sdk/fidl/fuchsia.speech/speech_to_text.fidl

// Copyright 2017 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

library fuchsia.speech;

[Discoverable]
protocol SpeechToText {
    /// Starts capturing speech from the microphone.
    BeginCapture(TranscriptionListener transcription_listener);

    /// Begins hotword detection. Detected hotword utterances are reported on the
    /// given listener.
    ListenForHotword(HotwordListener hotword_listener);
};

/// Represents an active transcription session. Either side may close this
/// interface to indicate that transcription should stop. If the transcription is
/// unexpectedly closed before `OnReady` is called, the implementer should treat
/// it as an error (in such cases, `OnError` is called).
protocol TranscriptionListener {
    /// Indicates that capture has begun. Prior to this, parts of the system may
    /// not have been initialized and audio may have been dropped. No calls to
    /// `OnTranscriptUpdate` will occur before `OnReady` is called.
    OnReady();

    /// Receives updated transcripts. Each call receives the most likely
    /// transcription of the entire utterance at that time. Previously transcribed
    /// text may mutate in response to later input.
    OnTranscriptUpdate(string spoken_text);

    /// Provides periodic updates on the user's speech signal power, when the
    /// microphone is open and streaming to the backend.
    /// `speech_level` is instantaneous speech power, in decibels (negative).
    OnSpeechLevelUpdate(float32 speech_level);

    /// An error occurred before or during transcription. Depending on the nature
    /// of the error, this may occur before `OnReady` is called, and `OnReady` may
    /// never be called. This binding will be closed immediately after sending this
    /// message.
    OnError();
};

/// Listens for hotwords. Each detected hotword utterance triggers `OnHotword`.
/// Closure of this handle by the speech service indicates an error.
protocol HotwordListener {
    /// Indicates that capture has begun. Prior to this, parts of the system may
    /// not have been initialized and audio may have been dropped. No calls to
    /// `OnHotword` will occur before `OnReady` is called.
    OnReady();

    /// Called for each detected hotword utterance.
    OnHotword();
};