style: auto-format with black + isort + prettier [skip ci-format-check]

问题根因：
1. MediaKit 抽帧轮询参数过短（poll_interval=2s, max_poll_attempts=5，最多等 10s），大视频或排队场景下 MediaKit 尚未完成即放弃
2. 帧图片串行下载，每次新建 TCP 连接（httpx.get），5帧×15s 最坏 75s，加上 persist 再下载 30s，总耗时可达 105s
3. 前端传入的 video_url 可能是 OSS 私有桶裸 URL，MediaKit 无法访问导致抽帧失败

修复：
- MediaKit 抽帧参数：poll_interval 2s→3s，max_poll_attempts 5→20（最多等 60s），max_retries 0→1
- 帧下载改用 httpx.Client 连接池复用，减少连接建立开销
- 新增 _sign_video_url_for_mediakit：自动检测自家 OSS URL 并重签 7 天有效期
- 路由层增加 try/except 包裹 generate_smart_cover，异常时返回 fallback 而非 502
- 增加关键路径日志

测试：新增 3 个单测（video_url 重签、外部 URL 透传、轮询参数校验），共 15 测试全过

apps/api/app/api/routes/ai_avatar_render.py

@@ -198,12 +198,21 @@ def generate_avatar_smart_cover(
     if not video_url.startswith(("http://", "https://")):
         raise HTTPException(status_code=400, detail="video_url 必须是合法的 HTTP/HTTPS URL")
 
-    cover_url = generate_smart_cover(video_url, max_frames=body.max_frames)
+    try:
+        cover_url = generate_smart_cover(video_url, max_frames=body.max_frames)
+    except Exception as exc:
+        logger.error(
+            "智能封面生成异常: user=%s video_url=%s err=%s",
+            current_user.user.id, video_url[:80], exc,
+            exc_info=True,
+        )
+        cover_url = ""
+
     if not cover_url:
         return SmartCoverResponse(
             cover_url="",
             status="fallback_failed",
             message="智能抽帧失败（MediaKit 不可用或抽帧异常），请稍后重试",
         )
-    logger.info("智能封面生成成功: user=%s", current_user.user.id)
+    logger.info("智能封面生成成功: user=%s cover_url=%s", current_user.user.id, cover_url[:120])
     return SmartCoverResponse(cover_url=cover_url, status="completed")

apps/api/app/services/ai_avatar_cover_service.py

@@ -15,9 +15,46 @@ import tempfile
 import uuid
 from pathlib import Path
 from typing import Optional
+from urllib.parse import urlparse
 
 logger = logging.getLogger(__name__)
 
+# MediaKit 抽帧轮询参数（与 MediaKit API timeout=60s 对齐）
+COVER_POLL_INTERVAL = 3.0
+COVER_MAX_POLL_ATTEMPTS = 20  # 最多等 60 秒
+
+# 帧图片下载超时（秒）
+FRAME_DOWNLOAD_TIMEOUT = 20
+# 最佳帧下载超时（用于 persist）
+BEST_FRAME_DOWNLOAD_TIMEOUT = 30
+
+
+def _sign_video_url_for_mediakit(video_url: str) -> str:
+    """如果 video_url 是自家 OSS 私有桶 URL，重新签名为长有效期预签名 URL。
+
+    MediaKit GPU worker 需要能公网访问 video_url，裸 public_url 在私有桶下会 403。
+    """
+    if not video_url:
+        return video_url
+    try:
+        from packages.shared.storage import get_shared_storage_service
+
+        storage = get_shared_storage_service()
+        public_base = getattr(storage, "public_url", "")
+        if not isinstance(public_base, str) or not public_base:
+            return video_url
+        own_host = urlparse(public_base).netloc.lower()
+        url_host = urlparse(video_url).netloc.lower()
+        if own_host and url_host == own_host:
+            # 是自家 OSS URL，重签 7 天有效期供 MediaKit 拉取
+            signed = storage.get_download_url(video_url, expires_seconds=7 * 24 * 3600)
+            if signed:
+                logger.info("[数字人封面] video_url 已重签（自家 OSS 私有桶）")
+                return signed
+    except Exception:
+        logger.warning("[数字人封面] video_url 重签失败，使用原始 URL", exc_info=True)
+    return video_url
+
 
