessed through the rightclick menu whenever a camera ROM is loaded, and through the "Other" menu otherwise. "Show preview" will show what the camera is seeing, depending on current settings. This also works if no ROM is loaded. Click "Apply" to update the preview after changing the camera source.

When the webcam is being turned on because you show the preview, or because you load a camera ROM, bgb may hang for a second up to maybe 20 seconds (seen on windows XP with an old webcam).

Development and debugging of camera ROMs: The camera's control registers and functionality are emulated accurately, based on research with a real gameboy camera, including visually close simulation of combinations of exposure, contrast, N bit, edge enhancement, edge extraction, zero voltage, and Vref. Exposure takes the real/correct time. The camera sensor's full resolution of 128x123 is emulated, of which existing camera ROMs show a 128x112 area. An image file of 128x123 or 128x112 pixels will show native without any resizing or cropping. The camera's IO registers and matrix can be seen and modified in the debugger. To do so, in the data viewer, go to 10:a000, then rightclick and "Force memory visibility".

The "Exposure" setting controls which exposure will show the image as-is. It is a hex value between 0001 and ffff. Default 800. Lower values simulate a brighter environment (as in, outdoors versus indoors) and make exposures faster.

options window:

• Sound:

  • Soundcard (auto) enable sound output to soundcard API. if this and WAV writer are disabled, sound rendering is disabled completely.
  • disable events: (off) do not time sound output on callback events. can be used with null output for performance testing.
  • 8 bits output: (off) enable this if 16 bits audio is not supported or gives problems. Gives lower sound quality, not recommended.
  • mono output: (off) enable this to output mono and mix the channels into it. useful if you listen with one headphone, or soundcard does not support stereo.
  • High quality sound rendering: (on) bandlimited synthesis. disable this if you're on a very slow PC and you're trying to speed up emulation.
  • Latency: (57) setting this higher means lower latency. setting it too high causes sound to skip.
  • WAV file writer: (off) writes WAV file. each time it is re-inited, a new WAV with a different timestamp is created
  • Save individual channels: (off) write 4 wav files for the individual hardware channels. this works in addition to/independently of "WAV file writer"
  • animation recording: (off) saves a BMP screenshot for every 1 or 2 frames (as desired), with timestamp prefix matching the WAV file and a frame number.
  • record AVI: (off) record animation to AVI. Give fourcc in box to choose codec. "Config" will open the codec's settings dialog.
  • record half framerate: (on) record ~30 fps instead of ~60 fps, saving only every other frame.
  • Samplerate: (auto) samplerate of audio to produce for soundcard or recording. "auto" detects OS mixer samplerate if available.

• Joypad:

  • click on "configure keyboard" or "configure game controller", to show the wizard. press the desired keys/buttons for the hilighted buttons.
    to change keys for user interface functions (load/save state, fast forward, reset, etc), check "configure extra buttons", then click on "configure ..."
    To change only one one or some buttons, click "skip/keep" for every other button. For each button, it says which key it is currently mapped to.
    In "configure keyboard", You can also map a button to a key combination with Ctrl / Alt / Shift.
    "configure game controller" automatically looks for both legacy (JoyGetPosEx) and Xinput API. ID 0 means not mapped/used. ID 1 to 16 are legacy API, 17 to 20 is Xinput.
  • Screenshot button: - saves, copies, both controls whether screenshot are saved as BMP or PNG file in the "scrnshot" folder, or copied to clipboard. The screenshot button can be mapped through "configure extra buttons".
  • Screenshots: bmp, png which format to use for saving screenshots or animation frames.
  • Rapid speed: control the rate of the rapid A and B buttons. the two numbers are frames pressed, and frames not pressed. Higher numbers are slower.
  • Mappable button records: button can be mapped through "configure extra buttons". Starts and stops recording.
  • Allow pressing L+R or U+D: (off) Whether to allow pressing opposite directions on the dpad simultaneously. This is not possible on real hardware, and if allowed it may glitch games.

