Frame rates and exact time conversion

Use these rules when converting between video frames, editorial time and audio samples. For ordinary panel timing, start with animation.

Exact tick conversionCopy Anchor Link

normalizeRate(23.976) returns {numerator:2997, denominator:125}. It preserves the decimal value; it does not infer 24000/1001. Supply that fraction explicitly when required.

import { normalizeRate, rescaleTime } from 'codeboard-studio';
const fps = normalizeRate({ numerator: 24000, denominator: 1001 });
const sample = rescaleTime(24, fps, 48000, 'exact');
// sample.value is 48048; sample.exact is true.

rescaleTime(position, sourceRate, targetRate, rounding) converts integer ticks between positive rates. Rates accept positive finite numbers or safe-integer numerator/denominator objects. Intermediate arithmetic uses BigInt; returned positions must fit a safe integer. Policies are nearest (default, ties toward positive infinity), floor, ceil, and exact (rejects quantization). error contains reduced integer strings describing rounded minus exact destination position. Negative tick positions support studio preroll; board authoring methods retain their nonnegative frame rules.

Project preserve-seconds retiming reuses this mapper and retains collision/collapsed-interval rejection. Project board timelines still store a numeric rate and global frames. Board rates remain numeric; studio animations and editorial sequences persist their own rational rates.