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/*
* SPDX-FileCopyrightText: Copyright (c) 2024 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
* SPDX-License-Identifier: Apache-2.0
*
* 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
*
* http://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.
*/
class LinearPCMProcessor extends AudioWorkletProcessor {
// The size of the buffer in miliseconds. An audio block is posted to the main thread
// every time the buffer is full, which means a large buffer will emit less frequently
// (higher latency), but more efficiently (fewer I/O interruptions between the worker
// and the main thread)
static BUFFER_SIZE_MS = 32;
constructor() {
super();
// the "sampleRate" is available on the global scope in AudioWorklet files. The linter
// doesn't know that, so it incorrectly raises an error when accessing it. The comment
// below disables the linter for that specific line.
const rate = sampleRate;
const bufferSize = (rate / 1000) * LinearPCMProcessor.BUFFER_SIZE_MS;
this.buffer = new Int16Array(bufferSize);
this.offset = 0;
}
/**
* Converts input data from Float32Array to Int16Array, and stores it to
* to the buffer. When the buffer is full, its content is posted to the main
* thread, and the buffer is emptied
*/
process(inputList, _outputList, _parameters) {
// Assumes the input is mono (1 channel). If there are more channels, they
// are ignored
const input = inputList[0][0]; // first channel of first input
for (let i = 0; i < input.length; i++) {
const sample = Math.max(-1, Math.min(1, input[i]));
this.buffer[i + this.offset] =
sample < 0 ? sample * 0x8000 : sample * 0x7fff;
}
this.offset += input.length;
// Once the buffer is filled entirely, flush the buffer
if (this.offset >= this.buffer.length - 1) {
this.flush();
}
return true;
}
/**
* Sends the buffer's content to the main thread via postMessage(), and reset
* the offset to 0
*/
flush() {
this.offset = 0;
this.port.postMessage(this.buffer);
}
}
registerProcessor("linear-pcm-processor", LinearPCMProcessor);
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