• Misc:

  If "Save files" is empty, save files will be in the same directory as the ROM.
  • show framerate: (off) shows framerate in the window title bar, 2 numbers: drawed frames/sec, executed frames/sec.
  • freeze recent ROMs menu: (off) Use this to make "recent roms" not change. Can be used for "favorite ROMs".
  • Show errors on ROM load: (on) When loading a ROM, show if something is wrong with the ROM header so it would not work on real hardware.
  • Show warnings on ROM load: (on) When loading a ROM, show any problems/inconsistencies in a ROM header. When developing a ROM, with warnings enabled, no warnings should show.
  • reduce CPU usage: (on) causes bgb to use the minimum possible cpu by issuing sleep calls when waiting
  • reduce input latency: (auto) use an algorithm that, if vsync is used, delays input polling and emulation to reduce input-to-screen latency (Just in Time Vsync).
  • pause if losing focus: (off) pauses/stops bgb if switching to another app.
  • use fast open files dialog: (off) uses bgb's builtin open/save files dialog instead of the default windows one. The fast open dialog also allows selecting Unicode filenames.
  • framerate: (0) can be used to make bgb run slower or faster than real speed, at a desired framerate. 0 runs at the real ~59.72 fps
  • adjust sound speed: (off) change the sound's pitch to match the alternative emulation speed (like a real GB does if you change the clock signal).
  • fast forward speed: (10) how fast to run if pressing the "fast forward" button, 1 is equal to real speed. can also be used to turn the key into a "slow down" key if desired (with a value less than 1)

• Graphics:

  • frame blend: (off) various ways to mix the current and previous frames, to deal with flicker in frames or simulate LCD.
  • doubler: (off) applies a screen filter effect such as scanlines or HQ2X or LCD simulation. Multiplies output resolution (depending on filter choice) by 2, or automatic based on window size.
  • auto LCD: This choice, for frame blend and doubler, will automatically choose the LCD simulation option for DMG or GBC, and none for SGB.
  • show border: (only SGB border) choose whether to show SGB border and/or border image files around the screen.
  • SGB if set: (off) in SGB mode, as long as the game does not set a SGB border, show no border, or the border BMP/PNG image, instead of a solid black border.
  • Apply doubler to border (off) If the border is SGB, or a x1 scale image file, scale it up using the currently chosen doubler.
  • Pixel aspect ratio: (off) Lock the pixel aspect ratio of the screen to a customizeable ratio. off means aspect ratio is not locked. 1:1 is square pixels. 8:7 is like SGB. 3:2 is like GBA wide mode.
  the "auto" settings are defaults and are recommended settings. other settings may sometimes have specific benefits or uses, including troubleshooting.
  • bpp: (auto) override bits per pixel selection
  • output: (auto) override choice of output method. use GDI if other methods have problems. null can be used for speed testing (does render, but not output. to disable graphics rendering *and* outputting, change the window's height to 0 instead).
  • vsync: (auto) override choice of Vsync method. vsync eliminates tearing in the animation. one can disable vsync, or set 1 frame/vblank.
  • stretch: (blocky) instruct the graphics output to use "blocky" (point sampling) or "blurry" (bilinear filter) stretching
  • fullscreen pageflipped: (off) run in a real double/triple buffered fullscreen mode. may have benefits for performance or smooth animation
  • GBC LCD colors: (BGB 1.6) uncorrected shows raw RGB values as is. "BGB 1.6" has a more saturated/nicer blue than "BGB 1.5". "GBC reality" shows colors measured from a real GBC. Custom LUT loads a GBI compatible 32x32x32 3D LUT (BMP or PNG).
  • border image file: You can use a BMP or PNG file as border around the screen, with separate choice for DMG, SGB, and GBC emulation. Use a 160x144 pixels solid one color rectangle to define the location of the GB screen. For a x2, x3 or x4 scale border, multiply the size of the solid rectangle by the scale. You can also drag and drop a BMP or PNG file to apply it as the border for the currently emulated system.

