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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.
*/
import { useRef } from "react";
import logger from "../utils/logger";
const AUDIO_BUFFER_LENGTH_SEC = 120;
const INITIAL_SAMPLE_RATE = 16_000;
// Don't start the audio before the buffer has at least this much data.
// If we start immediately, the audio chunks arrive too late to play
// in real time and cause choppy audio, especially in high-latency environments.
const MIN_BUFFER_DURATION_BEFORE_START_SEC = 0.8;
class AudioPlayer {
private timerID: ReturnType<typeof setTimeout> | null = null;
private offset: number = 0;
private currentAudioSequenceDuration: number = 0;
private currentAudioSequenceStartedAt: number = 0;
private audioBuffer: AudioBuffer;
private source: AudioBufferSourceNode;
private audioCtx = new AudioContext({ sampleRate: INITIAL_SAMPLE_RATE });
private timeUntilAudioCompleted: number = 0;
constructor() {
this.audioBuffer = this.createNewAudioBuffer();
this.source = this.audioCtx.createBufferSource();
this.source.buffer = this.audioBuffer;
this.source.connect(this.audioCtx.destination);
}
play(chunk: AudioBuffer): void {
const channel = this.audioBuffer.getChannelData(0); // mono channel
const buffer = chunk.getChannelData(0);
if (chunk.sampleRate !== this.audioCtx.sampleRate) {
this.audioCtx = new AudioContext({ sampleRate: chunk.sampleRate });
logger.log(
`New sample rate ${this.audioCtx.sampleRate}. Resetting buffer`
);
this.reset();
}
// We receive the data in unsigned 16-bit words. AudioBuffer must
// be in 32-bit floats between -1.0 and 1.0. To convert, normalize
// each sample
for (let i = 0; i < buffer.length; i++) {
channel[i + this.offset] = buffer[i];
}
this.offset += buffer.length;
// We set a timer that will reset the audio buffer after the audio sequence has been
// played. We cannot predetermine the duration of the audio sequence, because more
// audio chunks may be added after the audio has started playing. For this reason,
// every time a chunk is added to the buffer, we clear the existing timer, recompute
// the duration of the audio sequence, and create a new timer with the appropriate
// audio sequence duration.
if (this.timerID) {
clearTimeout(this.timerID);
}
const chunkDuration = buffer.length / this.audioCtx.sampleRate;
this.currentAudioSequenceDuration += chunkDuration;
// If this is the first chunk of audio since the player was last reset, immediately
// start playing the source. Additional chunks will be appended to the buffer as
// they come
if (!this.currentAudioSequenceStartedAt) {
if (
this.currentAudioSequenceDuration < MIN_BUFFER_DURATION_BEFORE_START_SEC
) {
logger.warn(
`The current buffer is too short ${this.currentAudioSequenceDuration} seconds) to start the audio. Waiting for more chunks...`
);
return;
}
this.currentAudioSequenceStartedAt = performance.now();
this.source.start();
}
const audioEllapsed =
(performance.now() - this.currentAudioSequenceStartedAt) / 1000;
this.timeUntilAudioCompleted =
this.currentAudioSequenceDuration - audioEllapsed;
this.timerID = setTimeout(() => {
this.reset();
}, this.timeUntilAudioCompleted * 1000);
}
private createNewAudioBuffer(): AudioBuffer {
return this.audioCtx.createBuffer(
1,
this.audioCtx.sampleRate * AUDIO_BUFFER_LENGTH_SEC,
this.audioCtx.sampleRate
);
}
private reset(): void {
logger.log("reset");
if (this.source) {
try {
this.source.stop();
this.source.disconnect();
} catch {
// Ignore errors if source was already stopped
}
}
this.offset = 0;
this.currentAudioSequenceDuration = 0;
this.currentAudioSequenceStartedAt = 0;
this.timeUntilAudioCompleted = 0;
if (this.timerID) {
clearTimeout(this.timerID);
this.timerID = null;
}
this.audioBuffer = this.createNewAudioBuffer();
this.source = this.audioCtx.createBufferSource();
this.source.buffer = this.audioBuffer;
this.source.connect(this.audioCtx.destination);
}
public getSource(): AudioBufferSourceNode {
return this.source;
}
// Immediately stops playing audio. Audio left in the buffer is erased
public interrupt(): void {
if (this.timerID) {
clearTimeout(this.timerID);
}
this.reset();
}
}
export default function useAudioPlayer(): AudioPlayer {
const audioPlayerRef = useRef<AudioPlayer>(null);
if (!audioPlayerRef.current) {
audioPlayerRef.current = new AudioPlayer();
}
return audioPlayerRef.current;
}
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