Speech-to-Text — Overview

// api/assistant-api/internal/type/transformer.go
type Transformers[IN any] interface {
    // Initialize sets up the provider connection (WebSocket, gRPC, HTTP client).
    // Called once per call session before audio begins.
    Initialize() error

    // Transform sends one audio packet to the provider.
    // Transcription results are delivered via the onPacket callback registered at construction.
    Transform(ctx context.Context, in IN) error

    // Close tears down the connection and releases resources.
    Close(ctx context.Context) error
}

// Type alias for STT
type SpeechToTextTransformer = Transformers[UserAudioPacket]

// api/assistant-api/internal/transformer/transformer.go
func GetSpeechToTextTransformer(
    ctx        context.Context,
    logger     commons.Logger,
    provider   string,                     // AudioTransformer constant string
    credential *protos.VaultCredential,    // decrypted vault credential
    onPacket   func(STTPacket),            // callback invoked with each transcript result
    opts       utils.Option,               // assistant-level options (language, model, etc.)
) (SpeechToTextTransformer, error)

// api/assistant-api/internal/transformer/transformer.go
const (
    DEEPGRAM              AudioTransformer = "deepgram"
    GOOGLE_SPEECH_SERVICE AudioTransformer = "google-speech-service"
    AZURE_SPEECH_SERVICE  AudioTransformer = "azure-speech-service"
    CARTESIA              AudioTransformer = "cartesia"
    REVAI                 AudioTransformer = "revai"
    SARVAM                AudioTransformer = "sarvamai"
    ELEVENLABS            AudioTransformer = "elevenlabs"
    ASSEMBLYAI            AudioTransformer = "assemblyai"
)