code: function blockHead_(sample) {
    encodeSample_(sample);
    /** @type {!Array<number>} */
    let adpcmSamples = [];
    adpcmSamples.push(sample & 0xFF);
    adpcmSamples.push((sample >> 8) & 0xFF);
    adpcmSamples.push(encoderIndex_);
    adpcmSamples.push(0);
    return adpcmSamples;
  }
docs: Return the head of a ADPCM sample block.
  @param {number} sample The first sample of the block.
  @return {!Array<number>}
  @private