1 files changed, 95 insertions, 0 deletions
diff --git a/apps/web/src/fps/utils.ts b/apps/web/src/fps/utils.ts
new file mode 100644
index 00000000..e30e263a
--- /dev/null
+++ b/apps/web/src/fps/utils.ts
@@ -0,0 +1,95 @@
+import type { FrameRate } from "opencut-wasm";
+import type { MediaAsset } from "@/media/types";
+
+type MediaAssetFpsInput = Pick<MediaAsset, "type" | "fps">;
+
+const STANDARD_FRAME_RATES: Array<{ value: number; rate: FrameRate }> = [
+	{ value: 24_000 / 1_001, rate: { numerator: 24_000, denominator: 1_001 } },
+	{ value: 24, rate: { numerator: 24, denominator: 1 } },
+	{ value: 25, rate: { numerator: 25, denominator: 1 } },
+	{ value: 30_000 / 1_001, rate: { numerator: 30_000, denominator: 1_001 } },
+	{ value: 30, rate: { numerator: 30, denominator: 1 } },
+	{ value: 48, rate: { numerator: 48, denominator: 1 } },
+	{ value: 50, rate: { numerator: 50, denominator: 1 } },
+	{ value: 60_000 / 1_001, rate: { numerator: 60_000, denominator: 1_001 } },
+	{ value: 60, rate: { numerator: 60, denominator: 1 } },
+	{ value: 120, rate: { numerator: 120, denominator: 1 } },
+];
+
+const STANDARD_FRAME_RATE_TOLERANCE = 0.01;
+
+export function frameRateToFloat(rate: FrameRate): number {
+	return rate.numerator / rate.denominator;
+}
+
+export function frameRatesEqual(a: FrameRate, b: FrameRate): boolean {
+	return a.numerator === b.numerator && a.denominator === b.denominator;
+}
+
+export function floatToFrameRate(fps: number): FrameRate {
+	const standard = STANDARD_FRAME_RATES.find(
+		(candidate) => Math.abs(fps - candidate.value) <= STANDARD_FRAME_RATE_TOLERANCE,
+	);
+	if (standard) return standard.rate;
+
+	if (Number.isInteger(fps)) {
+		return { numerator: fps, denominator: 1 };
+	}
+
+	const ARBITRARY_DENOMINATOR = 1_000_000;
+	const scaledNumerator = Math.round(fps * ARBITRARY_DENOMINATOR);
+	const divisor = gcd(scaledNumerator, ARBITRARY_DENOMINATOR);
+	return {
+		numerator: scaledNumerator / divisor,
+		denominator: ARBITRARY_DENOMINATOR / divisor,
+	};
+}
+
+function gcd(left: number, right: number): number {
+	let a = Math.abs(left);
+	let b = Math.abs(right);
+	while (b !== 0) {
+		const remainder = a % b;
+		a = b;
+		b = remainder;
+	}
+	return a || 1;
+}
+
+export function getHighestImportedVideoFps({
+	mediaAssets,
+}: {
+	mediaAssets: MediaAssetFpsInput[];
+}): number | null {
+	let highestFps: number | null = null;
+
+	for (const asset of mediaAssets) {
+		const fps = asset.fps ?? Number.NaN;
+		if (asset.type !== "video") continue;
+		if (!Number.isFinite(fps) || fps <= 0) continue;
+
+		highestFps = highestFps === null ? fps : Math.max(highestFps, fps);
+	}
+
+	return highestFps;
+}
+
+export function getRaisedProjectFpsForImportedMedia({
+	currentFps,
+	importedAssets,
+}: {
+	currentFps: FrameRate;
+	importedAssets: MediaAssetFpsInput[];
+}): FrameRate | null {
+	const highestImportedVideoFps = getHighestImportedVideoFps({
+		mediaAssets: importedAssets,
+	});
+
+	const currentFpsFloat = frameRateToFloat(currentFps);
+
+	if (highestImportedVideoFps === null || highestImportedVideoFps <= currentFpsFloat) {
+		return null;
+	}
+
+	return floatToFrameRate(highestImportedVideoFps);
+}