BaseTTSProvider

Defined in: src/providers/base/BaseTTSProvider.ts:73

Abstract base class shared by every TTS provider in CompositeVoice.

Remarks

BaseTTSProvider sits between BaseProvider and the two transport- specific bases (LiveTTSProvider and RestTTSProvider). It adds the audio callback and metadata callback mechanisms that all TTS providers use to deliver synthesized audio back to the SDK core, along with handler methods and guard methods for the orchestrator.

The handler/guard pattern:

1. Handler methods (processChunk, finalize) receive text data and trigger synthesis.
2. Guard methods (isAudioReady) assert conditions on audio chunks and return boolean.
3. Callbacks (onAudio / emitAudio / onMetadata / emitMetadata) deliver synthesized audio to the orchestrator.

Inheritance hierarchy:

BaseProvider
 +-- BaseTTSProvider          <-- you are here
      +-- LiveTTSProvider     (WebSocket streaming TTS)
      +-- RestTTSProvider     (REST batch TTS)

You typically do not extend BaseTTSProvider directly. Instead, extend LiveTTSProvider for WebSocket/streaming providers or RestTTSProvider for batch/REST providers.

Example

import { BaseTTSProvider } from 'composite-voice';
import type { TTSProviderConfig } from 'composite-voice';
import type { AudioChunk } from 'composite-voice';

class CustomTTSProvider extends BaseTTSProvider {
  constructor(config: TTSProviderConfig) {
    super('rest', config);
  }

  protected async onInitialize(): Promise<void> { }
  protected async onDispose(): Promise<void> { }

  processChunk(text: string): void {
    // Buffer or process text
  }

  async finalize(): Promise<void> {
    // Flush remaining audio
  }
}

See

• LiveTTSProvider for WebSocket-based streaming TTS
• RestTTSProvider for REST/batch TTS
• BaseProvider for the root provider lifecycle

Extends

• BaseProviderClass

Constructors

Constructor

new BaseTTSProvider(
   type, 
   config, 
   logger?): BaseTTSProvider;

Defined in: src/providers/base/BaseTTSProvider.ts:99

Create a new TTS provider.

Parameters

Returns

BaseTTSProvider

Overrides

BaseProviderClass.constructor

Properties

Accessors

isProxyMode

Get Signature

get protected isProxyMode(): boolean;

Defined in: src/providers/base/BaseProvider.ts:286

Whether the provider is in proxy mode.

Returns

boolean

true when proxyUrl is set.

Inherited from

BaseProviderClass.isProxyMode

Methods

assertAuth()

protected assertAuth(): void;

Defined in: src/providers/base/BaseProvider.ts:272

Validate that auth is configured (either apiKey or proxyUrl).

Returns

void

Remarks

Call this in onInitialize() for any provider that requires external authentication. Native providers (NativeSTT, NativeTTS) and in-browser providers (WebLLM) should NOT call this method.

Throws

ProviderInitializationError Thrown when neither apiKey nor proxyUrl is set.

Inherited from

BaseProviderClass.assertAuth

assertReady()

protected assertReady(): void;

Defined in: src/providers/base/BaseProvider.ts:255

Guard that throws if the provider has not been initialized.

Returns

void

Remarks

Call at the start of any method that requires the provider to be ready.

Throws

Error Thrown with a descriptive message when initialized is false.

Inherited from

BaseProviderClass.assertReady

dispose()

dispose(): Promise<void>;

Defined in: src/providers/base/BaseProvider.ts:154

Clean up resources and dispose of the provider.

Returns

Promise<void>

Remarks

Delegates to the subclass hook onDispose and resets the initialized flag. If the provider is not initialized, the call is a no-op.

Throws

Re-throws any error raised by onDispose.

Inherited from

BaseProviderClass.dispose

emitAudio()

protected emitAudio(chunk): void;

Defined in: src/providers/base/BaseTTSProvider.ts:190

Emit a synthesized audio chunk to the registered callback.

Parameters

Returns

void

Remarks

Subclasses call this method for each chunk of audio produced during synthesis. If no callback has been registered the chunk is silently dropped.

emitMetadata()

protected emitMetadata(metadata): void;

Defined in: src/providers/base/BaseTTSProvider.ts:206

Emit audio metadata to the registered callback.

Parameters

Returns

void

Remarks

Typically called once at the start of synthesis when the provider knows the output format. If no callback has been registered the metadata is silently dropped.

finalize()

abstract finalize(): Promise<void>;

Defined in: src/providers/base/BaseTTSProvider.ts:130

Finalize synthesis — flush remaining audio.

Returns

Promise<void>

Remarks

Called after all text has been sent via processChunk. The provider should ensure all buffered text is synthesized and all remaining audio chunks are emitted before resolving.

getConfig()

getConfig(): TTSProviderConfig;

Defined in: src/providers/base/BaseTTSProvider.ts:217

Get a shallow copy of the current TTS configuration.

Returns

TTSProviderConfig

A new TTSProviderConfig object.

Overrides

BaseProviderClass.getConfig

initialize()

initialize(): Promise<void>;

Defined in: src/providers/base/BaseProvider.ts:127

Initialize the provider, making it ready for use.

Returns

Promise<void>

Remarks

Calls the subclass hook onInitialize. If the provider has already been initialized the call is a no-op.

Throws

ProviderInitializationError Thrown when onInitialize rejects. The original error is wrapped with the provider class name for diagnostics.

