VoxaTrace/com.musicmuni.voxatrace.sonix/SonixEncoder

SonixEncoder

Encodes audio to compressed formats (M4A/AAC, MP3).

What is Audio Encoding?

Raw PCM audio uses a lot of space (~10MB per minute at 44kHz stereo). Encoding compresses audio to efficient formats like M4A or MP3 for storage and sharing.

Use it when you need to:

Save recorded audio to a file
Export synthesized audio
Convert between audio formats

When to Use

Scenario	Use This?	Why
Save recording to file	Yes	Core use case
Export synthesized audio	Yes	After synthesis
Convert audio formats	Yes	Decode + encode
Record audio directly	No	Use `SonixRecorder` (encodes internally)

Quick Start

Kotlin

// Encode from AudioRawData (e.g., after decoding or synthesis)
val rawData = SonixDecoder.decode("input.wav")
if (rawData != null) {
    val success = SonixEncoder.encode(
        data = rawData,
        outputPath = "/path/to/output.mp3",
        format = "mp3"
    )
}

// Encode from float samples
val success = SonixEncoder.encode(
    samples = floatArray,
    sampleRate = 44100,
    channels = 1,
    outputPath = "/path/to/output.m4a"
)

// Check format availability
if (SonixEncoder.isFormatAvailable("mp3")) {
    // MP3 encoding is supported
}

Swift

// Encode from AudioRawData
if let rawData = SonixDecoder.decode(path: "input.wav", targetSampleRate: nil) {
    let success = SonixEncoder.encode(
        data: rawData,
        outputPath: "/path/to/output.mp3",
        format: "mp3",
        bitrateKbps: 128
    )
}

// Encode from float samples
let success = SonixEncoder.encode(
    samples: floatArray,
    sampleRate: 44100,
    channels: 1,
    outputPath: "/path/to/output.m4a",
    format: "m4a",
    bitrateKbps: 128
)

Supported Formats

Format	Quality	Compatibility	Use Case
M4A/AAC	Best	iOS/Android native	Default choice
MP3	Good	Universal	Maximum compatibility

Bitrate Guide

Bitrate	Quality	File Size
64 kbps	Low (voice)	~0.5 MB/min
128 kbps	Standard	~1 MB/min
192 kbps	High	~1.5 MB/min
256 kbps	Very high	~2 MB/min

Platform Notes

iOS

M4A/AAC uses AVFoundation (hardware accelerated)
MP3 uses LAME library

Android

M4A/AAC uses MediaCodec (hardware accelerated)
MP3 uses LAME library

Common Pitfalls

False return: Encoding failed - check file permissions and path validity
Large memory usage: Encoding processes entire audio in memory
Wrong sample format: Float samples must be in -1.0, 1.0 range
Blocking call: Runs synchronously; consider calling from background thread

Functions

encode

fun encode(data: AudioRawData, outputPath: String, format: String = "m4a", bitrateKbps: Int = 128): Boolean

Encode AudioRawData to a compressed audio file.

fun encode(pcmData: ByteArray, sampleRate: Int, channels: Int, outputPath: String, format: String = "m4a", bitrateKbps: Int = 128): Boolean

Encode PCM bytes to a compressed audio file.

fun encode(samples: FloatArray, sampleRate: Int, channels: Int, outputPath: String, format: String = "m4a", bitrateKbps: Int = 128): Boolean

Encode float samples to a compressed audio file.

isFormatAvailable

fun isFormatAvailable(format: String): Boolean

Check if a format is available on this platform.