LocalTTS iPhone Server

LocalTTS is an iOS SwiftUI app that exposes a localhost Vietnamese TTS API on the iPhone. It mirrors the public voice/model catalog used by NGHI-TTS and caches Piper ONNX model files inside the app sandbox.

Current implementation

• Runs a local HTTP server on 127.0.0.1:17771.
• Fetches Vietnamese voice names from https://nghitts.app/api/piper/vi/models.
• Caches the voice list locally.
• Prefetches {voice}.onnx and {voice}.onnx.json from NGHI-TTS.
• Defines the native Piper engine boundary for ONNX Runtime/eSpeak integration.

The API and cache layers are implemented. The final synthesis engine currently returns 501 engine_unavailable until ONNX Runtime Mobile and an eSpeak phonemizer binding are linked in Xcode.

API

GET /health
GET /v1/voices
POST /v1/models/prefetch
POST /v1/tts

POST /v1/models/prefetch

{
  "voices": ["Ngọc Huyền (mới)"]
}

POST /v1/tts

{
  "text": "Xin chào, đây là thử giọng tiếng Việt.",
  "voice": "Ngọc Huyền (mới)",
  "speed": 1.0
}

Open in Xcode

Open LocalTTS.xcodeproj on macOS, select a personal development team, then run the LocalTTS target on an iPhone. Keep the app in the foreground while another app calls http://127.0.0.1:17771.

GitHub Actions IPA builds

The workflow at .github/workflows/build-ipa.yml builds an unsigned IPA artifact on every push to main and through manual workflow_dispatch.

The unsigned IPA is useful as a CI artifact, but it is not enough for normal iPhone installation. To produce a signed IPA, add these repository secrets:

• BUILD_CERTIFICATE_BASE64: base64-encoded .p12 signing certificate.
• P12_PASSWORD: password for the .p12.
• BUILD_PROVISION_PROFILE_BASE64: base64-encoded .mobileprovision.
• KEYCHAIN_PASSWORD: temporary CI keychain password.
• EXPORT_OPTIONS_PLIST: base64-encoded ExportOptions.plist.

When all signing secrets are present, the signed-ipa job exports and uploads a signed IPA artifact.

Native Piper work remaining

To make /v1/tts produce real NGHI-TTS audio, link:

• ONNX Runtime Mobile or ONNX Runtime iOS.
• A Vietnamese eSpeak phonemizer compatible with Piper config files.
• A Swift wrapper that implements PiperEngine.

The integration point is LocalTTS/Services/PiperTTSService.swift.