fix: Canvas description缓存+关键帧容错+data字段修正

- 添加 descriptionCache ref，从第一个分片提取后缓存供后续分片使用
- configure 前添加调试日志确认 description 是否正确传递
- EncodedVideoChunk data 字段：sample.data.buffer → sample.data
- 添加关键帧容错：跳过第一个 sync 之前的非关键帧
- destroy 时清理 descriptionCache

apps/web/src/pages/generate/hooks/useCanvasPlayer.ts

@@ -204,6 +204,7 @@ export function useCanvasPlayer(
   const videoDimRef = useRef<{ width: number; height: number }>({ width: 0, height: 0 })
   const isDestroyedRef = useRef(false)
   const lastProgressUpdateRef = useRef<number>(0)
+  const descriptionCache = useRef<Map<string, ArrayBuffer>>(new Map())
 
   // 计算总时长
   const totalDuration = segments.reduce((sum, seg) => sum + (seg.endTime - seg.startTime), 0)
@@ -277,7 +278,20 @@ export function useCanvasPlayer(
         }
 
         // 提取编解码器配置数据（HEVC 必需，H.264 也需要）
-        const description = extractCodecDescription(buffer)
+        let description = extractCodecDescription(buffer)
+
+        // 如果当前分片没有 description，尝试从缓存获取（后续分片可能不含 moov box）
+        if (!description) {
+          for (const cached of descriptionCache.current.values()) {
+            description = cached
+            break
+          }
+        }
+
+        // 如果找到了 description，缓存起来供后续分片使用
+        if (description) {
+          descriptionCache.current.set(segment.assetId, description)
+        }
 
         meta = {
           assetId: segment.assetId,
@@ -338,6 +352,14 @@ export function useCanvasPlayer(
         },
       })
 
+      console.log("[useCanvasPlayer] configure:", {
+        codec: meta.codec,
+        description: meta.description,
+        descriptionByteLength: meta.description?.byteLength,
+        videoWidth: meta.videoWidth,
+        videoHeight: meta.videoHeight,
+      })
+
       try {
         await decoder.configure({
           codec: meta.codec,
@@ -388,16 +410,23 @@ export function useCanvasPlayer(
       // 等待 samples 收集完成（mp4box start() 是同步的）
       await new Promise((resolve) => setTimeout(resolve, 10))
 
-      // 送入解码器
+      // 送入解码器（跳过第一个关键帧之前的非关键帧）
+      let hasKeyFrame = false
       for (const sample of samplesCollected) {
         if (!sample.data || isDestroyedRef.current) continue
         if (decoder.state === "closed") break
 
+        if (!hasKeyFrame && !sample.is_sync) {
+          console.warn("[useCanvasPlayer] Skipping non-keyframe chunk before first sync")
+          continue
+        }
+        if (sample.is_sync) hasKeyFrame = true
+
         const chunk = new EncodedVideoChunk({
           type: sample.is_sync ? "key" : "delta",
           timestamp: (sample.cts / meta.timescale) * 1_000_000,
           duration: (sample.duration / meta.timescale) * 1_000_000,
-          data: sample.data.buffer as ArrayBuffer,
+          data: sample.data,
         })
 
         try {
@@ -590,6 +619,7 @@ export function useCanvasPlayer(
     frameQueueRef.current.clear()
     segmentDataRef.current.clear()
     segmentMetaRef.current = []
+    descriptionCache.current.clear()
   }, [])
 
   // ── 预加载下一个片段的数据 ──