Samplerateconversion

Samplerateconversion is the process of converting a discrete-time signal from one sampling rate to another. It is common in audio, multimedia, and communications to enable mixing sources with different rates, standardize to a target rate, or match hardware constraints. The operation aims to preserve spectral content within the new bandwidth while minimizing aliasing and distortion.

The standard approach involves upsampling by a factor L (inserting L−1 zeros between samples) and applying a low-pass reconstruction filter, followed by downsampling by a factor M (keeping every M-th sample). For arbitrary rate changes, techniques use polyphase finite impulse response filters or FFT-based resampling. The ideal reconstruction uses a sinc interpolation, but it requires an infinite impulse response; practical implementations use finite filters to approximate it.

Time-domain methods include zero-order hold, linear or higher-order interpolation, and spline approaches. These are simple and fast but can introduce distortion or imaging at the output rate. Frequency-domain methods resample by reshaping the spectrum with a band-limited filter and reassembling samples at the target rate. Windowed sinc and polyphase designs are common in real-time resamplers.

Key considerations include anti-aliasing, imaging suppression, phase accuracy, latency, and numerical precision. The preferred method balances quality, speed, and resource use. In practice, many software and hardware resamplers offer configurable quality settings.

Samplerate conversion is essential in audio production, streaming, and digital communications to ensure compatibility between devices and systems at different sampling rates.