音频采集开发指导

场景介绍

AudioCapturer提供了用于获取原始音频文件的方法。开发者可以通过本指导了解应用如何通过AudioCapturer采集音频。

状态检查

在进行应用开发的过程中，建议开发者通过on('stateChange')方法订阅AudioCapturer的状态变更。因为针对AudioCapturer的某些操作，仅在音频采集器在固定状态时才能执行。如果应用在音频采集器处于错误状态时执行操作，系统可能会抛出异常或生成其他未定义的行为。

详细API含义可参考：音频管理API文档AudioCapturer

图1 音频采集状态机

开发步骤

使用createAudioCapturer()创建一个AudioCapturer实例。

在audioCapturerOptions中设置音频采集器的相关参数。该实例可用于音频采集、控制和获取采集状态，以及注册通知回调。

   var audioStreamInfo = {
        samplingRate: audio.AudioSamplingRate.SAMPLE_RATE_44100,
        channels: audio.AudioChannel.CHANNEL_1,
        sampleFormat: audio.AudioSampleFormat.SAMPLE_FORMAT_S16LE,
        encodingType: audio.AudioEncodingType.ENCODING_TYPE_RAW
    }
   
    var audioCapturerInfo = {
        source: audio.SourceType.SOURCE_TYPE_MIC,
        capturerFlags: 1
    }
   
    var audioCapturerOptions = {
        streamInfo: audioStreamInfo,
        capturerInfo: audioCapturerInfo
    }
   
    let audioCapturer = await audio.createAudioCapturer(audioCapturerOptions);
    var state = audioRenderer.state;

（可选）使用on（'stateChange'）订阅音频采集器状态更改。如果应用需要在采集器状态更新时进行一些操作，可以订阅该事件。更多事件请参考API参考文档。

 audioCapturer.on('stateChange',(state) => {
 console.info('AudioCapturerLog: Changed State to : ' + state)
 switch (state) {
  case audio.AudioState.STATE_PREPARED:
      console.info('--------CHANGE IN AUDIO STATE----------PREPARED--------------');
      console.info('Audio State is : Prepared');
      break;
  case audio.AudioState.STATE_RUNNING:
      console.info('--------CHANGE IN AUDIO STATE----------RUNNING--------------');
      console.info('Audio State is : Running');
      break;
  case audio.AudioState.STATE_STOPPED:
      console.info('--------CHANGE IN AUDIO STATE----------STOPPED--------------');
      console.info('Audio State is : stopped');
      break;
  case audio.AudioState.STATE_RELEASED:
      console.info('--------CHANGE IN AUDIO STATE----------RELEASED--------------');
      console.info('Audio State is : released');
      break;
  default:
      console.info('--------CHANGE IN AUDIO STATE----------INVALID--------------');
      console.info('Audio State is : invalid');
      break;
  }
 });

调用start()方法来启动/恢复采集任务。

启动完成后，采集器状态将变更为STATE_RUNNING，然后应用可以开始读取缓冲区。

await audioCapturer.start();
if (audioCapturer.state == audio.AudioState.STATE_RUNNING) {
    console.info('AudioRecLog: Capturer started');
} else {
    console.info('AudioRecLog: Capturer start failed');
}

使用getBufferSize()方法获取要读取的最小缓冲区大小。

var bufferSize = await audioCapturer.getBufferSize();
console.info('AudioRecLog: buffer size: ' + bufferSize);

读取采集器的音频数据并将其转换为字节流。重复调用read()方法读取数据，直到应用准备停止采集。

参考以下示例，将采集到的数据写入文件。

import fileio from '@ohos.fileio';
   
const path = '/data/data/.pulse_dir/capture_js.wav';
let fd = fileio.openSync(path, 0o102, 0o777);
if (fd !== null) {
    console.info('AudioRecLog: file fd created');
}
else{
    console.info('AudioRecLog: file fd create : FAILED');
    return;
}
   
fd = fileio.openSync(path, 0o2002, 0o666);
if (fd !== null) {
    console.info('AudioRecLog: file fd opened in append mode');
}
   
var numBuffersToCapture = 150;
while (numBuffersToCapture) {
    var buffer = await audioCapturer.read(bufferSize, true);
    if (typeof(buffer) == undefined) {
        console.info('read buffer failed');
    } else {
        var number = fileio.writeSync(fd, buffer);
        console.info('AudioRecLog: data written: ' + number);
    }
   
    numBuffersToCapture--;
}

采集完成后，调用stop方法，停止录制。

await audioCapturer.stop();
if (audioCapturer.state == audio.AudioState.STATE_STOPPED) {
    console.info('AudioRecLog: Capturer stopped');
} else {
    console.info('AudioRecLog: Capturer stop failed');
}

任务结束，调用release()方法释放相关资源。

await audioCapturer.release();
if (audioCapturer.state == audio.AudioState.STATE_RELEASED) {
    console.info('AudioRecLog: Capturer released');
} else {
    console.info('AudioRecLog: Capturer release failed');
}