audio-ui/lib/waveform/peaks.ts

/**
 * Waveform peak generation utilities
 */

/**
 * Generate waveform peaks from an AudioBuffer
 */
export function generatePeaks(
  audioBuffer: AudioBuffer,
  width: number,
  channelIndex: number = 0
): Float32Array {
  const channelData = audioBuffer.getChannelData(channelIndex);
  const peaks = new Float32Array(width);
  const samplesPerPeak = Math.floor(channelData.length / width);

  for (let i = 0; i < width; i++) {
    const start = i * samplesPerPeak;
    const end = Math.min(start + samplesPerPeak, channelData.length);

    let max = 0;
    for (let j = start; j < end; j++) {
      const abs = Math.abs(channelData[j]);
      if (abs > max) {
        max = abs;
      }
    }

    peaks[i] = max;
  }

  return peaks;
}

/**
 * Generate peaks for all channels
 */
export function generateMultiChannelPeaks(
  audioBuffer: AudioBuffer,
  width: number
): Float32Array[] {
  const peaks: Float32Array[] = [];

  for (let i = 0; i < audioBuffer.numberOfChannels; i++) {
    peaks.push(generatePeaks(audioBuffer, width, i));
  }

  return peaks;
}

/**
 * Generate min/max peaks for more detailed waveform visualization
 */
export function generateMinMaxPeaks(
  audioBuffer: AudioBuffer,
  width: number,
  channelIndex: number = 0
): { min: Float32Array; max: Float32Array } {
  const channelData = audioBuffer.getChannelData(channelIndex);
  const min = new Float32Array(width);
  const max = new Float32Array(width);
  const samplesPerPeak = Math.floor(channelData.length / width);

  for (let i = 0; i < width; i++) {
    const start = i * samplesPerPeak;
    const end = Math.min(start + samplesPerPeak, channelData.length);

    let minVal = 1;
    let maxVal = -1;

    for (let j = start; j < end; j++) {
      const val = channelData[j];
      if (val < minVal) minVal = val;
      if (val > maxVal) maxVal = val;
    }

    min[i] = minVal;
    max[i] = maxVal;
  }

  return { min, max };
}

/**
 * Normalize peaks to a given range
 */
export function normalizePeaks(peaks: Float32Array, targetMax: number = 1): Float32Array {
  const normalized = new Float32Array(peaks.length);
  let max = 0;

  // Find max value
  for (let i = 0; i < peaks.length; i++) {
    if (peaks[i] > max) {
      max = peaks[i];
    }
  }

  // Normalize
  const scale = max > 0 ? targetMax / max : 1;
  for (let i = 0; i < peaks.length; i++) {
    normalized[i] = peaks[i] * scale;
  }

  return normalized;
}