refactor: 统一封面生成管道 — 从渲染后视频抽帧作为封面 (#1371)

Co-authored-by: xiaoxia <dev@xiaoxiajianji.com>
Co-committed-by: xiaoxia <dev@xiaoxiajianji.com>

apps/worker/video_processing/render_adapter.py

@@ -81,9 +81,7 @@ class RenderAdapterResult:
     failed_clip_ids: list[str] = None  # 失败的 clip id 列表
     error_message: str = ""
     error_detail: str = ""  # 详细错误信息（如 ffmpeg stderr），用于排查
-    cover_candidates: list[dict] | None = (
-        None  # 封面候选帧 [{"image_url": "...", "frame_time": 5.0, "storage_key": "..."}]
-    )
+    cover_url: str = ""  # 封面图片 URL（从渲染后视频抽帧，天然带标题）
 
     def __post_init__(self):
         if self.rendered_clip_ids is None:
@@ -562,43 +560,33 @@ class RenderAdapter:
         storage_key = f"rendered/{plan_id}/{job_id or plan_id}.mp4"
         output_url = upload_to_oss(result.output_path, storage_key)
 
-        self._report_progress(progress_cb, 90.0, "生成封面缩略图")
+        self._report_progress(progress_cb, 90.0, "抽取封面帧")
 
-        # 6. 生成封面缩略图
-        thumbnail_url = ""
+        # 6. 从已渲染视频抽取封面帧（标题已通过 ASS 字幕烧录，封面天然带标题）
+        cover_url = ""
+        cover_frame_path = None
         try:
-            from video_processing.thumbnail_generator import generate_and_upload_thumbnail
+            from video_processing.thumbnail_generator import extract_first_frame
 
-            thumb_storage_key = f"rendered/{plan_id}/thumbnail.jpg"
-            thumbnail_url = generate_and_upload_thumbnail(str(result.output_path), thumb_storage_key)
-        except Exception as thumb_err:
-            logger.warning(
-                "[render-adapter] 缩略图生成失败（不影响主流程）: plan_id=%s error=%s",
-                plan_id,
-                thumb_err,
-            )
-
-        # 7. 抽取封面候选帧并上传 OSS（失败不阻断主流程）
-        cover_candidates = None
-        try:
-            from video_processing.thumbnail_generator import extract_and_upload_cover_frames
-
-            # 从 plan config 提取标题文字，叠加到封面候选帧上
-            _title_cfg = (plan_config or {}).get("title", {}) or {}
-            _title_text = (_title_cfg.get("text", "") or "").strip() if _title_cfg.get("enabled", True) else ""
-
-            cover_candidates = extract_and_upload_cover_frames(
-                str(result.output_path), plan_id, num_frames=3, title_text=_title_text
-            )
-            if cover_candidates:
+            cover_frame_path = extract_first_frame(str(result.output_path), width=640)
+            cover_storage_key = f"rendered/{plan_id}/cover.jpg"
+            try:
+                cover_url = upload_to_oss(cover_frame_path, cover_storage_key) or ""
+            finally:
+                if cover_frame_path:
+                    try:
+                        Path(cover_frame_path).unlink(missing_ok=True)
+                    except Exception:
+                        pass
+            if cover_url:
                 logger.info(
-                    "[render-adapter] 封面候选帧生成成功: plan_id=%s count=%d",
+                    "[render-adapter] 封面帧提取成功: plan_id=%s url=%s",
                     plan_id,
-                    len(cover_candidates),
+                    cover_url[:80],
                 )
         except Exception as cover_err:
             logger.warning(
-                "[render-adapter] 封面候选帧生成失败（不影响主流程）: plan_id=%s error=%s",
+                "[render-adapter] 封面帧提取失败（不影响主流程）: plan_id=%s error=%s",
                 plan_id,
                 cover_err,
             )
@@ -626,7 +614,7 @@ class RenderAdapter:
             success=True,
             output_url=output_url or "",
             output_path=result.output_path,
-            thumbnail_url=thumbnail_url,
+            thumbnail_url=cover_url,
             duration=result.duration,
             file_size=result.file_size,
             width=result.width,
@@ -634,7 +622,7 @@ class RenderAdapter:
             clip_count=len(clips),
             rendered_clip_ids=final_rendered_ids,
             failed_clip_ids=final_failed_ids,
-            cover_candidates=cover_candidates,
+            cover_url=cover_url,
         )
 
     def render_from_memory(