/** Encode a single 16-bit linear PCM sample to an 8-bit μ-law byte. */
export declare const encodeMulawSample: (pcmSample: number) => number;
/** Decode a single 8-bit μ-law byte back to a 16-bit linear PCM sample. */
export declare const decodeMulawSample: (mulawByte: number) => number;
/** Decode a base64 μ-law payload (Twilio media frame) to 16-bit PCM. */
export declare const decodeMulawBase64: (payload: string) => Int16Array;
/** Encode 16-bit linear PCM to a base64 μ-law payload (Twilio media frame). */
export declare const encodeMulawBase64: (samples: Int16Array) => string;
/**
 * Resample 16-bit PCM from `fromHz` to `toHz` using linear interpolation.
 * Good enough for telephony (8 kHz target, where the lowpass artifacts are
 * masked by the codec anyway). The receptionist bridge uses the same trick.
 */
export declare const resamplePcm: (input: Int16Array, fromHz: number, toHz: number) => Int16Array;
/**
 * Split a PCM stream into 20 ms frames (160 samples @ 8 kHz). Twilio Media
 * Streams expects this packetization — sending larger chunks works but pacing
 * becomes a problem on the playback side.
 */
export declare const frame20ms8k: (samples: Int16Array) => Int16Array[];
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