/**
 * @license
 * Copyright 2021 Google LLC. All Rights Reserved.
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * =============================================================================
 */
/**
 * A stateful filter that smoothes values overtime.
 *
 * More specifically, it stores the previous value, and when there's a new
 * value, a coefficient 'alpha' is applied to the new value, and `1 - alpha` is
 * applied to the previous value. The smaller the alpha is, the smoother result
 * and the bigger lag.
 */
export declare class LowPassFilter {
    private alpha;
    private initialized;
    private rawValue;
    private storedValue;
    constructor(alpha: number);
    apply(value: number, threshold?: number): number;
    applyWithAlpha(value: number, alpha: number, threshold?: number): number;
    hasLastRawValue(): boolean;
    lastRawValue(): number;
    reset(): void;
}