Inherited from

BaseProviderClass.initialize

isAudioReady()

isAudioReady(chunk): boolean;

Defined in: src/providers/base/BaseTTSProvider.ts:145

Is this audio chunk ready for playback?

Parameters

Returns

boolean

true when the chunk has valid audio data.

Remarks

The orchestrator calls this to validate audio chunks before passing them to the audio player. The default implementation checks that the chunk has non-zero data.

isReady()

isReady(): boolean;

Defined in: src/providers/base/BaseProvider.ts:178

Check whether the provider has been initialized and is ready.

Returns

boolean

true when initialize has completed successfully and dispose has not yet been called.

Inherited from

BaseProviderClass.isReady

onAudio()

onAudio(callback): void;

Defined in: src/providers/base/BaseTTSProvider.ts:161

Register a callback to receive synthesized audio chunks.

Parameters

Returns

void

Remarks

All TTS providers — regardless of transport — deliver audio through this callback. CompositeVoice registers it during pipeline setup so that audio data flows into the AudioPlayer.

onConfigUpdate()

protected onConfigUpdate(_config): void;

Defined in: src/providers/base/BaseProvider.ts:242

Hook called after updateConfig merges new values.

Parameters

Returns

void

Remarks

The default implementation is a no-op. Override in subclasses to react to runtime configuration changes (e.g. reconnect with a new API key).

Inherited from

BaseProviderClass.onConfigUpdate

onDispose()

abstract protected onDispose(): Promise<void>;

Defined in: src/providers/base/BaseProvider.ts:229

Provider-specific disposal logic.

Returns

Promise<void>

Remarks

Subclasses must implement this method to release any resources acquired during onInitialize (e.g. close connections, free memory).

Inherited from

BaseProviderClass.onDispose

onInitialize()

abstract protected onInitialize(): Promise<void>;

Defined in: src/providers/base/BaseProvider.ts:217

Provider-specific initialization logic.

Returns

Promise<void>

Remarks

Subclasses must implement this method to perform any setup required before the provider can be used (e.g. validate credentials, open connections, load models).

Inherited from

BaseProviderClass.onInitialize

onMetadata()

onMetadata(callback): void;

Defined in: src/providers/base/BaseTTSProvider.ts:176

Register a callback to receive audio metadata.

Parameters

Returns

void

Remarks

Metadata (sample rate, encoding, channels, etc.) helps the AudioPlayer configure playback correctly. Providers may emit metadata once at the start of synthesis but are not required to.

processChunk()

abstract processChunk(text): void;

Defined in: src/providers/base/BaseTTSProvider.ts:118

Process a text chunk for synthesis.

Parameters

Returns

void

Remarks

Called by the orchestrator with text to synthesize. For live providers, this delegates to WebSocket send. For REST providers, this accumulates text into a buffer.

resolveApiKey()

protected resolveApiKey(): string;

Defined in: src/providers/base/BaseProvider.ts:325

Resolve the API key for this provider.

Returns

string

The configured API key, or 'proxy' in proxy mode.

Remarks

Returns 'proxy' in proxy mode so that SDK clients (which require a non-empty API key string) can be instantiated without the real key.

Inherited from

BaseProviderClass.resolveApiKey

resolveAuthHeader()

protected resolveAuthHeader(defaultAuthType?): string | undefined;

Defined in: src/providers/base/BaseProvider.ts:366

Resolve Authorization header value for the configured auth type.

Parameters

Returns

string | undefined

The Authorization header value, or undefined in proxy mode.

Remarks

Returns the header value for REST or server-side WebSocket connections:

• 'token' → 'Token <apiKey>'
• 'bearer' → 'Bearer <apiKey>'

Returns undefined in proxy mode.

Inherited from

BaseProviderClass.resolveAuthHeader

resolveBaseUrl()

protected resolveBaseUrl(defaultUrl?): string | undefined;

Defined in: src/providers/base/BaseProvider.ts:307

Resolve the base URL for this provider.

Parameters

Returns

string | undefined

The resolved URL, or undefined when all sources are unset.

Remarks

Priority: proxyUrl > endpoint > defaultUrl.

For WebSocket providers (this.type === 'websocket'), the proxy URL’s http(s) scheme is automatically converted to ws(s).

When no URL is configured and defaultUrl is undefined, the return value is undefined — this lets SDK-based providers (Anthropic, OpenAI) fall back to their own built-in defaults.

Inherited from

BaseProviderClass.resolveBaseUrl

resolveWsProtocols()

protected resolveWsProtocols(defaultAuthType?): string[] | undefined;

Defined in: src/providers/base/BaseProvider.ts:343

Resolve WebSocket subprotocol for authentication.

Parameters

Returns

string[] | undefined

Subprotocol array for new WebSocket(url, protocols), or undefined.

Remarks

Returns the subprotocol array for direct mode based on authType:

• 'token' → ['token', apiKey] (Deepgram default)
• 'bearer' → ['bearer', apiKey] (OAuth/Bearer tokens)

Returns undefined in proxy mode (no client-side auth needed).

Inherited from

BaseProviderClass.resolveWsProtocols

updateConfig()

updateConfig(config): void;

Defined in: src/providers/base/BaseProvider.ts:201

Merge partial configuration updates into the current config.

Parameters

Returns

void

Remarks

After merging, the subclass hook onConfigUpdate is called so providers can react to changed values at runtime.

Inherited from

BaseProviderClass.updateConfig