  BGB as of version 1.6 uses GDI+, a library built into windows XP and later, to support PNG images. If GDI+ is not present, BGB still works but only supports BMP images (like older BGB versions)

• System:

  • Gameboy: runs any rom as on a DMG (original gameboy)
  • Gameboy Color: runs any rom as on a GBC (gameboy color). this also emulates a DMG ROM as on a real GBC in DMG mode, to allow testing/debugging this (for example, legend of zerd breaks as in reality).
  • Super Gameboy: runs any rom as on a SGB.
  • automatic, prefer GBC: (default) runs DMG, SGB, and GBC roms on the proper system. runs GBC+SGB roms as on a GBC.
  • automatic, prefer SGB: runs DMG, SGB, and GBC roms on the proper system. runs GBC+SGB roms as on a SGB.
  • SGB + GBC: emulates both SGB and GBC features at the same time. because this system does not exist, roms may have problems/unpredictable behavior.
  • GBC + initial SGB border: starts SGB+GBC roms in SGB mode, until they transferred a border, then resets in GBC mode. this is required for some GBC+SGB roms to show a border.
  • Gameboy or GBC: runs GBC supporting roms as on GBC, otherwise on DMG (does not enable SGB)
  • Rewind enabled: (on) allows completely disabling rewind, which can be used to reduce CPU and RAM usage or troubleshoot.
  • Rewind memory limit (MiB): (auto) limit how much RAM the rewind buffer will use at most. Currently, "auto" is max 32 MiB or 1/8th of total RAM, whichever is less. 0 is "unlimited" (max 3/4th of total RAM). 32 bits BGB caps to 1500 MiB maximum.
  • detect GB pocket / SGB2: (off) when in DMG mode, make roms detect a gameboy pocket, possibly unlocking features.
  • detect GBA: (off) when in GBC mode, make roms detect a gameboy advance, possibly unlocking features (example: "legend of zelda oracle of ages/seasons")
  • GB player: (off) if GBA mode and bootrom enabled, hard reset simulates fade and delay like a Gameboy Player
  • SGB faster as in reality: (off) if emulation is as SGB (and not as SGB2), emulate at ~61.1679 fps like a real SGB (NTSC), including sound being sharp
  • fast SGB transfers: (off) skip the initial "loading" time of a SGB rom. (This was problematic in old BGB versions but now it works well)
  • Waitloop detection: (on) detect and shortcut waitloops (which most roms use), speeding up emulation. this is done without compromise on accuracy and has no known problems so it should be left enabled.
  • boot roms: (off) run the DMG, SGB and GBC bootrom (rom images must be obtained elsewhere). If used with the "gameboy color" system setting, this lets the GBC bootrom colorize DMG roms. The bootroms are not necessary for normal emulation.

  If a bootrom is used, it will automatically be patched in ram based on "detect GBP" and "detect GBA" settings, to give accurate emulation of a GBP or SGB2 or GBA. If this behavior is undesired, find and set "BootromPatch=0" in bgb.ini.

• Exceptions:

  Controls emulation relevant for debugging roms.

  For playing games, the defaults are recommended: "Emulate as in reality", and disabling all "break on" settings. Enabling any "break on" setting will enable "debug mode" and cause emulation to use at least twice as much CPU. Except "break on invalid opcode", which has no performance penalty.

  If developing a ROM, keep "Emulate as in reality" and enable the "break on" settings to help catch common problems. If your ROM works in bgb with "Emulate as in reality" then it is likely to work on real hardware, but you should still test that too.

  To make a 3rd party unofficial ROM work which doesn't work, you can enable deliberate inaccuracies with with "Troubleshoot broken ROMs" and then enable individual inaccuracies, effectively emulating a poor emulator or a generic flash cart. This can help to pinpoint the cause of problems. Such ROMs will not work on a real gameboy, or on the real cart they report in the header. Do not rely on deliberate inaccuracies when developing a ROM.

GameGenie/GameShark cheat:

the cheat window shows a list. you can add/edit/delete cheat entries, with a code and a description. you can load/save the cheats to a file.
meaning of the letters:

• G = game genie
• S = game shark
• P = patched. means a gamegenie code changed values in the rom. if it does not show, the gamegenie code does not work for the used rom.
• E = enabled (toggled with enable/disable buttons)

In the cheat edit window, you can either enter a code, and internal values will be displayed, or you can enter internal values, and the corresponding code will be displayed.