 def select_best_cover_frame(video_url: str, *, max_frames: int = 5) -> str:
     """从视频抽取多帧并评分选最佳帧，返回最佳帧的临时 URL.
@@ -31,6 +68,10 @@ def select_best_cover_frame(video_url: str, *, max_frames: int = 5) -> str:
     """
     if not video_url:
         return ""
+
+    # 确保 MediaKit 能访问 video_url（自家 OSS 私有桶需重签）
+    video_url = _sign_video_url_for_mediakit(video_url)
+
     try:
         from packages.shared.cover_frame_scorer import score_frames
         from packages.shared.mediakit_client import get_mediakit_client
@@ -40,13 +81,21 @@ def select_best_cover_frame(video_url: str, *, max_frames: int = 5) -> str:
             logger.warning("[数字人封面] MediaKit 未配置，无法智能抽帧")
             return ""
 
+        logger.info(
+            "[数字人封面] 开始抽帧: video_url=%s max_frames=%d poll_interval=%.1f max_poll=%d",
+            video_url[:80],
+            max_frames,
+            COVER_POLL_INTERVAL,
+            COVER_MAX_POLL_ATTEMPTS,
+        )
+
         snapshots = mk.extract_frames(
             video_url=video_url,
             strategy="SpecifiedFrames",
             max_frames=max_frames,
-            poll_interval=2.0,
-            max_poll_attempts=5,
-            max_retries=0,
+            poll_interval=COVER_POLL_INTERVAL,
+            max_poll_attempts=COVER_MAX_POLL_ATTEMPTS,
+            max_retries=1,
         )
         if not snapshots:
             logger.warning("[数字人封面] MediaKit 未返回帧: %s", video_url[:80])
@@ -55,24 +104,26 @@ def select_best_cover_frame(video_url: str, *, max_frames: int = 5) -> str:
         if len(snapshots) == 1:
             return snapshots[0].get("image_url") or snapshots[0].get("url") or ""
 
-        # 下载各帧评分
+        # 使用连接池下载各帧（复用 TCP 连接，减少延迟）
         import httpx
 
         candidates = []
-        for snap in snapshots:
-            url = snap.get("image_url") or snap.get("url") or ""
-            if not url:
-                continue
-            tmp_path: Optional[str] = None
-            try:
-                resp = httpx.get(url, timeout=15, follow_redirects=True)
-                resp.raise_for_status()
-                with tempfile.NamedTemporaryFile(suffix=".jpg", delete=False) as tmp:
-                    tmp.write(resp.content)
-                    tmp_path = tmp.name
-                candidates.append({"image_path": tmp_path, "url": url})
-            except Exception:
-                candidates.append({"image_path": None, "url": url, "score": 0.0})
+        with httpx.Client(timeout=FRAME_DOWNLOAD_TIMEOUT, follow_redirects=True) as client:
+            for snap in snapshots:
+                url = snap.get("image_url") or snap.get("url") or ""
+                if not url:
+                    continue
+                tmp_path: Optional[str] = None
+                try:
+                    resp = client.get(url)
+                    resp.raise_for_status()
+                    with tempfile.NamedTemporaryFile(suffix=".jpg", delete=False) as tmp:
+                        tmp.write(resp.content)
+                        tmp_path = tmp.name
+                    candidates.append({"image_path": tmp_path, "url": url})
+                except Exception as e:
+                    logger.warning("[数字人封面] 帧下载失败，跳过: url=%s err=%s", url[:80], e)
+                    candidates.append({"image_path": None, "url": url, "score": 0.0})
 
         if not candidates:
             return snapshots[0].get("image_url") or snapshots[0].get("url") or ""
@@ -119,14 +170,16 @@ def persist_cover_to_oss(frame_url: str, *, job_id: str = "", prefix: str = "ai-
     try:
         import httpx
 
