Architecture

This page shows how the ZirekHQ speech components relate to each other, as a C4 System Context diagram. Each component’s own docs break its internals down further (Container, Component, and a Code-level diagram) — see dengjen-tts, dengjen-nvda, dengjen-piper-rs, and dengjen-tashkeel.

C4Context
    Person(user, "Screen reader user")

    System_Boundary(zirekhq, "ZirekHQ") {
        System(nvda_addon, "dengjen-nvda", "NVDA add-on (Python). Loaded in-process by NVDA as a synth driver.")
        System(tts, "dengjen-tts", "Rust neural TTS inference engine. Exposes CLI, C ABI, Python, and gRPC frontends.")
        System(tashkeel, "dengjen-tashkeel", "Arabic diacritization (tashkeel/harakat). Rust core with C ABI, Python, and Java bindings.")
        System(piper_rs, "dengjen-piper-rs", "Standalone Piper-format TTS inference crate. Not currently consumed by any other ZirekHQ component.")
    }

    System_Ext(nvda, "NVDA", "Open-source Windows screen reader")
    System_Ext(voices, "Voice model catalogue", "Piper / Kokoro / MeloTTS ONNX voices, e.g. huggingface.co/rhasspy/piper-voices")

    Rel(user, nvda, "Uses")
    Rel(nvda, nvda_addon, "Loads as a synthesizer driver")
    Rel(nvda_addon, tts, "Synthesizes speech via gRPC, talking to a vendored dengjen-tts-grpc binary")
    Rel(tts, tashkeel, "Optionally phonemizes Arabic input text (feature-gated, opt-in)")
    Rel(nvda_addon, voices, "Downloads voices")
    Rel(tts, voices, "Loads ONNX voice models")
    Rel(piper_rs, voices, "Loads Piper ONNX voices")

Two things worth calling out that aren’t obvious from the individual repos:

  • dengjen-nvda never talks to dengjen-tts as a library. It launches a separately vendored dengjen-tts-grpc binary as its own OS process and speaks to it over gRPC — the two are only coupled at the process boundary, not the API boundary.

  • dengjen-piper-rs and dengjen-tashkeel are not wired into dengjen-tts’s default build. dengjen-tashkeel is an optional, feature-gated dependency of one of dengjen-tts’s model crates; dengjen-piper-rs is a fully separate, parallel implementation with no dependency relationship to dengjen-tts in either direction.

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