For a gameshark cheat, you can either use "enable" to make it work constantly, or "poke" to make it change the ram value once.

Rightclick on a cheat to set a watchpoint (for gameshark codes only), or go to this cheat's ROM or RAM address in the debugger.

cheat searcher:

Play the game to the point where you want to influence behavior (for example, the game action itself) press esc to enter debugger. menu: Window -> cheat searcher. select value type (normally 8 bits) and press start.

you may be looking for a value such as "3 lives", in that case, the value in RAM may be 3 as well, but it's not guaranteed.

continue the game, walking around, killing enemies, etc, but making the value you're looking for *not* change (not dying, not getting hurt, etc), use the criteria "equal to the previous value" and search. the number of addresses displayed goes down. you can repeat this a few times. now run the game, but make the value you are looking for change, for example by dying or getting hurt in the game. now search for values which are, for example, "lower than the previous value". the number of matching addresses in the list become smaller each time you run the game and do a search, and you should end up with only one address.

Now, rightclick on the address, and choose "go here in debugger". this will select the address in the ram viewer (on the bottom of the window). then rightclick on that address, and choose "freeze ram value", and enter the desired value. This will create a gameshark code. You can open the cheat window to see the code listed.

if you want to create a gamegenie code, rightclick on the gameshark code, and choose "set watchpoint". Run the game until the value is changed (for example, die in the game), and it should stop and show the code line on which the value is changed. interpret how the code changes the value, and use game genie codes to change bytes in the code - such as changing an instruction to a nop, or change a "number to decrease" (value 01 to 00), in the cheat window, add new code, enter the address, existing and desired values, and a gamegenie code is produced automatically.

debugger hotkeys

F2	Toggle breakpoint
F3	Step Over
F4	Run to cursor
Shift+F4	Run to cursor no break
Ctrl+F4	Run to cursor reverse
Shift+F8	Step out reverse
F5	VRAM viewer
F6	Jump to cursor
Shift+F7	Trace reverse
F7	Trace (step into)
F8	Step out
Shift+F8	Step out reverse
F9	Run
Shift+F9	Run and ignore all breakpoint types
Ctrl+F9	Run and ignore the last tripped breakpoint type
F10	IO Map
F11	Options
F12	Load Rom
Ctrl+S	Save ROM as
Ctrl+L	Load state
Ctrl+W	Save state
Alt+A	Animate
Ctrl+G	Go to address
Ctrl+A	Go to PC
Ctrl+Shift+number	create bookmark
Ctrl+number	go to bookmark
Ctrl+B	go to previous bookmark or breakpoint
Ctrl+N	go to next bookmark or breakpoint
Ctrl+H	breakpoints
Ctrl+J	watchpoints
Ctrl+K	joypads
Ctrl+E	rewind cycles (or scanlines, frames, or seconds)
Ctrl+R or numpad *	reset gameboy
Right arrow	follow jump or address dereference
Left arrow	undo follow or go to address
Tab	toggle symbols view
Ctrl+Tab	go to next viewer area
Ctrl+Shift+Tab	go to previous viewer area
letter or number	Modify code/data
Ctrl+Z	Undo modify code/data
Ctrl+Alt+Z	Redo

expressions, breakpoint conditions, and debug messages

CPU registers: AF, BC, DE, HL, SP, PC, B, C, D, E, H, L, A, ZERO, ZF, Z, CARRY, CY, IME, ALLREGS
other state values: ROMBANK, XRAMBANK, SRAMBANK, WRAMBANK, VRAMBANK, TOTALCLKS, LASTCLKS, CLKS2VBLANK

These values can also be evaluated by using the menu, "Debug", "Evaluate expression".

In debug messages and expressions, VALUE is the value currently being read or written (useful when logging debug messages on watchpoints)

The unit of all "clocks" values is 1 nop in doublespeed mode, or about 0.5 microseconds. Clocks values are, like all other numerical values, in hexadecimal. The expression "ZEROCLKS" will reset the counter for LASTCLKS. TOTALCLKS is the same value as the clocks counter ("internal divider") in the IO map.