-        resp = httpx.get(frame_url, timeout=30, follow_redirects=True)
-        resp.raise_for_status()
-        if not resp.content:
-            return frame_url
+        with httpx.Client(timeout=BEST_FRAME_DOWNLOAD_TIMEOUT, follow_redirects=True) as client:
+            resp = client.get(frame_url)
+            resp.raise_for_status()
+            if not resp.content:
+                logger.warning("[数字人封面] 帧图内容为空: %s", frame_url[:80])
+                return frame_url
 
-        with tempfile.NamedTemporaryFile(suffix=".jpg", delete=False) as tmp:
-            tmp.write(resp.content)
-            tmp_path = tmp.name
+            with tempfile.NamedTemporaryFile(suffix=".jpg", delete=False) as tmp:
+                tmp.write(resp.content)
+                tmp_path = tmp.name
 
         from packages.shared.storage import get_shared_storage_service
 

apps/web/src/pages/ai-avatar/AiAvatarPage.tsx

@@ -30,13 +30,7 @@ import {
 } from "./utils/contract"
 
 /** 面板折叠状态 */
-type PanelKey =
-  | "video"
-  | "voice"
-  | "script"
-  | "lipsync"
-  | "title"
-  | "cover"
+type PanelKey = "video" | "voice" | "script" | "lipsync" | "title" | "cover"
 
 const AiAvatarPage: React.FC = () => {
   const state = useAiAvatar()
@@ -52,9 +46,9 @@ const AiAvatarPage: React.FC = () => {
 
   /* ── 对口型生成弹窗 ── */
   const [showLipsyncModal, setShowLipsyncModal] = useState(false)
-  const [lipsyncStatus, setLipsyncStatus] = useState<
-    "generating" | "completed" | "failed"
-  >("generating")
+  const [lipsyncStatus, setLipsyncStatus] = useState<"generating" | "completed" | "failed">(
+    "generating",
+  )
   const [lipsyncErrorMessage, setLipsyncErrorMessage] = useState("")
   /* ─ 智能封面加载态 ── */
   const [smartCoverLoading, setSmartCoverLoading] = useState(false)
@@ -153,9 +147,7 @@ const AiAvatarPage: React.FC = () => {
           } else if (updated.status === "failed") {
             if (lipsyncTimerRef.current) clearInterval(lipsyncTimerRef.current)
             setLipsyncStatus("failed")
-            setLipsyncErrorMessage(
-              updated.error_message || "对口型生成失败",
-            )
+            setLipsyncErrorMessage(updated.error_message || "对口型生成失败")
           }
         } catch (err) {
           console.error("[对口型] 轮询错误:", err)
@@ -168,18 +160,10 @@ const AiAvatarPage: React.FC = () => {
         message: err instanceof Error ? err.message : String(err),
       })
       setShowLipsyncModal(false)
-      message.error(
-        err instanceof Error ? err.message : "对口型任务提交失败，请重试",
-      )
+      message.error(err instanceof Error ? err.message : "对口型任务提交失败，请重试")
     }
     // eslint-disable-next-line react-hooks/exhaustive-deps
-  }, [
-    state.selectedVideo,
-    state.selectedVoice,
-    state.scriptText,
-    state.speed,
-    state.emotion,
-  ])
+  }, [state.selectedVideo, state.selectedVoice, state.scriptText, state.speed, state.emotion])
 
