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export const MEDIA_TILE_ASPECT_RATIO = 16 / 9;
export const FILMSTRIP_MIN_INTERVAL_SECONDS = 0.1;
export const FILMSTRIP_MAX_INTERVAL_SECONDS = 64;
export const FILMSTRIP_OVERSCAN_SLOTS = 2;
const SOURCE_TIME_END_PADDING_SECONDS = 0.05;
const TILE_TIME_QUANTUM_PER_SECOND = 4096;
export function getFilmstripInterval({
pixelsPerSecond,
minTileWidthPx,
}: {
pixelsPerSecond: number;
minTileWidthPx: number;
}): number {
if (
!Number.isFinite(pixelsPerSecond) ||
pixelsPerSecond <= 0 ||
!Number.isFinite(minTileWidthPx) ||
minTileWidthPx <= 0
) {
return FILMSTRIP_MAX_INTERVAL_SECONDS;
}
const ideal = minTileWidthPx / pixelsPerSecond;
const clamped = Math.min(
FILMSTRIP_MAX_INTERVAL_SECONDS,
Math.max(FILMSTRIP_MIN_INTERVAL_SECONDS, ideal),
);
return 2 ** Math.round(Math.log2(clamped));
}
export function getFilmstripSlotCount({
clipDurationSec,
interval,
}: {
clipDurationSec: number;
interval: number;
}): number {
if (
!Number.isFinite(clipDurationSec) ||
clipDurationSec <= 0 ||
interval <= 0
) {
return 0;
}
return Math.max(1, Math.ceil(clipDurationSec / interval - 1e-6));
}
export function getVisibleSlotRange({
slotCount,
tileWidthPx,
visibleLeftPx,
visibleRightPx,
overscanSlots = FILMSTRIP_OVERSCAN_SLOTS,
}: {
slotCount: number;
tileWidthPx: number;
visibleLeftPx: number;
visibleRightPx: number;
overscanSlots?: number;
}): { firstSlot: number; lastSlot: number } {
if (slotCount <= 0 || tileWidthPx <= 0 || visibleRightPx <= visibleLeftPx) {
return { firstSlot: 0, lastSlot: -1 };
}
const firstSlot = Math.max(
0,
Math.floor(visibleLeftPx / tileWidthPx) - overscanSlots,
);
const lastSlot = Math.min(
slotCount - 1,
Math.ceil(visibleRightPx / tileWidthPx) - 1 + overscanSlots,
);
return { firstSlot, lastSlot };
}
export function getFilmstripSlotSourceTime({
slot,
interval,
trimStartSec,
rate,
assetDurationSec,
}: {
slot: number;
interval: number;
trimStartSec: number;
rate: number;
assetDurationSec?: number;
}): number {
const safeRate = Number.isFinite(rate) && rate > 0 ? rate : 1;
const raw = Math.max(0, trimStartSec + slot * interval * safeRate);
if (
assetDurationSec === undefined ||
!Number.isFinite(assetDurationSec) ||
assetDurationSec <= 0
) {
return raw;
}
return Math.min(
raw,
Math.max(0, assetDurationSec - SOURCE_TIME_END_PADDING_SECONDS),
);
}
export function buildThumbnailTileKey({
mediaId,
time,
width,
height,
}: {
mediaId: string;
time: number;
width: number;
height: number;
}): string {
const quantizedTime = Math.round(
Math.max(0, time) * TILE_TIME_QUANTUM_PER_SECOND,
);
return `${mediaId}:${width}x${height}:${quantizedTime}`;
}
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