Load and Analyze PCM samples

load-and-analyze-samples.js

// Keep an array of indexes of loud samples.
const loud_indexes = [0];
{
  const pcm_data = fs.readFileSync(pcm_output, { encoding: null });
  const pcm_values = new Int16Array(pcm_data.buffer);

  // The first segment may be longer than normal due to Icecast
  // buffering.
  if (pcm_values.length > (window_length / 1000) * sample_rate * 1.2) {
      return;
  }

  pcm_values.forEach((v, idx) => {
      if (Math.abs(v) > loud_threshold) {
          loud_indexes.push(idx);
      }
  });
  loud_indexes.push(pcm_values.length - 1);
};

let total_silence_seconds = 0;

if (loud_indexes.length < 2) {
  total_silence_seconds = window_length / 1000;
}

// Loop over all of the indexes where a sample was louder
// then the threshold and determine the amount of time
// that the channel was silent, if its > .25 of a second
// count that duration of time as silence.
for (let i = 1; i < loud_indexes.length; i++) {
  const sample_dist = loud_indexes[i] - loud_indexes[i - 1];
  if (sample_dist > (sample_rate * .25)) {
      diff_indexes.push(sample_dist);
      total_silence_seconds += sample_dist / sample_rate;
  }
}