Audio Sample Rate Converter

How to Convert Audio Sample Rates Online

Why Sample Rate Mismatch Causes Audio-Video Drift in Video Editors

One of the most persistent headaches in video production occurs when an editor imports music tracks recorded at $44,100 ext{ Hz}$ into a timeline configured for $48,000 ext{ Hz}$ video standard. Over a 30-minute documentary or podcast interview, dialogue slowly slips out of synchronization by several frames, causing lip-sync mismatch.

This happens because video frames divide evenly into 48,000 samples per second ($48,000 / 24 = 2,000 ext{ samples/frame}$; $48,000 / 30 = 1,600 ext{ samples/frame}$), whereas $44,100$ produces fractional samples ($44,100 / 24 = 1,837.5 ext{ samples/frame}$). Over time, rounding errors accumulate into noticeable drift.

The Mathematics of Sinc Interpolation and Anti-Aliasing

Sample rate conversion is not simply dropping or duplicating samples (which causes severe harmonic distortion and ringing). High-quality resampling reconstructs the continuous analog curve using the Whittaker-Shannon interpolation formula:

$$x(t) = sum_{n=-infty}^{infty} x[n] cdot ext{sinc}left(rac{t - nT}{T} ight) quad ext{where } ext{sinc}(u) = rac{sin(pi u)}{pi u}$$

When downsampling (e.g. from 96 kHz to 44.1 kHz), an aggressive steep low-pass brickwall filter is applied at $22,050 ext{ Hz}$ to prevent ultrasonic energy from folding over into audible frequencies as harsh aliasing noise.

Key Benefits of the Audio Sample Rate Converter

Frequently Asked Questions