To add "ld d,d" debug messages into the code, assemble an opcode in the form: .msg 'message' where message is the message content. debug messages can contain expressions between %%. When enabled in the settings, whenever a debug message is encountered in the code, it will be logged to the debug messages window or log file.

Debug messages also support ternary operators in the form: "%boolean expression%text if true;text if false;".

The internal code that makes up a debug message is as follows: ld d,d; jr @end; dw $6464; dw $0000; db "message"; @end

One can also create debug messages that point to a null terminated text string elsewhere: ld d,d; jr @end; dw $6464; dw $0001; dw address; dw bank; @end

Commandline parameters

• [-rom] <filename of rom or state> load a rom or save state
• -setting name=value load bgb with a custom setting. this is useful for running multiple (linked) instances on a different position (with winx setting).
• -set name=value shorthand for -setting
• -listen [[addr:]port] start bgb listening for game link. if addr/port is omitted, take from settings
• -connect [addr:port] start bgb connecting for game link. if addr/port is omitted, take from settings
• -demorec filename record demo
• -demoplay filename play back demo
• -demoplayrec filename play back demo until the end, then continue recording
• -demoofs offset apply offset in bytes to demo when playing
• -demoseek offset fast forward to a point in the demo (combined with -demoplay or -demoplayrec), then presses the pause/debugger key. offset in seconds, decimals allowed, negative is "from end"
• -demonoreset disable support for $ff byte hard reset in demo
• -demo152conv filename convert demo between old (1.5.2) and new format (swap nibble order). Works in both directions.
• -demo152format play or record demos in old 1.5.2 format
• -demo157compat emulate an inaccuracy in 1.5.7 and before (only for demo playback) to allow playing old demos of some games (such as pokemon red and blue) in SGB mode.
• -headless headless mode: run without window, without sound/graphics/joypad IO. exit when it would break to debugger or when demo finishes. useful for automation. use with start /wait to wait for it to finish.
• -autoexit terminate when breaking to debugger or finishing demo playback. implied by headless.
• -nowarn suppress most warning dialogs. useful with automated or unattended use. implied by headless.
• -nowriteini do not write the bgb.ini file. implied by headless.
• -runfast run undelayed. useful with headless mode.
• -hf shorthand for -headless -runfast
• -stateonexit [filename] save a state when exiting. useful with headless mode.
• -screenonexit [filename] save a screenshot when exiting. useful with headless mode.
• -nobatt disable loading/saving of .sav (battery) files.
• -nobattsave load .sav file read only if it exists, and don't save it.
• -loadbatt filename load .sav file from filename to go with rom, regardless of -nobatt or settings. useful for automation.
• -state filename used together with -rom, you can load a save state and specify the rom to use, overriding the rom path given in the save state.
• -br [address][/[condition][/d]][/debugmsg][,...] comma separated list of breakpoints. only in combination with -rom
• -wp [address][/[value][/drwxj]][/debugmsg][,...] comma separated list of watchpoints. only in combination with -rom
• -ab alias for -wp (compatibility with older BGB)
• -watch automatically reload rom when it changes on disk
• -watchnoreset automatically reload rom, without resetting the gameboy, when it changes on disk

Demo recording/playback

The following commandline loads a rom, saves a state, and exits:

bgb -hf -br any -rom game.gb -stateonexit game.sna

bgb -rom game.sna -demorec game.dem

bgb -rom game.sna -demoplay game.dem

Demo recording of linked bgb's works, but only on the same machine, not over lan. This is done because it's the only way that both instances will run at the exact same timing, to allow the demo to be played back. To do this, also link listen or connect using commandline parameters (not the menu). Use commandlines such as the following to start the two instances:

bgb -rom red.sna -demorec red.dem -setting winx=300 -listen 127.0.0.1:8765
bgb -rom blue.sna -demorec blue.dem -setting winx=800 -connect 127.0.0.1:8765

