The two commonest sample rates are the awkward pair.

Every conversion between two sample rates is a fraction in lowest terms. The denominator is the cycle a resampler has to work in; the numerator is how many filter phases it needs. So 48 kHz to 96 reduces to 2/1 — a one-sample cycle, 64 coefficients. And 44,100 to 48,000 reduces to 160/147 — a 147-sample cycle and 5,120 coefficients, at the same filter length.

The engine is free and needs no account. Eighty times the table, and neither pair looks unusual written down. Nobody chose it either: 44,100 came from fitting digital audio onto video tape, 48,000 came from professional video, and the two worlds met. And if you do not convert — if the samples are handed to a device running another rate and nothing is interpolated — the material plays at the ratio of the rates: 44.1 kHz handed to 48 is +146.7 cents, nearly a semitone and a half sharp, and three minutes finishes in 2 min 45 s. Nothing in the file is wrong. The label is. Every lane ships a worked example that costs nothing. Writing the report needs credits.