Class AudioMixer

java.lang.Object
com.codename1.media.AudioMixer
public class AudioMixer extends Object

Mixes multiple PCM tracks into a single AudioBuffer.

AudioMixer is a platform-neutral helper for building a sample-accurate PCM timeline. All tracks are locked to the mixer sample rate and channel count. Track offsets are converted to sample frames on that clock, and the mixed output uses interleaved float PCM samples in the same format as AudioBuffer and WAVWriter.

AudioMixer mixer = new AudioMixer(44100, 2);
mixer.addTrack(musicBuffer, 0, 0.5f);
mixer.addTrack(effectBuffer, 250, 1.0f);
AudioBuffer mixed = mixer.mix();
float[] pcm = new float[mixed.getSize()];
mixed.copyTo(pcm);
wavWriter.write(pcm, 0, mixed.getSize());

  • Constructor Summary

    Constructors
    Constructor
    Description
    AudioMixer(int sampleRate, int numChannels)
    Creates a new mixer locked to a single sample clock.

  • Method Summary

    Modifier and Type
    Method
    Description
    AudioMixer
    addTrack(float[] pcmData, int offset, int len, long offsetMs, float gain)
    Adds an interleaved PCM track range at the given millisecond offset.
    AudioMixer
    addTrack(float[] pcmData, long offsetMs, float gain)
    Adds an interleaved PCM track at the given millisecond offset.
    AudioMixer
    addTrack(AudioBuffer source, long offsetMs, float gain)
    Adds an AudioBuffer track at the given millisecond offset.
    AudioMixer
    addTrackAtFrame(float[] pcmData, int offset, int len, int offsetFrame, float gain)
    Adds an interleaved PCM track range at an exact sample-frame offset.
    AudioMixer
    addTrackAtFrame(AudioBuffer source, int offsetFrame, float gain)
    Adds an AudioBuffer track at an exact sample-frame offset.
    void
    clear()
    Removes all tracks from this mixer.
    int
    getNumChannels()
    Gets the number of interleaved channels used by this mixer.
    int
    getOutputFrameCount()
    Gets the number of sample frames in the mixed output.
    int
    getOutputSize()
    Gets the number of interleaved samples in the mixed output.
    int
    getSampleRate()
    Gets the sample rate used by this mixer.
    int
    getTrackCount()
    Gets the number of tracks currently in the mixer.
    static boolean
    isSimdOptimizationsEnabled()
    Indicates whether the mixer should use SIMD-backed kernels when the current platform supports them.
    AudioBuffer
    mix()
    Mixes all tracks into a new AudioBuffer.
    static void
    resetSimdOptimizationsEnabled()
    Restores the default SIMD optimization setting for this platform.
    static void
    setSimdOptimizationsEnabled(boolean enabled)
    Enables or disables SIMD-backed mixer optimizations.

    Methods inherited from class Object

    clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Constructor Details

    • AudioMixer

      public AudioMixer(int sampleRate, int numChannels)

      Creates a new mixer locked to a single sample clock.

      Parameters
      • sampleRate: The sample rate in frames per second. E.g. 44100.
      • numChannels: The number of interleaved channels. E.g. 1 or 2.

  • Method Details

    • isSimdOptimizationsEnabled

      public static boolean isSimdOptimizationsEnabled()

      Indicates whether the mixer should use SIMD-backed kernels when the current platform supports them.

      Returns

      true when SIMD optimizations are enabled.

    • setSimdOptimizationsEnabled

      public static void setSimdOptimizationsEnabled(boolean enabled)

      Enables or disables SIMD-backed mixer optimizations.

      This only affects internal implementation choices; mixed samples and clipping semantics are unchanged.

      Parameters
      • enabled: true to use SIMD where supported, false to force scalar loops.

    • resetSimdOptimizationsEnabled

      public static void resetSimdOptimizationsEnabled()
      Restores the default SIMD optimization setting for this platform.

    • getSampleRate

      public int getSampleRate()

      Gets the sample rate used by this mixer.

      Returns

      the sample rate in frames per second.

    • getNumChannels

      public int getNumChannels()

      Gets the number of interleaved channels used by this mixer.

      Returns

      the number of channels.

    • getTrackCount

      public int getTrackCount()

      Gets the number of tracks currently in the mixer.

      Returns

      the number of tracks.

    • clear

      public void clear()
      Removes all tracks from this mixer.

    • addTrack

      public AudioMixer addTrack(AudioBuffer source, long offsetMs, float gain)

      Adds an AudioBuffer track at the given millisecond offset.

      The source samples are copied when the track is added so the source buffer can be reused or modified afterwards. The offset is rounded to the nearest sample frame on the mixer clock.

      Parameters
      • source: Source PCM buffer. Its sample rate and channel count must match the mixer.
      • offsetMs: Offset from the start of the timeline in milliseconds.
      • gain: Gain multiplier for this track. 1.0f preserves level.
      Returns

      this mixer.

    • addTrackAtFrame

      public AudioMixer addTrackAtFrame(AudioBuffer source, int offsetFrame, float gain)

      Adds an AudioBuffer track at an exact sample-frame offset.

      Use this method when the track position is already known in frames and no millisecond conversion should be applied.

      Parameters
      • source: Source PCM buffer. Its sample rate and channel count must match the mixer.
      • offsetFrame: Offset from the start of the timeline in sample frames.
      • gain: Gain multiplier for this track. 1.0f preserves level.
      Returns

      this mixer.

    • addTrack

      public AudioMixer addTrack(float[] pcmData, long offsetMs, float gain)

      Adds an interleaved PCM track at the given millisecond offset.

      The source samples are copied when the track is added. The offset is rounded to the nearest sample frame on the mixer clock.

      Parameters
      • pcmData: Interleaved PCM samples.
      • offsetMs: Offset from the start of the timeline in milliseconds.
      • gain: Gain multiplier for this track. 1.0f preserves level.
      Returns

      this mixer.

    • addTrack

      public AudioMixer addTrack(float[] pcmData, int offset, int len, long offsetMs, float gain)

      Adds an interleaved PCM track range at the given millisecond offset.

      The source samples are copied when the track is added. The offset is rounded to the nearest sample frame on the mixer clock.

      Parameters
      • pcmData: Interleaved PCM samples.
      • offset: Offset in pcmData to start copying from.
      • len: Number of samples to copy.
      • offsetMs: Offset from the start of the timeline in milliseconds.
      • gain: Gain multiplier for this track. 1.0f preserves level.
      Returns

      this mixer.

    • addTrackAtFrame

      public AudioMixer addTrackAtFrame(float[] pcmData, int offset, int len, int offsetFrame, float gain)

      Adds an interleaved PCM track range at an exact sample-frame offset.

      Parameters
      • pcmData: Interleaved PCM samples.
      • offset: Offset in pcmData to start copying from.
      • len: Number of samples to copy.
      • offsetFrame: Offset from the start of the timeline in sample frames.
      • gain: Gain multiplier for this track. 1.0f preserves level.
      Returns

      this mixer.

    • getOutputFrameCount

      public int getOutputFrameCount()

      Gets the number of sample frames in the mixed output.

      Returns

      the mixed timeline length in sample frames.

    • getOutputSize

      public int getOutputSize()

      Gets the number of interleaved samples in the mixed output.

      Returns

      the mixed timeline length in samples.

    • mix

      public AudioBuffer mix()

      Mixes all tracks into a new AudioBuffer.

      The output is clipped to the normalized PCM range [-1, 1] so it can be passed directly to WAVWriter.

      Returns

      a new AudioBuffer containing the mixed PCM timeline.