使用AudioCapturer开发音频录制功能

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。

开发指导

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。本开发指导将以一次录制音频数据的过程为例，向开发者讲解如何使用AudioCapturer进行音频录制，建议搭配AudioCapturer的API说明阅读。

下图展示了AudioCapturer的状态变化，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，建议开发者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。

图1 AudioCapturer状态变化示意图 AudioCapturer status change

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见AudioState。

开发步骤及注意事项

配置音频采集参数并创建AudioCapturer实例，音频采集参数的详细信息可以查看AudioCapturerOptions。

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;
  }
});

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.');
  }
});

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);

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.');
  }
});

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.');
  }
});

完整示例

下面展示了使用AudioCapturer录制音频的完整示例代码。

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');
    }
  }
}