feat: enhance candidate ranking logic and improve video seeking functionality

src/analysis/candidateRanking.ts

@@ -39,16 +39,16 @@ export function rankAndTrimCandidates(
   for (let bucket = 0; bucket < bucketCount; bucket++) {
     const start = bucket * bucketSize;
     const end = bucket === bucketCount - 1 ? duration + 0.001 : start + bucketSize;
-    const best = pool
-      .filter((candidate) => candidate.time >= start && candidate.time < end)
-      .sort((a, b) => b.score - a.score)[0];
+    const best = bestCandidateInWindow(pool, start, end);
 
-    if (best && respectsMinGap([...selected.values()], best, minGapSeconds)) {
+    if (best) {
       selected.set(frameKey(best.time), best);
     }
   }
 
-  for (const candidate of [...pool].sort((a, b) => b.score - a.score)) {
+  for (const candidate of [...pool].sort(
+    (a, b) => temporalCoverageScore(selected, b, duration) - temporalCoverageScore(selected, a, duration),
+  )) {
     if (selected.size >= targetCount) break;
     if (respectsMinGap([...selected.values()], candidate, minGapSeconds)) {
       selected.set(frameKey(candidate.time), candidate);
@@ -89,3 +89,34 @@ function frameKey(time: number) {
 function respectsMinGap(selected: ScoredFrame[], candidate: ScoredFrame, minGapSeconds: number) {
   return selected.every((item) => Math.abs(item.time - candidate.time) >= minGapSeconds);
 }
+
+function bestCandidateInWindow(candidates: ScoredFrame[], start: number, end: number) {
+  const windowCandidates = candidates.filter((candidate) => candidate.time >= start && candidate.time < end);
+  if (windowCandidates.length === 0) {
+    return undefined;
+  }
+
+  const floor = percentile(windowCandidates, 0.5) * 0.8;
+  return windowCandidates
+    .filter((candidate) => candidate.score >= floor)
+    .sort((a, b) => b.score - a.score)[0];
+}
+
+function temporalCoverageScore(
+  selected: Map<string, ScoredFrame>,
+  candidate: ScoredFrame,
+  duration: number,
+) {
+  const selectedValues = [...selected.values()];
+  if (selectedValues.length === 0) {
+    return candidate.score;
+  }
+
+  const nearestDistance = Math.min(
+    ...selectedValues.map((item) => Math.abs(item.time - candidate.time)),
+    candidate.time,
+    Math.max(0, duration - candidate.time),
+  );
+
+  return nearestDistance * 2 + candidate.score;
+}

src/media/video.ts

@@ -21,9 +21,12 @@ export async function waitForVideoMetadata(video: HTMLVideoElement): Promise<voi
 }
 
 export async function seekVideo(video: HTMLVideoElement, time: number): Promise<void> {
-  const target = Math.min(Math.max(time, 0), video.duration || time);
+  const duration = Number.isFinite(video.duration) ? video.duration : time;
+  const frameSafety = 1 / 120;
+  const target = Math.min(Math.max(time, 0), Math.max(0, duration - frameSafety));
 
   if (Math.abs(video.currentTime - target) < 0.01 && video.readyState >= 2) {
+    await waitForRenderableFrame(video);
     return;
   }
 
@@ -53,4 +56,25 @@ export async function seekVideo(video: HTMLVideoElement, time: number): Promise<
       queueMicrotask(finish);
     }
   });
+
+  await waitForRenderableFrame(video);
+}
+
+async function waitForRenderableFrame(video: HTMLVideoElement): Promise<void> {
+  if ("requestVideoFrameCallback" in video) {
+    await new Promise<void>((resolve) => {
+      const handle = (
+        video as HTMLVideoElement & {
+          requestVideoFrameCallback: (callback: () => void) => number;
+        }
+      ).requestVideoFrameCallback(() => resolve());
+
+      if (!handle && video.readyState >= 2) {
+        resolve();
+      }
+    });
+    return;
+  }
+
+  await new Promise<void>((resolve) => requestAnimationFrame(() => requestAnimationFrame(() => resolve())));
 }