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1、概述
我们在鸿蒙媒体开发系列07——AVRecorder音频录制中我们了解到,HarmonyOS提供了三种录制音频的方式:AVRecorder、AudioCapturer、OpenSL ES。并且介绍了AVRecorder的基本用法,本文中我们将了解AudioCapturer的使用。
AudioCapturer是音频采集器,用于录制PCM(Pulse Code Modulation)音频数据,适合有音频开发经验的开发者实现更灵活的录制功能。
2、核心状态与状态变化关系
使用AudioCapturer录制音频涉及到AudioCapturer实例的创建、音频采集参数的配置、采集的开始与停止、资源的释放等。本文将以一次录制音频数据的过程为例,探讨如何使用AudioCapturer进行音频录制。
在创建实例后,调用对应的方法可以进入指定的状态实现对应的行为。需要注意的是在确定的状态执行不合适的方法可能导致AudioCapturer发生错误,建议在调用状态转换的方法前进行状态检查,避免程序运行产生预期以外的结果。
AudioCapturer状态变化示意图如下
使用on('stateChange')方法可以监听AudioCapturer的状态变化,每个状态对应值与说明如下:
3、开发步骤介绍
1、配置音频采集参数并创建AudioCapturer实例。
import audio from '@ohos.multimedia.audio';
let audioStreamInfo = {
samplingRate: audio.AudioSamplingRate.SAMPLE_RATE_44100,
channels: audio.AudioChannel.CHANNEL_2,
sampleFormat: audio.AudioSampleFormat.SAMPLE_FORMAT_S16LE,
encodingType: audio.AudioEncodingType.ENCODING_TYPE_RAW
};
let audioCapturerInfo = {
source: audio.SourceType.SOURCE_TYPE_MIC,
capturerFlags: 0
};
let audioCapturerOptions = {
streamInfo: audioStreamInfo,
capturerInfo: audioCapturerInfo
};
audio.createAudioCapturer(audioCapturerOptions, (err, data) => {
if (err) {
console.error(`Invoke createAudioCapturer failed, code is ${err.code}, message is ${err.message}`);
} else {
console.info('Invoke createAudioCapturer succeeded.');
let audioCapturer = data;
}
});
其中,AudioCapturerOptions是一个构造配置入参,类图如下所示(点击看大图):
2、调用start()方法进入running状态,开始录制音频。
audioCapturer.start((err) => {
if (err) {
console.error(`Capturer start failed, code is ${err.code}, message is ${err.message}`);
} else {
console.info('Capturer start success.');
}
});
3、指定录制文件地址,调用read()方法读取缓冲区的数据。
let file = fs.openSync(path, 0o2 | 0o100);
let bufferSize = await audioCapturer.getBufferSize();
let buffer = await audioCapturer.read(bufferSize, true);
fs.writeSync(file.fd, buffer);
4、调用stop()方法停止录制。
audioCapturer.stop((err) => {
if (err) {
console.error(`Capturer stop failed, code is ${err.code}, message is ${err.message}`);
} else {
console.info('Capturer stopped.');
}
});
5、 调用release()方法销毁实例,释放资源。
audioCapturer.release((err) => {
if (err) {
console.error(`capturer release failed, code is ${err.code}, message is ${err.message}`);
} else {
console.info('capturer released.');
}
});
使用AudioCapturer录制音频的完整示例代码如下:
import audio from '@ohos.multimedia.audio';
import fs from '@ohos.file.fs';
const TAG = 'AudioCapturerDemo';
export default class AudioCapturerDemo {
private audioCapturer = undefined;
private audioStreamInfo = {
samplingRate: audio.AudioSamplingRate.SAMPLE_RATE_44100,
channels: audio.AudioChannel.CHANNEL_1,
sampleFormat: audio.AudioSampleFormat.SAMPLE_FORMAT_S16LE,
encodingType: audio.AudioEncodingType.ENCODING_TYPE_RAW
}
private audioCapturerInfo = {
source: audio.SourceType.SOURCE_TYPE_MIC, // 音源类型
capturerFlags: 0 // 音频采集器标志
}
private audioCapturerOptions = {
streamInfo: this.audioStreamInfo,
capturerInfo: this.audioCapturerInfo
}
// 初始化,创建实例,设置监听事件
init() {
audio.createAudioCapturer(this.audioCapturerOptions, (err, capturer) => { // 创建AudioCapturer实例
if (err) {
console.error(`Invoke createAudioCapturer failed, code is ${err.code}, message is ${err.message}`);
return;
}
console.info(`${TAG}: create AudioCapturer success`);
this.audioCapturer = capturer;
this.audioCapturer.on('markReach', 1000, (position) => { // 订阅markReach事件,当采集的帧数达到1000时触发回调
if (position === 1000) {
console.info('ON Triggered successfully');
}
});
this.audioCapturer.on('periodReach', 2000, (position) => { // 订阅periodReach事件,当采集的帧数达到2000时触发回调
if (position === 2000) {
console.info('ON Triggered successfully');
}
});
});
}
// 开始一次音频采集
async start() {
let stateGroup = [audio.AudioState.STATE_PREPARED, audio.AudioState.STATE_PAUSED, audio.AudioState.STATE_STOPPED];
if (stateGroup.indexOf(this.audioCapturer.state) === -1) { // 当且仅当状态为STATE_PREPARED、STATE_PAUSED和STATE_STOPPED之一时才能启动采集
console.error(`${TAG}: start failed`);
return;
}
await this.audioCapturer.start(); // 启动采集
let context = getContext(this);
const path = context.filesDir + '/test.wav'; // 采集到的音频文件存储路径
let file = fs.openSync(path, 0o2 | 0o100); // 如果文件不存在则创建文件
let fd = file.fd;
let numBuffersToCapture = 150; // 循环写入150次
let count = 0;
while (numBuffersToCapture) {
let bufferSize = await this.audioCapturer.getBufferSize();
let buffer = await this.audioCapturer.read(bufferSize, true);
let options = {
offset: count * bufferSize,
length: bufferSize
};
if (buffer === undefined) {
console.error(`${TAG}: read buffer failed`);
} else {
let number = fs.writeSync(fd, buffer, options);
console.info(`${TAG}: write date: ${number}`);
}
numBuffersToCapture--;
count++;
}
}
// 停止采集
async stop() {
// 只有采集器状态为STATE_RUNNING或STATE_PAUSED的时候才可以停止
if (this.audioCapturer.state !== audio.AudioState.STATE_RUNNING && this.audioCapturer.state !== audio.AudioState.STATE_PAUSED) {
console.info('Capturer is not running or paused');
return;
}
await this.audioCapturer.stop(); // 停止采集
if (this.audioCapturer.state === audio.AudioState.STATE_STOPPED) {
console.info('Capturer stopped');
} else {
console.error('Capturer stop failed');
}
}
// 销毁实例,释放资源
async release() {
// 采集器状态不是STATE_RELEASED或STATE_NEW状态,才能release
if (this.audioCapturer.state === audio.AudioState.STATE_RELEASED || this.audioCapturer.state === audio.AudioState.STATE_NEW) {
console.info('Capturer already released');
return;
}
await this.audioCapturer.release(); // 释放资源
if (this.audioCapturer.state == audio.AudioState.STATE_RELEASED) {
console.info('Capturer released');
} else {
console.error('Capturer release failed');
}
}
}