/**
 * Linear sample-rate conversion — pure, dependency-free, browser-safe.
 *
 * The audio WebSocket carries 8 kHz μ-law, but a browser `AudioContext`
 * typically runs at 48 kHz (sometimes 44.1 kHz). These helpers bridge the gap:
 *
 *   - capture path:  downsample(captureRate → 8000) then μ-law encode
 *   - playback path: μ-law decode then upsample(8000 → playbackRate)
 *
 * Linear interpolation is intentionally simple. It is NOT a brick-wall
 * anti-alias filter — for an 8 kHz voice band downsampled from 48 kHz the
 * aliasing is mild and speech-intelligible, which is the right trade-off for a
 * dependency-free SDK hot path. (The `AudioWorklet` additionally benefits from
 * the browser's own resampling at the graph boundary.)
 *
 * Both functions are referentially transparent (no shared state, no
 * allocation beyond the returned array), so they are unit-testable without a
 * browser and safe to call per audio frame.
 */
/**
 * Resample a block of mono Float32 PCM samples from `fromRate` to `toRate`
 * using linear interpolation.
 *
 * The output length is `round(input.length * toRate / fromRate)`. Edge samples
 * are clamped (no out-of-range reads). When `fromRate === toRate` the input is
 * returned as a copy.
 */
export declare function resampleLinear(input: Float32Array, fromRate: number, toRate: number): Float32Array;
/**
 * Downsample to 8 kHz. Thin wrapper around {@link resampleLinear} for the
 * capture path (any context rate → 8000).
 */
export declare function downsampleTo8k(input: Float32Array, fromRate: number): Float32Array;
/**
 * Upsample from 8 kHz. Thin wrapper around {@link resampleLinear} for the
 * playback path (8000 → any context rate).
 */
export declare function upsampleFrom8k(input: Float32Array, toRate: number): Float32Array;
/**
 * Convert Float32 PCM in [-1, 1] to signed 16-bit PCM. Values outside the
 * range are clamped. Pure; returns a fresh `Int16Array`.
 */
export declare function floatToInt16(input: Float32Array): Int16Array;
/**
 * Convert signed 16-bit PCM to Float32 in [-1, 1]. Pure; returns a fresh
 * `Float32Array`.
 */
export declare function int16ToFloat(input: Int16Array): Float32Array;