Skip to content

README.md

Latest commit

 

History

History
80 lines (62 loc) · 4.08 KB

README.md

File metadata and controls

80 lines (62 loc) · 4.08 KB
Raw

DoubleDroid — DoubleTalk PC speech synthesizer for Android

An Android text-to-speech engine that is a real RC Systems DoubleTalk PC: it runs the card's original 80C188EB firmware in the doubletalk-pc standalone emulator (vendored MAME CPU core), compiled for Android with the NDK. Select it as your system TTS engine and TalkBack — or any app that speaks — comes out of a 1993 ISA text-to-speech card, complete with Perfect Paul and friends.

Nothing here reimplements the speech algorithms: the firmware does all the synthesis, exactly as on hardware. The firmware ROM is proprietary and is not included — you import your own dump in the app (see below).

How it works

Layer What
app/src/main/cpp/doubletalk/ The emulator core, vendored from doubletalk-pc: MAME 8086/80186 + 80C188EB CPU core, compatibility shim, board wrapper, dtalk C API
app/src/main/cpp/dtalk_jni.cpp JNI bridge to the dtalk C API
DoubleTalkEngine.kt Owns the single emulator instance; serializes all native calls; builds the card's 0x01-command utterance prefixes (same WYSIWYG logic as the NVDA driver)
DoubleTalkTtsService.kt TextToSpeechService: maps Android rate/pitch/voice onto the card's nS/nP/nO commands and streams the firmware's 10,504 Hz PCM (16-bit, through the modeled output stage) to the TTS callback
SettingsActivity.kt ROM import + verification, default voice, output filter, rate boost, and the manual's voice-quality knobs (tone/articulation/expression/formant/reverb), plus a local test-speech button

The 8 firmware voices (Perfect Paul, Vader, Big Bob, Precise Pete, Ricochet, Biff, Skip, Robo Robert) are exposed as Android Voices, selectable per-request by apps or as the engine default in settings.

Android's speech-rate setting maps to the card's nS 0–9 (normal = 5S, the card default); pitch scales relative to each voice's own preset pitch so "normal pitch" always sounds like that voice. The optional rate boost rescales the firmware's rate table in RAM for faster-than-9S speech with pitch preserved, exactly as in the NVDA add-on.

Building

Requirements: Android SDK (platform 35, build-tools), NDK 27, CMake 3.22, JDK 17+. Point local.properties at your SDK, then:

./gradlew assembleDebug     # app/build/outputs/apk/debug/app-debug.apk

Installing and using

  1. Install the APK.
  2. Open DoubleDroid and tap Import ROM… to supply your 512 KB doubletalkpc.bin firmware dump. The app verifies it (CRC32 66685631, SHA-1 bf7e78d6381c76d291ee069971873347a314ffff) and boot-tests it in the emulator before accepting.
  3. Try the Speak button on the same screen.
  4. System settings → Accessibility (or Sound) → Text-to-speech output → select DoubleTalk PC (emulated) as the preferred engine.

Voice, output filter (the card's authentic 3 kHz reconstruction filter or a brighter 4.8 kHz), rate boost, and voice-quality knobs live in the same settings screen (also reachable via the gear next to the engine in system TTS settings). "Auto" on a quality knob follows the selected voice's own firmware preset.

The firmware ROM

doubletalkpc.bin (512 KB) is proprietary RC Systems firmware and carries no redistribution grant. Supply your own dump (e.g. read from a DoubleTalk PC card you own). The app stores it in its private data directory only; the repository .gitignore blocks *.bin so it cannot be committed.

Licensing

All code in this repository is BSD-3-Clause — the Android engine and the vendored doubletalk-pc / MAME sources alike. See LICENSE and app/src/main/cpp/doubletalk/NOTICE for per-component attribution. The firmware ROM is proprietary and never distributable with this software.

Credits

  • David Sexton — doubletalk-pc standalone emulator, dtalk C API, NVDA driver this engine's parameter mapping is ported from.
  • Christopher Toth — 80C188EB CPU support in the MAME core and the firmware-to-audio reverse engineering.
  • MAME and its contributors — the 8086/80186 CPU core.