tav-media/lib/src/wasm/audio-worklet/movie-audio-processor.js

Cross platform media editing framework

export const movieAudioProcessorCode = `class MovieAudioProcessor extends AudioWorkletProcessor {
  static get parameterDescriptors() {
    return [
      { name: 'bitDepth', defaultValue: 16, minValue: 1, maxValue: 32 },
    ];
  }

  constructor() {
    super();
    this.bitDepth_ = 16;
    this.paused = false;
    this.inputIndexes = [];
    this.port.onmessage = (e) => {
      const { operation, index } = e.data;
      if (operation === 'pause') {
        this.paused = true;
      } else if (operation === 'play') {
        this.paused = false;
      } else if (operation === 'connect') {
        this.inputIndexes.push(index);
      } else if (operation === 'disconnect') {
        this.inputIndexes.splice(this.inputIndexes.indexOf(index), 1);
      }
    }
  }

  handleMessage() {
    this.port.postMessage('received');
  }

  process(inputs, outputs, parameters) {
    if (this.paused) return true;
    if (inputs.length === 0) {
      return true;
    }

    const { bitDepth } = parameters;
    const factor = 2 ** (bitDepth - 1);
    const range = 25000;

    const outBuffers = [];
    const outDataList = {};
    for (const inputIndex of this.inputIndexes) {
      const input = inputs[inputIndex];
      if (!input || input.length === 0) {
        continue;
      };
      const sampleCount = input[0].length;
      const outData = [];
      for (let channel = 0; channel < input.length; ++channel) {
        for (let dataIndex = 0; dataIndex < input[channel].length; dataIndex++) {
          let transformedValue = Math.floor(input[channel][dataIndex] * factor + 0.5);
          if (transformedValue >= range ) {
            transformedValue = range;
          } else
            if (transformedValue <= -range) {
              transformedValue = -range;
            }
          outData[input.length * dataIndex + channel] = transformedValue;
        }
      }
      const arrayBuffer = new Int16Array(outData);
      outDataList[inputIndex] = {
        bytes: arrayBuffer.buffer,
        sampleCount,
        channelCount: input.length,
      };
      outBuffers.push(arrayBuffer.buffer);
    }

    this.port.postMessage({
      outDataList
    }, outBuffers);

    return true;
  }
}
registerProcessor('movie-audio-processor', MovieAudioProcessor);`;