音频采集开发指导


音频采集开发指导

简介

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接口的调用实现音频数据的采集。

  • 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。

运作机制

该模块提供了音频采集模块的状态变化示意图。

图1 音频采集状态变化示意图

audio-capturer-state

PREPARED状态: 通过调用create()方法进入到该状态。
RUNNING状态: 正在进行音频数据播放,可以在prepared状态通过调用start()方法进入此状态,也可以在stopped状态通过调用start()方法进入此状态。
STOPPED状态: 在running状态可以通过stop()方法停止音频数据的播放。
RELEASED状态: 在prepared和stop状态,用户均可通过release()方法释放掉所有占用的硬件和软件资源,并且不会再进入到其他的任何一种状态了。

约束与限制

开发者在进行音频数据采集功能开发前,需要先对所开发的应用配置麦克风权限(ohos.permission.MICROPHONE),权限配置相关内容可参考:访问控制授权申请指导

开发指导

详细API含义可参考:音频管理API文档AudioCapturer

  1. 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。

    import audio from '@ohos.multimedia.audio';
    
    let audioStreamInfo = {
      samplingRate: audio.AudioSamplingRate.SAMPLE_RATE_44100,
      channels: audio.AudioChannel.CHANNEL_1,
      sampleFormat: audio.AudioSampleFormat.SAMPLE_FORMAT_S16LE,
      encodingType: audio.AudioEncodingType.ENCODING_TYPE_RAW
    }
    
    let audioCapturerInfo = {
      source: audio.SourceType.SOURCE_TYPE_MIC,
      capturerFlags: 0 // 0是音频采集器的扩展标志位,默认为0
    }
    
    let audioCapturerOptions = {
      streamInfo: audioStreamInfo,
      capturerInfo: audioCapturerInfo
    }
    
    let audioCapturer = await audio.createAudioCapturer(audioCapturerOptions);
    console.log('AudioRecLog: Create audio capturer success.');
    
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  2. 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。

    import audio from '@ohos.multimedia.audio';
    
    async function startCapturer() {
      let state = audioCapturer.state;
      // Capturer start时的状态应该是STATE_PREPARED、STATE_PAUSED和STATE_STOPPED之一.
      if (state != audio.AudioState.STATE_PREPARED || state != audio.AudioState.STATE_PAUSED ||
        state != audio.AudioState.STATE_STOPPED) {
        console.info('Capturer is not in a correct state to start');
        return;
      }
      await audioCapturer.start();
    
      let state = audioCapturer.state;
      if (state == audio.AudioState.STATE_RUNNING) {
        console.info('AudioRecLog: Capturer started');
      } else {
        console.error('AudioRecLog: Capturer start failed');
      }
    }
    
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  3. 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';
    
     let state = audioCapturer.state;
     // 只有状态为STATE_RUNNING的时候才可以read.
     if (state != audio.AudioState.STATE_RUNNING) {
       console.info('Capturer is not in a correct state to read');
       return;
     }
       
    const path = '/data/data/.pulse_dir/capture_js.wav'; // 采集到的音频文件存储路径
    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');
    }
       
    let numBuffersToCapture = 150; // 循环写入150次
    while (numBuffersToCapture) {
      let buffer = await audioCapturer.read(bufferSize, true);
      if (typeof(buffer) == undefined) {
        console.info('AudioRecLog: read buffer failed');
      } else {
        let number = fileio.writeSync(fd, buffer);
        console.info(`AudioRecLog: data written: ${number}`);
      }
       
      numBuffersToCapture--;
    }
    
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  4. 采集完成后,调用stop方法,停止录制。

     async function StopCapturer() {
       let state = audioCapturer.state;
       // 只有采集器状态为STATE_RUNNING或STATE_PAUSED的时候才可以停止
       if (state != audio.AudioState.STATE_RUNNING && state != audio.AudioState.STATE_PAUSED) {
         console.info('AudioRecLog: Capturer is not running or paused');
         return;
       }
    
       await audioCapturer.stop();
    
       state = audioCapturer.state;
       if (state == audio.AudioState.STATE_STOPPED) {
         console.info('AudioRecLog: Capturer stopped');
       } else {
         console.error('AudioRecLog: Capturer stop failed');
       }
     }
    
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  5. 任务结束,调用release()方法释放相关资源。

     async function releaseCapturer() {
       let state = audioCapturer.state;
       // 采集器状态不是STATE_RELEASED或STATE_NEW状态,才能release
       if (state == audio.AudioState.STATE_RELEASED || state == audio.AudioState.STATE_NEW) {
         console.info('AudioRecLog: Capturer already released');
         return;
       }
    
       await audioCapturer.release();
    
       state = audioCapturer.state;
       if (state == audio.AudioState.STATE_RELEASED) {
         console.info('AudioRecLog: Capturer released');
       } else {
         console.info('AudioRecLog: Capturer release failed');
       }
     }
    
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  6. (可选)获取采集器相关信息

    通过以下代码,可以获取采集器的相关信息。

    // 获取当前采集器状态
    let state = audioCapturer.state;
    
    // 获取采集器信息
    let audioCapturerInfo : audio.AuduioCapturerInfo = await audioCapturer.getCapturerInfo();
    
    // 获取音频流信息
    let audioStreamInfo : audio.AudioStreamInfo = await audioCapturer.getStreamInfo();
    
    // 获取音频流ID
    let audioStreamId : number = await audioCapturer.getAudioStreamId();
    
    // 获取纳秒形式的Unix时间戳
    let audioTime : number = await audioCapturer.getAudioTime();
    
    // 获取合理的最小缓冲区大小
    let bufferSize : number = await audioCapturer.getBuffersize();
    
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  7. (可选)使用on('markReach')方法订阅采集器标记到达事件,使用off('markReach')取消订阅事件。

    注册markReach监听后,当采集器采集的帧数到达设定值时,会触发回调并返回设定的值。

    audioCapturer.on('markReach', (reachNumber) => {
      console.info('Mark reach event Received');
      console.info(`The Capturer reached frame: ${reachNumber}`);
    });
    
    audioCapturer.off('markReach'); // 取消markReach事件的订阅,后续将无法监听到“标记到达”事件
    
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  8. (可选)使用on('periodReach')方法订阅采集器区间标记到达事件,使用off('periodReach')取消订阅事件。

    注册periodReach监听后,每当采集器采集的帧数到达设定值时,会触发回调并返回设定的值。

    audioCapturer.on('periodReach', (reachNumber) => {
      console.info('Period reach event Received');
      console.info(`In this period, the Capturer reached frame: ${reachNumber}`);
    });
    
    audioCapturer.off('periodReach'); // 取消periodReach事件的订阅,后续将无法监听到“区间标记到达”事件
    
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  9. 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,当采集器状态更新时,会受到一个包含有事件类型的回调。

    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;
      }
    });
    
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