AudioRenderer怎么播放PCM音频流
=======================

#### 问题现象

AudioRenderer怎么直接播放PCM音频流，音频流可能是网络返回的，或者代码生成的，而不是PCM文件？

#### 背景知识

[AudioRenderer](https://developer.huawei.com/consumer/cn/doc/harmonyos-guides/using-audiorenderer-for-playback)是音频渲染器，用于播放PCM（Pulse Code Modulation）音频数据，相比AVPlayer而言，可以在输入前添加数据预处理，更适合有音频开发经验的开发者，以实现更灵活的播放功能。

#### 解决方案

AudioRenderer可通过[on('writeData')](https://developer.huawei.com/consumer/cn/doc/harmonyos-references/arkts-apis-audio-audiorenderer#onwritedata11)监听音频数据写入回调事件，如下示例介绍直接播放音频数据流：

*   代码生成临时的PCM音频数据，并赋值给Uint8Array变量audioData中。
*   AudioRenderer监听'writeData'回调，播放audioData音频流数据。

import { audio } from '@kit.AudioKit';
import { common } from '@kit.AbilityKit';
import { BusinessError } from '@kit.BasicServicesKit';

let audioRenderer: audio.AudioRenderer;
let audioStreamInfo: audio.AudioStreamInfo \= {
  samplingRate: audio.AudioSamplingRate.SAMPLE\_RATE\_8000, _// 采样率。_
  channels: audio.AudioChannel.CHANNEL\_1, _// 通道。_
  sampleFormat: audio.AudioSampleFormat.SAMPLE\_FORMAT\_S16LE, _// 采样格式。_
  encodingType: audio.AudioEncodingType.ENCODING\_TYPE\_RAW _//_ _编码格式。_
};
let audioRendererInfo: audio.AudioRendererInfo \= {
  usage: audio.StreamUsage.STREAM\_USAGE\_MUSIC, _// 音频流使用类型：音乐。根据业务场景配置，参考StreamUsage。_
  rendererFlags: 0 _// 音频渲染器标志。_
};
let audioRendererOptions: audio.AudioRendererOptions \= {
  streamInfo: audioStreamInfo,
  rendererInfo: audioRendererInfo
};

@Entry
@Component
export struct PlayPcmDataDemo {
  context \= this.getUIContext().getHostContext() as common.UIAbilityContext;
  audioData: Uint8Array \= generateTestPCM(); _// 测试PCM数据，按需替换为其他音频数据源_
  writeOffset \= 0;

  async aboutToAppear(): Promise<void\> {
    audioRenderer \= await audio.createAudioRenderer(audioRendererOptions);
    await this.init(); _//初始化_
  }

  async aboutToDisappear(): Promise<void\> {
    await audioRenderer.release();
  }

  build() {
    Column({ space: 10 }) {
      Button('播放音频数据')
        .width('100%')
        .onClick(async () \=\> {
          await audioRenderer.start();
        });
      Button('停止播放')
        .width('100%')
        .onClick(async () \=\> {
          console.info('renderer status' \+ audioRenderer.state);
          this.stopAndFlush();
        });
    }
    .padding(20)
    .justifyContent(FlexAlign.Center)
    .width('100%')
    .height('100%');
  }

  async init() {
    audioRenderer.on('writeData', (buffer: ArrayBuffer) \=\> {
      if (!this.audioData) {
        return audio.AudioDataCallbackResult.INVALID;
      }
      let bufferView \= new Uint8Array(buffer);
      let writeLen \= Math.min(buffer.byteLength, this.audioData.byteLength \- this.writeOffset);
      if (writeLen <\= 0) {
        this.writeOffset \= 0;
        console.info('Play Done');
        return audio.AudioDataCallbackResult.INVALID;
      }
      bufferView.set(this.audioData.slice(this.writeOffset, this.writeOffset \+ writeLen));
      this.writeOffset += writeLen;
      return audio.AudioDataCallbackResult.VALID;
    });
  }

  async stopAndFlush() {
    console.info('renderer status' \+ audioRenderer.state);
    audioRenderer.stop().then(() \=\> {
      console.error('Renderer stop ok.');
    }).catch((err: BusinessError) \=\> {
      console.error('Renderer stop failed. ', err);
    })
    ;
    audioRenderer.flush().then(() \=\> {
      console.error('Renderer flush ok.');
    }).catch((err: BusinessError) \=\> {
      console.error('renderer flush err. ' \+ err);
    });
    this.writeOffset \= 0;
  }
}

function generateTestPCM(): Uint8Array {
  const sampleRate \= 8000;
  const noteDuration \= 0.5;
  const amplitude \= 0.35;

  const freqMap: Record<number, number\> = {
    1: 523.25, _// C5_
    2: 587.33, _// D5_
    3: 659.25, _// E5_
    4: 698.46, _// F5_
    5: 783.99, _// G5_
    6: 880.00 _// A5_
  };

  const melody \= \[
    1, 1, 5, 5, 6, 6, 5, 0,
    4, 4, 3, 3, 2, 2, 1, 0,
    5, 5, 4, 4, 3, 3, 2, 0
  \];

  const samplesPerNote \= Math.floor(sampleRate \* noteDuration); _// 4000_
  const totalSamples \= samplesPerNote \* melody.length; _// 96,000_
  const buffer \= new ArrayBuffer(totalSamples \* 2); _// 192,000 bytes_
  const view \= new DataView(buffer);

  let idx \= 0;
  for (const note of melody) {
    const freq \= note ? freqMap\[note\] : 0;
    for (let i \= 0; i < samplesPerNote; i++) {
      const t \= i / sampleRate;
      const wave \= freq ? amplitude \* Math.sin(2 \* Math.PI \* freq \* t) : 0;
      const sample \= Math.round(wave \* 32767);
      const clamped \= Math.max(\-32768, Math.min(32767, sample));
      view.setInt16(idx \* 2, clamped, true);
      idx++;
    }
  }
  return new Uint8Array(buffer);
}