STT / TTS Providers

// api/assistant-api/internal/transformer/deepgram/deepgram.go

type deepgramOption struct {
    key    string          // API key from vault credential
    logger commons.Logger
    mdlOpts utils.Option  // assistant-level options (language, model, etc.)
}

func NewDeepgramOption(
    logger          commons.Logger,
    vaultCredential *protos.VaultCredential,
    opts            utils.Option,
) *deepgramOption {
    credentials := vaultCredential.GetValue().AsMap()
    return &deepgramOption{
        key:     credentials["key"].(string),  // vault credential key
        logger:  logger,
        mdlOpts: opts,
    }
}

// api/assistant-api/internal/transformer/deepgram/stt.go

type deepgramSTT struct {
    opt      *deepgramOption
    onPacket func(STTPacket)        // callback when transcription arrives
    client   *client.WSUsingCallback
}

func (d *deepgramSTT) Initialize() error {
    // Builds LiveTranscriptionOptions from deepgramOption.SpeechToTextOptions()
    // Creates a WebSocket connection using the Deepgram SDK
    // Registers onPacket as the transcript callback
    d.client = client.NewWSUsingCallback(...)
    return d.client.Connect()
}

func (d *deepgramSTT) Transform(ctx context.Context, in UserAudioPacket) error {
    // Streams raw audio bytes to Deepgram over the WebSocket
    return d.client.Stream(bufio.NewReader(bytes.NewReader(in.Audio)))
}

func (d *deepgramSTT) Close(ctx context.Context) error {
    // Cancels context and stops the WebSocket client
    return d.client.Stop()
}

// api/assistant-api/internal/transformer/deepgram/tts.go

func (d *deepgramTTS) Initialize() error {
    // Connects to: wss://api.deepgram.com/v1/speak?encoding=linear16&sample_rate=16000&model=<voice>
    d.conn, _, err = websocket.DefaultDialer.Dial(d.opt.GetTextToSpeechConnectionString(), headers)
    // Starts goroutine to read audio chunks and call onPacket
    go d.readAudioChunks()
    return err
}

func (d *deepgramTTS) Transform(ctx context.Context, in LLMPacket) error {
    switch pkt := in.(type) {
    case InterruptionPacket:
        // Send {"type":"Clear"} to cancel queued audio
        return d.conn.WriteJSON(map[string]string{"type": "Clear"})
    case LLMResponseDeltaPacket:
        // Send {"type":"Speak","text":"..."} for each token
        return d.conn.WriteJSON(map[string]string{"type": "Speak", "text": pkt.Text})
    case LLMResponseDonePacket:
        // Send {"type":"Flush"} to trigger final synthesis
        return d.conn.WriteJSON(map[string]string{"type": "Flush"})
    }
    return nil
}