aolsenjazz/libsamplerate-js

/**
 * The entry point into this library. All of the actual resampling work is handled in src.ts
 */
import { SRC } from './src';
import { ConverterTypeValue, ConverterType } from './converter-type';
import LoadSRC from './glue';
import { ModuleType } from './module-type';

/**
 * Options that can be passed to create() when obtaining a copy of SRC.
 */
type CreateOptions = {
    converterType: ConverterTypeValue;
};

/**
 * Load the libsamplerate wasm module and wrap it in a SRC object.
 *
 * options = {
 *   converterType: {ConverterType} default SRC_SINC_FASTEST
 * }
 *
 * @param nChannels the number of output channels. 1-128 supported
 * @param inputSampleRate The sample rate of whatever source audio you want to resample
 * @param outputSampleRate If playing audio in-browser, this should be equal to AudioContext.sampleRate
 * @param options Additional configuration information. see above
 * @returns a promise containing the SRC object on resolve, or error message on error
 */
export async function create(
    nChannels: number,
    inputSampleRate: number,
    outputSampleRate: number,
    options?: CreateOptions
): Promise<SRC> {
    const cType =
        options?.converterType === undefined
            ? ConverterType.SRC_SINC_FASTEST
            : options?.converterType;

    validate(nChannels, inputSampleRate, outputSampleRate, cType);

    const loadedModule = LoadSRC();
    const src = new SRC(
        loadedModule as ModuleType,
        cType,
        nChannels,
        inputSampleRate,
        outputSampleRate
    );
    return src;
}

export { ConverterType };

/**
 * Validates the input data. Throws if data is invalid
 *
 * @param nChannels the number of output channels. 1-128 supported
 * @param inputSampleRate The sample rate of whatever source audio you want to resample
 * @param outputSampleRate If playing audio in-browser, this should be equal to AudioContext.sampleRate
 * @param cType ConverterType. See above
 */
function validate(
    nChannels: number,
    inputSampleRate: number,
    outputSampleRate: number,
    cType: ConverterTypeValue
) {
    if (nChannels === undefined) throw 'nChannels is undefined';
    if (inputSampleRate === undefined) throw 'inputSampleRate is undefined';
    if (outputSampleRate === undefined) throw 'outputSampleRate is undefined';

    if (nChannels < 1 || nChannels > 128) throw 'invalid nChannels submitted';
    if (inputSampleRate < 1 || inputSampleRate > 192000)
        throw 'invalid inputSampleRate';
    if (outputSampleRate < 1 || outputSampleRate > 192000)
        throw 'invalid outputSampleRate';
    if (
        cType < ConverterType.SRC_SINC_BEST_QUALITY ||
        cType > ConverterType.SRC_LINEAR
    )
        throw 'invalid converterType';
}

// Enables us to access this library in the `AudioWorkletGlobalScope` object via
// globalThis.LibSampleRate. This library should be loaded into the `AudioWorkletGlobalScope`
// with audioCtx.audioWorklet.addModule('@alexanderolsen/libsamplerate-js').
if (globalThis.constructor.name === 'AudioWorkletGlobalScope') {
    // eslint-disable-next-line @typescript-eslint/no-explicit-any
    (globalThis as any).LibSampleRate = {
        create,
        ConverterType,
    };
}