SonixResampler

High-quality audio resampling using libsamplerate.

What is Resampling?

Audio is recorded at a specific sample rate (samples per second). Different systems use different rates:

• CD quality: 44100 Hz

• Video: 48000 Hz

• Calibra APIs: 16000 Hz

Resampling converts audio between sample rates while preserving audio quality.

When to Use

Quick Start

Kotlin

// Resample from 44100 Hz to 16000 Hz (for Calibra)
val resampled = SonixResampler.resample(
    samples = audioSamples,
    fromRate = 44100,
    toRate = 16000
)

// Now use with Calibra
val contour = pitchExtractor.extract(resampled, 16000)

Swift

// Resample from 44100 Hz to 16000 Hz (for Calibra)
let resampled = SonixResampler.resample(
    samples: audioSamples,
    fromRate: 44100,
    toRate: 16000
)

// Now use with Calibra
let contour = pitchExtractor.extract(audio: resampled, sampleRate: 16000)

Quality

Uses libsamplerate (Secret Rabbit Code) which provides:

• High-quality sinc interpolation

• Minimal aliasing artifacts

• Fast performance on mobile devices

Platform Notes

iOS/Android

• Uses native libsamplerate library (compiled for each platform)

• Processing time scales with audio length and rate ratio

Common Pitfalls

1. Mono only: Input must be mono; convert stereo to mono first

2. Memory usage: Creates new array for output (doesn't modify input)

3. Usually unnecessary: SonixDecoder.decode() already resamples to 16kHz

See also