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/*
* @(#)Main.java
* Copyright © 2023 Werner Randelshofer, Switzerland. MIT License.
*/
package org.monte.media.anim;
import org.monte.media.math.Rational;
import javax.sound.sampled.AudioFormat;
import javax.sound.sampled.AudioInputStream;
import javax.sound.sampled.AudioSystem;
import java.io.IOException;
import java.util.Arrays;
/**
* Mixes multiple audio tracks into a single 16-bit PCM stereo audio track.
*/
public class AudioMixer {
/**
* The data array holds the mixed audio track.
*
* The 16-bit samples are stored in 32-bit integers, so that the mixer
* can handle intermediate results which are too loud for play-back.
*
* Two data elements represent one stereo audio sample.
*
* A data element at an even index contains an audio samples for the
* left channel.
* A data element at an odd index contains audio samples for the right
* channel.
*/
private int[] data = new int[0];
private final static AudioFormat stereoFormat = new AudioFormat(
44100,
16,
2, true, true);
private final static AudioFormat monoFormat = new AudioFormat(
44100,
16,
1, true, true);
/**
* Adds the provided audio samples to the audio track of the mixer.
*
* @param in the audio samples to be added
* @param startTime the start time in seconds at which the audio samples
* are to be added to the audio track
* @param repeats the number of repeats
* @param volume the desired audio volume.
* The valid range of values is 0.0 to Float.MAX_VALUE.
* @param pan the desired stereo pan (or balance).
* Supported values are -1: left only, 0: left and right,
*/
public void add(AudioInputStream in, Rational startTime, int repeats, float volume, int pan) throws IOException {
if (!(volume >= 0f && !Float.isNaN(volume))) {
throw new IllegalArgumentException("volume: " + volume);
}
float leftVolume, rightVolume;
switch (pan) {
case -1:
leftVolume = volume;
rightVolume = 0;
mixMono(in, startTime, repeats, leftVolume, rightVolume);
break;
case 0:
leftVolume = rightVolume = volume;
mixStereo(in, startTime, repeats, leftVolume, rightVolume);
break;
case 1:
leftVolume = 0;
rightVolume = 1;
mixMono(in, startTime, repeats, leftVolume, rightVolume);
break;
default:
throw new IllegalArgumentException("pan: " + pan);
}
}
private final byte[] tmp = new byte[1024];
public int getSampleCount() {
return data.length / 2;
}
private void mixMono(AudioInputStream in, Rational startTime, int repeats, float leftVolume, float rightVolume) throws IOException {
int destOffset = (int) startTime.floorNumerator((int) monoFormat.getSampleRate());
try (AudioInputStream converted = AudioSystem.getAudioInputStream(monoFormat, in)) {
converted.mark(Integer.MAX_VALUE);
for (int r = 0; r < repeats; r++) {
for (int count = converted.read(tmp); count != -1; count = converted.read(tmp)) {
mixMono(tmp, 0, count, destOffset, leftVolume, rightVolume);
destOffset += count / 2;
}
converted.reset();
}
}
}
private void mixMono(byte[] bytes, int off, int len, int destOffset, float leftVolume, float rightVolume) {
int j = destOffset * 2;
ensureCapacity(destOffset + len / 2);
for (int i = 0; i < len; i += 2) {
short inMono = (short) (((bytes[off + i] & 0xff) << 8) | ((bytes[off + i + 1] & 0xff) << 0));
int outLeft = (int) (inMono * leftVolume);
int outRight = (int) (inMono * rightVolume);
data[j++] += outLeft;
data[j++] += outRight;
}
}
/**
* Ensures capacity for the specified number of stereo samples.
*/
private void ensureCapacity(int size) {
if (data.length < size * 2) {
data = Arrays.copyOf(data, size * 2);
}
}
private void mixStereo(AudioInputStream in, Rational startTime, int repeats, float leftVolume, float rightVolume) throws IOException {
int destOffset = (int) startTime.floorNumerator((int) monoFormat.getSampleRate());
try (AudioInputStream converted = AudioSystem.getAudioInputStream(stereoFormat, in)) {
converted.mark(Integer.MAX_VALUE);
for (int r = 0; r < repeats; r++) {
for (int count = converted.read(tmp); count != -1; count = converted.read(tmp)) {
mixStereo(tmp, 0, count, destOffset, leftVolume, rightVolume);
destOffset += count / 4;
}
in.reset();
}
}
}
private void mixStereo(byte[] bytes, int off, int len, int destOffset, float leftVolume, float rightVolume) {
int j = destOffset * 2;
ensureCapacity(destOffset + len / 4);
for (int i = 0; i < len; i += 4) {
short inLeft = (short) (((bytes[off + i] & 0xff) << 8) | ((bytes[off + i + 1] & 0xff) << 0));
short inRight = (short) (((bytes[off + i + 2] & 0xff) << 8) | ((bytes[off + i + 3] & 0xff) << 0));
int outLeft = (int) (inLeft * leftVolume);
int outRight = (int) (inRight * rightVolume);
data[j++] += outLeft;
data[j++] += outRight;
}
}
public int getMaxAbsoluteValue() {
int maxAbs = 0;
for (int i = 0; i < data.length; i++) {
int abs = Math.abs(data[i]);
if (abs > maxAbs) {
maxAbs = abs;
}
}
return maxAbs;
}
public byte[] toByteArray() {
int maxAbs = getMaxAbsoluteValue();
byte[] b = new byte[getSampleCount() * 4];
if (maxAbs <= Short.MAX_VALUE) {
int j = 0;
for (int i = 0, n = data.length; i < n; i++) {
int sample = data[i];
b[j++] = (byte) ((sample & 0xff00) >> 8);
b[j++] = (byte) ((sample & 0xff));
}
} else {
float volume = Short.MAX_VALUE / (float) maxAbs;
int j = 0;
for (int i = 0, n = data.length; i < n; i++) {
int sample = (int) (data[i] * volume);
b[j++] = (byte) ((sample & 0xff00) >> 8);
b[j++] = (byte) ((sample & 0xff));
}
}
return b;
}
}