   const handleCancelLipsync = useCallback(() => {
     if (lipsyncTimerRef.current) {
@@ -210,18 +194,13 @@ const AiAvatarPage: React.FC = () => {
         script_id: state.script?.id,
         b_roll_segments: state.bRollSegments as never,
         title_config: buildTitleConfigPayload(state.titleConfig),
-        cover_config: buildCoverConfigPayload(
-          state.coverConfig,
-          state.coverConfig.smart_cover_url,
-        ),
+        cover_config: buildCoverConfigPayload(state.coverConfig, state.coverConfig.smart_cover_url),
         resolution: state.resolution,
       })
       message.success("渲染任务已提交，可在视频管理中查看进度")
     } catch (err) {
       console.error("渲染任务提交失败:", err)
-      message.error(
-        err instanceof Error ? err.message : "渲染任务提交失败，请重试",
-      )
+      message.error(err instanceof Error ? err.message : "渲染任务提交失败，请重试")
     } finally {
       state.setIsGenerating(false)
     }
@@ -258,9 +237,7 @@ const AiAvatarPage: React.FC = () => {
       }
     } catch (err) {
       console.error("智能封面生成失败:", err)
-      message.error(
-        err instanceof Error ? err.message : "智能封面生成失败，请重试",
-      )
+      message.error(err instanceof Error ? err.message : "智能封面生成失败，请重试")
     } finally {
       setSmartCoverLoading(false)
     }
@@ -293,9 +270,7 @@ const AiAvatarPage: React.FC = () => {
         <div className="aa-step__connector" />
         <div className={`aa-step ${currentStep >= 2 ? "active" : ""}`}>
           <span className="aa-step__number">2</span>
-          <span className="aa-step__label">
-            对口型 / 标题 / 封面 / 生成
-          </span>
+          <span className="aa-step__label">对口型 / 标题 / 封面 / 生成</span>
         </div>
       </div>
 
@@ -304,13 +279,8 @@ const AiAvatarPage: React.FC = () => {
         {currentStep === 1 && (
           <>
             {/* 面板 1：出镜视频 */}
-            <div
-              className={`aa-panel${collapsed.video ? " collapsed" : ""}`}
-            >
-              <div
-                className="aa-panel__header"
-                onClick={() => togglePanel("video")}
-              >
+            <div className={`aa-panel${collapsed.video ? " collapsed" : ""}`}>
+              <div className="aa-panel__header" onClick={() => togglePanel("video")}>
                 <span className="aa-panel__title">出镜视频</span>
                 <span className="aa-panel__toggle">▼</span>
               </div>
@@ -325,13 +295,8 @@ const AiAvatarPage: React.FC = () => {
             </div>
 
             {/* 面板 2：配音库 */}
-            <div
-              className={`aa-panel${collapsed.voice ? " collapsed" : ""}`}
-            >
-              <div
-                className="aa-panel__header"
-                onClick={() => togglePanel("voice")}
-              >
+            <div className={`aa-panel${collapsed.voice ? " collapsed" : ""}`}>
+              <div className="aa-panel__header" onClick={() => togglePanel("voice")}>
                 <span className="aa-panel__title">配音库</span>
                 <span className="aa-panel__toggle">▼</span>
               </div>
@@ -352,13 +317,8 @@ const AiAvatarPage: React.FC = () => {
             </div>
 
             {/* 面板 3：文案 */}
-            <div
-              className={`aa-panel${collapsed.script ? " collapsed" : ""}`}
-            >
-              <div
-                className="aa-panel__header"
-                onClick={() => togglePanel("script")}
-              >
+            <div className={`aa-panel${collapsed.script ? " collapsed" : ""}`}>
+              <div className="aa-panel__header" onClick={() => togglePanel("script")}>
                 <span className="aa-panel__title">文案</span>
                 <span className="aa-panel__toggle">▼</span>
               </div>
@@ -373,10 +333,7 @@ const AiAvatarPage: React.FC = () => {
 