Note: i changed the nibble order around from what it was in 1.5.2, to make it conform to the standard used everywhere: the d-pad should be in the high bits, the other buttons in the low bits. To change existing demo files between the new and old format, use the following command:

bgb -demo152conv filename.dem

How to make bgb run faster if you have a slow computer

• disable high quality sound rendering, set the sound samplerate to 22KHz, or turn sound off.
• make sure "debug mode" is not active (menu, "other", "debug mode")
• disable "mix current and last frame" and set "doubler" to "off"
• Set the desktop resolution to 16 bpp, set emulation to 16 or 8 bpp
• try "fullscreen pageflipped" mode, especially combined with 8 bpp.

full screen mode:

real (pageflipped) fullscreen modes are also available in the graphics tab of the settings.

game link:

As of 1.5.2, link in most games should work, and pokemon should work without any glitches (before, pokemon had occasional glitches). one can link between different games, for example pokemon red and blue. Also, a new feature was added: automatic connecting/reconnecting and re-listening: if the link is broken, it will connect or listen again. Also, it will keep trying to connect until it succeeded. This makes the link feature easier to use, and potentially enables unattended use. If the behavior causes problems, it can be disabled in the ini with "LinkAutoListen" and "LinkAutoConnect".

AVI recorder

I recommend getting and installing the "camstudio lossless codec". I tested version 1.5. then in bgb, set the codec field to "cscd" to choose the codec. click "Config" to open the configure dialog, and choose "gzip compression" (this will produce smaller AVI files still). Turn off "record half framerate" to record full ~60 fps, which will still not produce too big AVI files, if desired.

The codec can be uploaded as is to youtube, which supports it, or be edited and transcoded to another codec afterwards.

To stitch together multiple recordings (for example if interrupted by the debugger), it is recommended to first combine the video pieces, and the audio pieces, and then mux the audio and video together.

Note for speedrun or "race" use

bgb will, by default, run at the real speed (~59.727 fps). When using bgb for speedruns, and one is not sure whether the settings are default, make sure of the following settings, to ensure running at the real speed:

• on the "Graphics" tab, "vsync" is set to "auto" (the default), or to "Vsync disabled"
• on the "Misc" tab, "framerate" is set to "0" (the default)

• speed is locked to real speed ~59.727 fps, or optionally ~61.1679 fps for SGB only
• caption shows "bgb" + version + "SR"
• caption shows platform being emulated: "D" for DMG, "M" for GB pocket, "S" for SGB at ~59.727 fps, "SF" for SGB at ~61.1679 fps, "S2" for SGB2, "C" for GBC, "A" for GBA, "P" for GB player
• caption shows "B" if bootrom was enabled on last reset.
• messages and information are also shown as an overlay in the screen (can be disabled with "TextOverlay" setting)
• after a rom is loaded, choice of platform, GBA mode, GB player, bootrom setting, and SGB speed can't be changed (restart BGB, then change)
• if bootrom is incorrect, or failed to load when bootrom setting is enabled, show "BOOTERR" message
• rom md5 hash is shown briefly when rom is loaded or reset
• fast forward button is disabled
• rapid A/B buttons are disabled
• rewind is disabled
• message is shown in caption for reset
• caption shows "demo" if demo is being played
• on loading a state, "L" + a counter is shown in caption
• gamegenie and gameshark cheats are disabled
• debugger is locked out
• deliberately inaccurate emulation features are locked out
• invalid opcode hangs cpu as in reality
• in GBA mode and GB player setting and bootroms enabled, reset does a fade and delay like a GB player, where controls briefly still work.
• pressing L+R and U+D simultaneously setting is disabled
• recovery save state is disabled

• confirmed on GBC and GBA for: red, blue, yellow, gold, silver, crystal (english), and crystal (japanese).
• confirmed on DMG for red.
• confirmed on SGB for red and blue. (as of 1.5.8)

As of 1.5.8, hard resets (pressing the reset key, * by default), will be recorded and played back in demos. A demo can be recorded during a speedrun, and played back later in non-speedrun mode, as long as all platform settings are the same (choice of platform, GBA, GB player, bootroms), and the BGB version is the same.