gemba

A GBA emulator frontend powered by teek and libmgba.

A full-featured GBA player with video/audio rendering, keyboard and gamepad input, save states, and a settings UI.

Installation

See INSTALL.md for platform-specific dependency setup.

Usage

gemba [command] [options]

Commands

Command	Description
play	Play a ROM (default if omitted)
record	Record video+audio to .grec (headless)
decode	Encode .grec to video via ffmpeg
replay	Replay a .gir input recording
config	Show or reset configuration
version	Show version

Run gemba <command> --help for command-specific options.

Examples

# Play a ROM (these are equivalent)
gemba game.gba
gemba play game.gba

# Play with options
gemba play --scale 2 --fullscreen game.gba

# Record 10 seconds of gameplay (headless)
gemba record --frames 600 game.gba

# Show recording stats
gemba decode --stats recording.grec

# Encode to video
gemba decode -o clip.mp4 recording.grec

# Replay an input recording
gemba replay session.gir

# Reset config
gemba config --reset

Features

• GBA emulation via libmgba
• SDL2 video rendering with configurable window scale (1x-4x)
• Integer scaling and nearest-neighbor/bilinear pixel filtering
• GBA color correction (Pokefan531 formula) for authentic LCD appearance
• Fullscreen support
• SDL2 audio with volume control and mute
• Keyboard and gamepad input with remappable controls and hotkeys
• Quick save/load and 10-slot save state picker with thumbnails
• Turbo/fast-forward mode
• ROM info viewer
• Persistent user configuration with settings UI

Language Support

The UI supports multiple languages via YAML-based locale files. The active language is auto-detected from the system environment (LANG) or can be set manually in the config.

Currently supported:

Language	Code
English	en
Japanese	ja

To force a specific language:

Gemba.user_config.locale = 'ja'

Adding a new language: create lib/gemba/locales/<code>.yml following the structure in en.yml.

Future Ideas

• Game picker / ROM browser
• GB/GBC support
• ROM patching (IPS/UPS)
• Local multiplayer (link cable emulation)
• RetroAchievements integration
• Solar sensor and tilt/gyro cartridge emulation
• Audio visualizer / channel debug view
• Ruby scripting API

Supported Platforms

Platform	Notes
macOS (Apple Silicon)	Primary development platform
Linux (x86_64)	Tested in CI via Docker (Ubuntu 24.04)
Windows 10+	Tested in CI (GitHub Actions) and manually in VM

License

MIT. See THIRD_PARTY_NOTICES for bundled font licenses.