Share My Creation B4A Audio Equalizer

Full Explanation of the Audio Equalizer + BassBoost + Virtualizer + Presets + Visualizer (B4XPages + ExoPlayer)​

This code implements a complete audio processing page using B4XPages. It includes:

• SimpleExoPlayer audio playback
• Android AudioFX Equalizer (5 bands)
• BassBoost
• Virtualizer
• Preset system (Pop, Rock, Techno, Vocal Booster, etc.)
• Winamp‑style visualizer simulation
• Automatic persistence using KeyValueStore
• Dynamic initialization based on the audio session ID

It is designed to be easy to integrate, modify, and extend.

1. Page Initialization​

In B4XPage_Created, the code:

• loads the layout
• initializes KeyValueStore
• configures the ComboBox
• groups the 5 equalizer sliders into a list
• assigns each slider a Tag representing its band index
• initializes the visualizer arrays
• starts a timer for the visualizer (≈30 FPS)
• initializes ExoPlayer and prepares a sample MP3

This creates the foundation for the equalizer and visualizer.

2. Dynamic Equalizer Initialization​

Android’s audio effects (Equalizer, BassBoost, Virtualizer) must be created using the audio session ID of the player.

When ExoPlayer is ready:

Dim AudioSessionId As Int = nativePlayer.RunMethod("getAudioSessionId", Null)

If the ID is valid, the code initializes:

EQ.InitializeNewInstance("android.media.audiofx.Equalizer", Array(0, SessionId))
BassBoost.InitializeNewInstance("android.media.audiofx.BassBoost", Array(0, SessionId))
Virtualizer.InitializeNewInstance("android.media.audiofx.Virtualizer", Array(0, SessionId))

Then:

• retrieves the min/max band levels
• configures each slider’s range
• restores saved values from KeyValueStore
• applies the saved equalizer settings

This ensures the equalizer is fully synchronized with the audio engine.

3. Equalizer Sliders​

Each equalizer slider has a Tag containing its band index.

When a slider changes:

Dim BandIndex As Int = sb.Tag
Dim TargetMilliBels As Short = Value + EQMinLevel
EQ.RunMethod("setBandLevel", Array(AsShort(BandIndex), TargetMilliBels))

The value is also saved:

kvs.Put("Band_" & BandIndex, Value)

This makes the equalizer responsive and persistent.

BassBoost & Virtualizer​

These effects use the same pattern:

BassBoost.RunMethod("setStrength", Array(AsShort(Value)))
Virtualizer.RunMethod("setStrength", Array(AsShort(Value)))

Both values are saved in KeyValueStore.

5. Preset System​

The ComboBox contains several audio profiles:

• Flat
• Pop
• Rock
• Techno / Dance
• Vocal Booster

Each preset defines:

• 5 equalizer band values
• BassBoost strength
• Virtualizer strength

The preset is applied using:

EQ.RunMethod("setBandLevel", Array(AsShort(i), AsShort(GainMilliBels)))
sb.Value = SliderValue

This updates both the audio engine and the UI.

6. Winamp‑Style Visualizer​

The visualizer is a simulation, not a real FFT. It uses:

• 32 bars
• random values influenced by equalizer energy
• peak‑hold effect
• decay over time
• a timer running at ~30 FPS

Each timer tick:

1. Updates bar values
2. Updates peak values
3. Draws bars and peaks on a B4XCanvas
4. Clears and redraws the panel

This produces a smooth, animated visualizer similar to classic Winamp skins.

7. Automatic Persistence (KeyValueStore)
All user settings are saved:

• equalizer band levels
• BassBoost strength
• Virtualizer strength

On startup, the values are restored and applied automatically.
This makes the audio page behave like a real equalizer app.

8. Summary for B4X Developers​

This code demonstrates:

• how to use ExoPlayer with B4XPages
• how to initialize Android AudioFX correctly
• how to build a multi‑band equalizer
• how to implement BassBoost and Virtualizer
• how to create a preset system
• how to draw a custom visualizer
• how to persist settings with KeyValueStore

It can be used as:

• a base for a full audio player
• a learning example for AudioFX
• a visualizer demo
• an equalizer module for existing apps

Required libraries

Have fun