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

  1. 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: audio.AudioStreamInfo = {
   samplingRate: audio.AudioSamplingRate.SAMPLE_RATE_48000, // 采样率
   channels: audio.AudioChannel.CHANNEL_2, // 通道
   sampleFormat: audio.AudioSampleFormat.SAMPLE_FORMAT_S16LE, // 采样格式
   encodingType: audio.AudioEncodingType.ENCODING_TYPE_RAW // 编码格式
 };
 
 let audioCapturerInfo: audio.AudioCapturerInfo = {
   source: audio.SourceType.SOURCE_TYPE_MIC,
   capturerFlags: 0
 };
 
 let audioCapturerOptions: audio.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;
   }
 });

  2. 调用on('readData')方法，订阅监听音频数据读入回调。

     import { BusinessError } from '@ohos.base';
 import fs from '@ohos.file.fs';

 let bufferSize: number = 0;
 class Options {
   offset?: number;
   length?: number;
 }
 let readDataCallback = (buffer: ArrayBuffer) => {
   let path = getContext().cacheDir;
   let filePath = path + '/StarWars10s-2C-48000-4SW.wav';
   let file: fs.File = fs.openSync(filePath, fs.OpenMode.READ_WRITE | fs.OpenMode.CREATE);
   let options: Options = {
     offset: bufferSize,
     length: buffer.byteLength
   }
   fs.writeSync(file.fd, buffer, options);
   bufferSize += buffer.byteLength;
 }
 audioCapturer.on('readData', readDataCallback);

  3. 调用start()方法进入running状态，开始录制音频。

     import { BusinessError } from '@ohos.base';

 audioCapturer.start((err: BusinessError) => {
   if (err) {
     console.error(`Capturer start failed, code is ${err.code}, message is ${err.message}`);
   } else {
     console.info('Capturer start success.');
   }
 });

  4. 调用stop()方法停止录制。

     import { BusinessError } from '@ohos.base';

 audioCapturer.stop((err: BusinessError) => {
   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。

     import { BusinessError } from '@ohos.base';

 audioCapturer.release((err: BusinessError) => {
   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 { BusinessError } from '@ohos.base';
import fs from '@ohos.file.fs';

const TAG = 'AudioCapturerDemo';

class Options {
  offset?: number;
  length?: number;
}

let context = getContext(this);
let bufferSize: number = 0;
let audioCapturer: audio.AudioCapturer | undefined = undefined;
let audioStreamInfo: audio.AudioStreamInfo = {
  samplingRate: audio.AudioSamplingRate.SAMPLE_RATE_48000, // 采样率
  channels: audio.AudioChannel.CHANNEL_2, // 通道
  sampleFormat: audio.AudioSampleFormat.SAMPLE_FORMAT_S16LE, // 采样格式
  encodingType: audio.AudioEncodingType.ENCODING_TYPE_RAW // 编码格式
}
let audioCapturerInfo: audio.AudioCapturerInfo = {
  source: audio.SourceType.SOURCE_TYPE_MIC, // 音源类型
  capturerFlags: 0 // 音频采集器标志
}
let audioCapturerOptions: audio.AudioCapturerOptions = {
  streamInfo: audioStreamInfo,
  capturerInfo: audioCapturerInfo
}
let readDataCallback = (buffer: ArrayBuffer) => {
   let path = getContext().cacheDir;
   let filePath = path + '/StarWars10s-2C-48000-4SW.wav';
   let file: fs.File = fs.openSync(filePath, fs.OpenMode.READ_WRITE | fs.OpenMode.CREATE);
   let options: Options = {
      offset: bufferSize,
      length: buffer.byteLength
   }
   fs.writeSync(file.fd, buffer, options);
   bufferSize += buffer.byteLength;
}

// 初始化，创建实例，设置监听事件
function init() {
  audio.createAudioCapturer(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`);
    audioCapturer = capturer;
    if (audioCapturer !== undefined) {
       (audioCapturer as audio.AudioCapturer).on('readData', readDataCallback);
    }
  });
}

// 开始一次音频采集
function start() {
  if (audioCapturer !== undefined) {
    let stateGroup = [audio.AudioState.STATE_PREPARED, audio.AudioState.STATE_PAUSED, audio.AudioState.STATE_STOPPED];
    if (stateGroup.indexOf((audioCapturer as audio.AudioCapturer).state.valueOf()) === -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;
    }

    // 启动采集
    (audioCapturer as audio.AudioCapturer).start((err: BusinessError) => {
      if (err) {
        console.error('Capturer start failed.');
      } else {
        console.info('Capturer start success.');
      }
    });
  }
}

// 停止采集
function stop() {
  if (audioCapturer !== undefined) {
    // 只有采集器状态为STATE_RUNNING或STATE_PAUSED的时候才可以停止
    if ((audioCapturer as audio.AudioCapturer).state.valueOf() !== audio.AudioState.STATE_RUNNING && (audioCapturer as audio.AudioCapturer).state.valueOf() !== audio.AudioState.STATE_PAUSED) {
      console.info('Capturer is not running or paused');
      return;
    }

    //停止采集
    (audioCapturer as audio.AudioCapturer).stop((err: BusinessError) => {
      if (err) {
        console.error('Capturer stop failed.');
      } else {
        console.info('Capturer stop success.');
      }
    });
  }
}

// 销毁实例，释放资源
function release() {
  if (audioCapturer !== undefined) {
    // 采集器状态不是STATE_RELEASED或STATE_NEW状态，才能release
    if ((audioCapturer as audio.AudioCapturer).state.valueOf() === audio.AudioState.STATE_RELEASED || (audioCapturer as audio.AudioCapturer).state.valueOf() === audio.AudioState.STATE_NEW) {
      console.info('Capturer already released');
      return;
    }

    //释放资源
    (audioCapturer as audio.AudioCapturer).release((err: BusinessError) => {
      if (err) {
        console.error('Capturer release failed.');
      } else {
        console.info('Capturer release success.');
      }
    });
  }
}