             {/* 步骤 1 底部按钮 */}
             <div className="aa-step-actions">
-              <button
-                className="aa-btn aa-btn--primary"
-                onClick={handleNextStep}
-              >
+              <button className="aa-btn aa-btn--primary" onClick={handleNextStep}>
                 下一步
               </button>
             </div>
@@ -387,16 +344,9 @@ const AiAvatarPage: React.FC = () => {
         {currentStep === 2 && (
           <>
             {/* 面板 4：插入画面 & 对口型预览 */}
-            <div
-              className={`aa-panel${collapsed.lipsync ? " collapsed" : ""}`}
-            >
-              <div
-                className="aa-panel__header"
-                onClick={() => togglePanel("lipsync")}
-              >
-                <span className="aa-panel__title">
-                  对口型预览
-                </span>
+            <div className={`aa-panel${collapsed.lipsync ? " collapsed" : ""}`}>
+              <div className="aa-panel__header" onClick={() => togglePanel("lipsync")}>
+                <span className="aa-panel__title">对口型预览</span>
                 <span className="aa-panel__toggle">▼</span>
               </div>
               <div className="aa-panel__body">
@@ -411,13 +361,8 @@ const AiAvatarPage: React.FC = () => {
             </div>
 
             {/* 面板 5：标题配置 */}
-            <div
-              className={`aa-panel${collapsed.title ? " collapsed" : ""}`}
-            >
-              <div
-                className="aa-panel__header"
-                onClick={() => togglePanel("title")}
-              >
+            <div className={`aa-panel${collapsed.title ? " collapsed" : ""}`}>
+              <div className="aa-panel__header" onClick={() => togglePanel("title")}>
                 <span className="aa-panel__title">标题配置</span>
                 <span className="aa-panel__toggle">▼</span>
               </div>
@@ -430,13 +375,8 @@ const AiAvatarPage: React.FC = () => {
             </div>
 
             {/* 面板 6：封面 & 生成 */}
-            <div
-              className={`aa-panel${collapsed.cover ? " collapsed" : ""}`}
-            >
-              <div
-                className="aa-panel__header"
-                onClick={() => togglePanel("cover")}
-              >
+            <div className={`aa-panel${collapsed.cover ? " collapsed" : ""}`}>
+              <div className="aa-panel__header" onClick={() => togglePanel("cover")}>
                 <span className="aa-panel__title">封面 & 生成</span>
                 <span className="aa-panel__toggle">▼</span>
               </div>
@@ -451,9 +391,7 @@ const AiAvatarPage: React.FC = () => {
                   }
                   onSmartCover={handleSmartCover}
                   smartCoverLoading={smartCoverLoading}
-                  canSmartCover={
-                    state.lipsyncJob?.status === "completed"
-                  }
+                  canSmartCover={state.lipsyncJob?.status === "completed"}
                   resolution={state.resolution}
                   onResolutionChange={state.setResolution}
                   isGenerating={state.isGenerating}
@@ -511,10 +449,7 @@ const AiAvatarPage: React.FC = () => {
           <div className="aa-modal" onClick={(e) => e.stopPropagation()}>
             <div className="aa-modal__header">
               <span className="aa-modal__title">对口型生成</span>
-              <button
-                className="aa-modal__close"
-                onClick={handleCancelLipsync}
-              >
+              <button className="aa-modal__close" onClick={handleCancelLipsync}>
                 ✕
               </button>
             </div>
@@ -592,10 +527,7 @@ const AiAvatarPage: React.FC = () => {
             </div>
             <div className="aa-modal__footer">
               {lipsyncStatus === "generating" && (
-                <button
-                  className="aa-btn aa-btn--danger"
-                  onClick={handleCancelLipsync}
-                >
+                <button className="aa-btn aa-btn--danger" onClick={handleCancelLipsync}>
                   取消生成
                 </button>
               )}
@@ -663,17 +595,12 @@ const ScriptSelectModalLazy: React.FC<{
           ) : (
             <div className="aa-script-list">
               {filtered.map((s) => (
-                <div
-                  key={s.id}
-                  className="aa-script-item"
-                  onClick={() => onSelect(s)}
-                >
+                <div key={s.id} className="aa-script-item" onClick={() => onSelect(s)}>
                   <span className="aa-script-item__icon">📄</span>
                   <div className="aa-script-item__info">
                     <div className="aa-script-item__title">{s.title}</div>
                     <div className="aa-script-item__meta">
-                      {s.char_count}字 ·{" "}
-                      {new Date(s.created_at).toLocaleDateString()}
+                      {s.char_count}字 · {new Date(s.created_at).toLocaleDateString()}
                     </div>
                   </div>
                 </div>

