4 files changed, 52 insertions, 23 deletions
diff --git a/apps/web/src/timeline/components/drop-target.ts b/apps/web/src/timeline/components/drop-target.ts
index be2495e4..f68a4b72 100644
--- a/apps/web/src/timeline/components/drop-target.ts
+++ b/apps/web/src/timeline/components/drop-target.ts
@@ -3,7 +3,12 @@ import type { ComputeDropTargetParams, DropTarget } from "@/timeline";
 import { resolveTrackPlacement } from "@/timeline/placement";
 import { TIMELINE_TRACK_GAP_PX } from "./layout";
 import { getTrackHeight } from "./track-layout";
-import { TICKS_PER_SECOND } from "@/wasm";
+import {
+	mediaTime,
+	type MediaTime,
+	roundMediaTime,
+	TICKS_PER_SECOND,
+} from "@/wasm";
 
 function findElementAtPosition({
 	mouseX,
@@ -20,9 +25,11 @@ function findElementAtPosition({
 	pixelsPerSecond: number;
 	zoomLevel: number;
 }): { elementId: string; trackId: string } | null {
-	const time = Math.round(
-		(mouseX / (pixelsPerSecond * zoomLevel)) * TICKS_PER_SECOND,
-	);
+	const time = mediaTime({
+		ticks: Math.round(
+			(mouseX / (pixelsPerSecond * zoomLevel)) * TICKS_PER_SECOND,
+		),
+	});
 	const track = tracks[trackIndex];
 	if (!track || !("elements" in track)) return null;
 
@@ -82,7 +89,7 @@ const EMPTY_TARGET_ELEMENT = null;
 function fallbackNewTrackDropTarget({
 	xPosition,
 }: {
-	xPosition: number;
+	xPosition: MediaTime;
 }): DropTarget {
 	return {
 		trackIndex: 0,
@@ -111,13 +118,16 @@ export function computeDropTarget({
 	const orderedTracks = [...tracks.overlay, tracks.main, ...tracks.audio];
 	const mainTrackIndex = tracks.overlay.length;
 	const xPosition =
-		typeof startTimeOverride === "number"
+		startTimeOverride !== undefined
 			? startTimeOverride
 			: isExternalDrop
 				? playheadTime
-				: Math.round(
-				Math.max(0, mouseX / (pixelsPerSecond * zoomLevel)) * TICKS_PER_SECOND,
-			);
+				: mediaTime({
+						ticks: Math.round(
+							Math.max(0, mouseX / (pixelsPerSecond * zoomLevel)) *
+								TICKS_PER_SECOND,
+						),
+					});
 
 	if (orderedTracks.length === 0) {
 		const placementResult = resolveTrackPlacement({
@@ -221,7 +231,10 @@ export function computeDropTarget({
 	}
 
 	if (placementResult.kind === "existingTrack") {
-		const adjustedXPosition = placementResult.adjustedStartTime ?? xPosition;
+		const adjustedXPosition =
+			placementResult.adjustedStartTime !== undefined
+				? roundMediaTime({ time: placementResult.adjustedStartTime })
+				: xPosition;
 
 		return {
 			trackIndex: placementResult.trackIndex,
diff --git a/apps/web/src/timeline/components/index.tsx b/apps/web/src/timeline/components/index.tsx
index e6a9df49..5d61a0a9 100644
--- a/apps/web/src/timeline/components/index.tsx
+++ b/apps/web/src/timeline/components/index.tsx
@@ -29,6 +29,7 @@ import {
 	useState,
 	type ReactNode,
 } from "react";
+import type { MediaTime } from "@/wasm";
 import type { ElementDragState, DropTarget } from "@/timeline";
 import { TimelineTrackContent } from "./timeline-track";
 import { TimelinePlayhead } from "./timeline-playhead";
@@ -132,7 +133,7 @@ export function Timeline() {
 		[scene],
 	);
 	const mainTrackId = scene?.tracks.main.id ?? null;
-	const seek = (time: number) => editor.playback.seek({ time });
+	const seek = (time: MediaTime) => editor.playback.seek({ time });
 
