鸿蒙媒体开发系列08——AudioCapturer录制音频
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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
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releaseif (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');}}}