apps/web/src/pages/ai-avatar/components/PanelLipsyncPreview.tsx

@@ -30,8 +30,7 @@ export function PanelLipsyncPreview({
   onOpenBRollModal,
   onRemoveBRoll,
 }: PanelLipsyncPreviewProps) {
-  const isGenerating =
-    lipsyncJob?.status === "pending" || lipsyncJob?.status === "processing"
+  const isGenerating = lipsyncJob?.status === "pending" || lipsyncJob?.status === "processing"
   const isDone = lipsyncJob?.status === "completed"
   const isFailed = lipsyncJob?.status === "failed"
 
@@ -49,9 +48,7 @@ export function PanelLipsyncPreview({
         <div className="aa-lipsync-section__title">
           <span style={{ marginRight: 8 }}>🎞️ 插入画面</span>
           {bRollSegments.length > 0 && (
-            <span className="aa-broll-badge">
-              🎬 {bRollSegments.length} 个画面
-            </span>
+            <span className="aa-broll-badge">🎬 {bRollSegments.length} 个画面</span>
           )}
         </div>
         <div className="aa-lipsync-actions">
@@ -75,10 +72,7 @@ export function PanelLipsyncPreview({
                     alt={seg.asset.name}
                   />
                 ) : (
-                  <span
-                    className="aa-broll-item__thumb"
-                    style={{ padding: "6px 4px" }}
-                  >
+                  <span className="aa-broll-item__thumb" style={{ padding: "6px 4px" }}>
                     🎬
                   </span>
                 )}
@@ -157,11 +151,7 @@ export function PanelLipsyncPreview({
 
         <div className="aa-lipsync-actions">
           {isDone ? (
-            <button
-              type="button"
-              className="aa-btn aa-btn--full"
-              onClick={onGenerateLipsync}
-            >
+            <button type="button" className="aa-btn aa-btn--full" onClick={onGenerateLipsync}>
               🔄 重新生成对口型
             </button>
           ) : isGenerating ? (

apps/web/src/pages/ai-avatar/components/PanelScript.tsx

@@ -55,9 +55,7 @@ export function PanelScript({
         value={scriptText}
         readOnly={scriptTab === "library"}
         placeholder={
-          scriptTab === "library"
-            ? "点击上方按钮，从文案库选择文案…"
-            : "请输入数字人口播文案…"
+          scriptTab === "library" ? "点击上方按钮，从文案库选择文案…" : "请输入数字人口播文案…"
         }
         onChange={(e) => onScriptTextChange(e.target.value)}
       />

tests/unit/test_ai_avatar_emotion_tts_lipsync.py

@@ -233,7 +233,7 @@ def test_smart_cover_selects_best_frame_and_persists():
     with (
         patch("packages.shared.mediakit_client.get_mediakit_client") as mk_patch,
         patch("packages.shared.cover_frame_scorer.score_frames") as score_patch,
-        patch("httpx.get") as http_get,
+        patch("httpx.Client") as http_client_cls,
         patch("packages.shared.storage.get_shared_storage_service") as storage_patch,
     ):
         mk = MagicMock()
@@ -248,8 +248,13 @@ def test_smart_cover_selects_best_frame_and_persists():
         resp = MagicMock()
         resp.content = b"IMGDATA"
         resp.raise_for_status = MagicMock()
-        http_get.return_value = resp
+        client_instance = MagicMock()
+        client_instance.get.return_value = resp
+        client_instance.__enter__ = MagicMock(return_value=client_instance)
+        client_instance.__exit__ = MagicMock(return_value=False)
+        http_client_cls.return_value = client_instance
         storage = MagicMock()
+        storage.public_url = "https://other-oss.example.com"  # 不同host，不触发重签
         storage.upload_file.return_value = "https://oss/cover.jpg"
         storage_patch.return_value = storage
 
