SonixEncoder

Encode raw PCM audio to compressed formats (M4A/AAC or MP3) for storage and sharing.

Quick Start

Kotlin

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

Swift

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

Encoding Methods

From AudioRawData

SonixEncoder.encode(
    data = audioRawData,
    outputPath = "/path/to/output.m4a",
    format = "m4a",         // "m4a" (default) or "mp3"
    bitrateKbps = 128       // default: 128
)

SonixEncoder.encode(
    data: audioRawData,
    outputPath: "/path/to/output.m4a",
    format: "m4a",
    bitrateKbps: 128
)

From Float Samples

Kotlin

SonixEncoder.encode(
    samples = floatArray,      // [-1.0, 1.0] range
    sampleRate = 44100,
    channels = 1,
    outputPath = "/path/to/output.m4a",
    format = "m4a",
    bitrateKbps = 128
)

Swift

SonixEncoder.encode(
    samples: floatArray,
    sampleRate: 44100,
    channels: 1,
    outputPath: "/path/to/output.m4a",
    format: "m4a",
    bitrateKbps: 128
)

From PCM Bytes

Kotlin

SonixEncoder.encode(
    pcmData = byteArray,       // 16-bit signed, little-endian
    sampleRate = 44100,
    channels = 1,
    outputPath = "/path/to/output.mp3",
    format = "mp3",
    bitrateKbps = 192
)

Swift

SonixEncoder.encode(
    pcmData: data,
    sampleRate: 44100,
    channels: 1,
    outputPath: "/path/to/output.mp3",
    format: "mp3",
    bitrateKbps: 192
)

Method Summary

Method	Input Type	Parameters
encode	AudioRawData	data, outputPath, format, bitrateKbps
encode	FloatArray / [Float]	samples, sampleRate, channels, outputPath, format, bitrateKbps
encode	ByteArray / Data	pcmData, sampleRate, channels, outputPath, format, bitrateKbps
isFormatAvailable	—	format: String → Boolean

Format Availability

if (SonixEncoder.isFormatAvailable("mp3")) {
    // MP3 encoding is supported on this platform
}

Supported Formats

Format	String	Quality	Use Case
M4A/AAC	"m4a" or "aac"	Best	Default choice, native hardware encoding
MP3	"mp3"	Good	Universal 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

Common Patterns

Convert Audio Format

// Decode MP3, re-encode as M4A
val audioData = SonixDecoder.decode("input.mp3", targetSampleRate = null)
if (audioData != null) {
    SonixEncoder.encode(data = audioData, outputPath = "output.m4a")
}

Export Synthesized Audio

val synth = SonixMidiSynthesizer.create(soundFontPath = sfPath)
synth.synthesizeFromNotes(notes, outputPath = "output.wav")

// Convert WAV to compressed MP3
val wavData = SonixDecoder.decode("output.wav", targetSampleRate = null)
if (wavData != null) {
    SonixEncoder.encode(data = wavData, outputPath = "output.mp3", format = "mp3")
}

Next Steps

• SonixDecoder — Decode audio files to raw PCM
• SonixRecorder — Record with automatic encoding
• SonixResampler — Resample before encoding