audio-ui/lib/audio/effects/normalize.ts

/**
 * Normalization effects
 */

import { getAudioContext } from '../context';

/**
 * Normalize audio to peak amplitude
 * @param buffer - Source audio buffer
 * @param targetPeak - Target peak amplitude (0.0 to 1.0, default 1.0)
 * @returns New audio buffer with normalized audio
 */
export function normalizePeak(buffer: AudioBuffer, targetPeak: number = 1.0): AudioBuffer {
  const audioContext = getAudioContext();

  // Find the absolute peak across all channels
  let maxPeak = 0;
  for (let channel = 0; channel < buffer.numberOfChannels; channel++) {
    const channelData = buffer.getChannelData(channel);
    for (let i = 0; i < buffer.length; i++) {
      const abs = Math.abs(channelData[i]);
      if (abs > maxPeak) {
        maxPeak = abs;
      }
    }
  }

  // Calculate gain factor
  const gainFactor = maxPeak > 0 ? targetPeak / maxPeak : 1.0;

  // Create output buffer and apply gain
  const outputBuffer = audioContext.createBuffer(
    buffer.numberOfChannels,
    buffer.length,
    buffer.sampleRate
  );

  for (let channel = 0; channel < buffer.numberOfChannels; channel++) {
    const inputData = buffer.getChannelData(channel);
    const outputData = outputBuffer.getChannelData(channel);

    for (let i = 0; i < buffer.length; i++) {
      outputData[i] = inputData[i] * gainFactor;
    }
  }

  return outputBuffer;
}

/**
 * Normalize audio to RMS (loudness)
 * @param buffer - Source audio buffer
 * @param targetRMS - Target RMS level (0.0 to 1.0, default 0.5)
 * @returns New audio buffer with normalized audio
 */
export function normalizeRMS(buffer: AudioBuffer, targetRMS: number = 0.5): AudioBuffer {
  const audioContext = getAudioContext();

  // Calculate RMS across all channels
  let sumSquares = 0;
  let totalSamples = 0;

  for (let channel = 0; channel < buffer.numberOfChannels; channel++) {
    const channelData = buffer.getChannelData(channel);
    for (let i = 0; i < buffer.length; i++) {
      sumSquares += channelData[i] * channelData[i];
      totalSamples++;
    }
  }

  const currentRMS = Math.sqrt(sumSquares / totalSamples);
  const gainFactor = currentRMS > 0 ? targetRMS / currentRMS : 1.0;

  // Create output buffer and apply gain
  const outputBuffer = audioContext.createBuffer(
    buffer.numberOfChannels,
    buffer.length,
    buffer.sampleRate
  );

  for (let channel = 0; channel < buffer.numberOfChannels; channel++) {
    const inputData = buffer.getChannelData(channel);
    const outputData = outputBuffer.getChannelData(channel);

    for (let i = 0; i < buffer.length; i++) {
      outputData[i] = inputData[i] * gainFactor;
      // Clamp to prevent distortion
      outputData[i] = Math.max(-1, Math.min(1, outputData[i]));
    }
  }

  return outputBuffer;
}

/**
 * Get peak amplitude of audio buffer
 * @param buffer - Audio buffer
 * @returns Peak amplitude (0.0 to 1.0)
 */
export function getPeakAmplitude(buffer: AudioBuffer): number {
  let maxPeak = 0;
  for (let channel = 0; channel < buffer.numberOfChannels; channel++) {
    const channelData = buffer.getChannelData(channel);
    for (let i = 0; i < buffer.length; i++) {
      const abs = Math.abs(channelData[i]);
      if (abs > maxPeak) {
        maxPeak = abs;
      }
    }
  }
  return maxPeak;
}

/**
 * Get RMS amplitude of audio buffer
 * @param buffer - Audio buffer
 * @returns RMS amplitude
 */
export function getRMSAmplitude(buffer: AudioBuffer): number {
  let sumSquares = 0;
  let totalSamples = 0;

  for (let channel = 0; channel < buffer.numberOfChannels; channel++) {
    const channelData = buffer.getChannelData(channel);
    for (let i = 0; i < buffer.length; i++) {
      sumSquares += channelData[i] * channelData[i];
      totalSamples++;
    }
  }

  return Math.sqrt(sumSquares / totalSamples);
}