 	const timelineRef = useRef<HTMLDivElement>(null);
 	const timelineHeaderRef = useRef<HTMLDivElement>(null);
diff --git a/apps/web/src/timeline/components/timeline-element.tsx b/apps/web/src/timeline/components/timeline-element.tsx
index 74c34607..e0eeb378 100644
--- a/apps/web/src/timeline/components/timeline-element.tsx
+++ b/apps/web/src/timeline/components/timeline-element.tsx
@@ -49,7 +49,7 @@ import {
 import { buildWaveformGainSamples } from "@/timeline/audio-state";
 import { getTimelinePixelsPerSecond } from "@/timeline";
 import { buildWaveformSourceKey } from "@/media/waveform-summary";
-import { TICKS_PER_SECOND } from "@/wasm/ticks";
+import { addMediaTime, TICKS_PER_SECOND, ZERO_MEDIA_TIME } from "@/wasm";
 import {
 	getActionDefinition,
 	type TAction,
@@ -257,10 +257,11 @@ export function TimelineElement({
 		isBeingDragged && dragState.isDragging
 			? dragState.currentMouseY - dragState.startMouseY
 			: 0;
-	const dragTimeOffset = dragState.dragTimeOffsets[element.id] ?? 0;
+	const dragTimeOffset =
+		dragState.dragTimeOffsets[element.id] ?? ZERO_MEDIA_TIME;
 	const elementStartTime =
 		isBeingDragged && dragState.isDragging
-			? dragState.currentTime + dragTimeOffset
+			? addMediaTime({ a: dragState.currentTime, b: dragTimeOffset })
 			: renderElement.startTime;
 	const displayedStartTime = elementStartTime;
 	const displayedDuration = renderElement.duration;
diff --git a/apps/web/src/timeline/components/timeline-playhead.tsx b/apps/web/src/timeline/components/timeline-playhead.tsx
index 4dd3329f..5b1e45ab 100644
--- a/apps/web/src/timeline/components/timeline-playhead.tsx
+++ b/apps/web/src/timeline/components/timeline-playhead.tsx
@@ -7,7 +7,14 @@ import {
 	timelineTimeToSnappedPixels,
 } from "@/timeline";
 import { useTimelinePlayhead } from "@/timeline/hooks/use-timeline-playhead";
-import { TICKS_PER_SECOND } from "@/wasm";
+import {
+	addMediaTime,
+	maxMediaTime,
+	mediaTime,
+	subMediaTime,
+	TICKS_PER_SECOND,
+	ZERO_MEDIA_TIME,
+} from "@/wasm";
 import { useEditor } from "@/editor/use-editor";
 import { TIMELINE_SCROLLBAR_SIZE_PX } from "./layout";
 import { TIMELINE_LAYERS } from "./layers";
@@ -72,17 +79,24 @@ export function TimelinePlayhead({
 
 		event.preventDefault();
 		const fps = editor.project.getActive().settings.fps;
-		const ticksPerFrame = Math.round(
-			(TICKS_PER_SECOND * fps.denominator) / fps.numerator,
-		);
+		const ticksPerFrame = mediaTime({
+			ticks: Math.round(
+				(TICKS_PER_SECOND * fps.denominator) / fps.numerator,
+			),
+		});
 		const direction = event.key === "ArrowRight" ? 1 : -1;
 		const now = editor.playback.getCurrentTime();
-		const nextTime = Math.max(
-			0,
-			Math.min(duration, now + direction * ticksPerFrame),
-		);
+		const nextTime =
+			direction > 0
+				? addMediaTime({ a: now, b: ticksPerFrame })
+				: subMediaTime({ a: now, b: ticksPerFrame });
 
-		editor.playback.seek({ time: nextTime });
+		editor.playback.seek({
+			time: maxMediaTime({
+				a: ZERO_MEDIA_TIME,
+				b: duration < nextTime ? duration : nextTime,
+			}),
+		});
 	};
 
 	return (