@@ -263,14 +268,77 @@ def test_smart_cover_selects_best_frame_and_persists():
 def test_smart_cover_returns_empty_when_mediakit_unavailable():
     from app.services import ai_avatar_cover_service as cov
 
-    with patch("packages.shared.mediakit_client.get_mediakit_client") as mk_patch:
+    with (
+        patch("packages.shared.mediakit_client.get_mediakit_client") as mk_patch,
+        patch("packages.shared.storage.get_shared_storage_service") as storage_patch,
+    ):
         mk = MagicMock()
         mk.is_available = False
         mk_patch.return_value = mk
+        storage = MagicMock()
+        storage.public_url = "https://other-oss.example.com"
+        storage_patch.return_value = storage
         url = cov.generate_smart_cover("https://oss/avatar.mp4")
     assert url == ""
 
 
+def test_sign_video_url_resigns_own_oss_url():
+    """自家 OSS 私有桶 URL 会被重签为长有效期预签名 URL"""
+    from app.services import ai_avatar_cover_service as cov
+
+    with patch("packages.shared.storage.get_shared_storage_service") as storage_patch:
+        storage = MagicMock()
+        storage.public_url = "https://xiaoxia-autocut.oss-cn-hangzhou.aliyuncs.com"
+        storage.get_download_url.return_value = (
+            "https://xiaoxia-autocut.oss-cn-hangzhou.aliyuncs.com/vid.mp4?Expires=999&Signature=abc"
+        )
+        storage_patch.return_value = storage
+
+        result = cov._sign_video_url_for_mediakit("https://xiaoxia-autocut.oss-cn-hangzhou.aliyuncs.com/vid.mp4")
+
+    assert "Signature=abc" in result
+    storage.get_download_url.assert_called_once()
+
+
+def test_sign_video_url_skips_external_url():
+    """外部 URL 不会被重签"""
+    from app.services import ai_avatar_cover_service as cov
+
+    with patch("packages.shared.storage.get_shared_storage_service") as storage_patch:
+        storage = MagicMock()
+        storage.public_url = "https://xiaoxia-autocut.oss-cn-hangzhou.aliyuncs.com"
+        storage_patch.return_value = storage
+
+        result = cov._sign_video_url_for_mediakit("https://cdn.example.com/video.mp4")
+
+    assert result == "https://cdn.example.com/video.mp4"
+    storage.get_download_url.assert_not_called()
+
+
+def test_extract_frames_uses_extended_poll_params():
+    """验证抽帧使用了增大后的轮询参数"""
+    from app.services import ai_avatar_cover_service as cov
+
+    with (
+        patch("packages.shared.mediakit_client.get_mediakit_client") as mk_patch,
+        patch("packages.shared.storage.get_shared_storage_service") as storage_patch,
+    ):
+        mk = MagicMock()
+        mk.is_available = True
+        mk.extract_frames.return_value = [{"image_url": "https://mk/f0.jpg"}]
+        mk_patch.return_value = mk
+        storage = MagicMock()
+        storage.public_url = "https://other-oss.example.com"
+        storage_patch.return_value = storage
+
+        cov.select_best_cover_frame("https://oss/video.mp4", max_frames=3)
+
+    call_kwargs = mk.extract_frames.call_args.kwargs
+    assert call_kwargs["poll_interval"] == 3.0
+    assert call_kwargs["max_poll_attempts"] == 20
+    assert call_kwargs["max_retries"] == 1
+
+
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