fix: FFmpeg mjpeg 缩略图/封面生成添加 format=yuvj420p

修复 FFmpeg 新版中 mjpeg 编码器拒绝非全范围 YUV 输入的问题：
- thumbnail_generator.py: scale filter 添加 format=yuvj420p
- processor.py: 添加 pix_fmt=yuvj420p
- cover_generator.py: 两处 vf filter 添加 format=yuvj420p
- cover_service.py: vf filter + simple fallback 添加 pix_fmt
- asset_analyzer.py: 添加 -pix_fmt yuvj420p

修复错误: Non full-range YUV is non-standard, set strict_std_compliance
to at most unofficial to use it.

apps/api/app/services/cover_service.py

@@ -215,7 +215,7 @@ class CoverService:
         import subprocess
 
         # scale + crop 实现 cover 裁剪
-        vf = f"scale={width}:{height}:force_original_aspect_ratio=increase," f"crop={width}:{height}"
+        vf = f"scale={width}:{height}:force_original_aspect_ratio=increase," f"crop={width}:{height},format=yuvj420p"
 
         command = [
             "ffmpeg",
@@ -258,6 +258,8 @@ class CoverService:
                     "1",
                     "-q:v",
                     str(quality),
+                    "-pix_fmt",
+                    "yuvj420p",
                     "-f",
                     "mjpeg",
                     str(output_path),

apps/worker/video_processing/cover_generator.py

@@ -93,7 +93,7 @@ class CoverGenerator:
             time_sec = 0
 
         # scale + crop 实现 cover 裁剪（铺满输出尺寸）
-        vf = f"scale={width}:{height}:force_original_aspect_ratio=increase," f"crop={width}:{height}"
+        vf = f"scale={width}:{height}:force_original_aspect_ratio=increase," f"crop={width}:{height},format=yuvj420p"
 
         command = [
             FFMPEG_BIN,
@@ -281,7 +281,7 @@ class CoverGenerator:
         output_path.parent.mkdir(parents=True, exist_ok=True)
 
         # scale + crop 实现 cover 裁剪
-        vf = f"scale={width}:{height}:force_original_aspect_ratio=increase," f"crop={width}:{height}"
+        vf = f"scale={width}:{height}:force_original_aspect_ratio=increase," f"crop={width}:{height},format=yuvj420p"
 
         command = [
             FFMPEG_BIN,

apps/worker/video_processing/processor.py

@@ -159,7 +159,7 @@ class VideoProcessor:
         try:
             (
                 ffmpeg.input(video_path, ss=timestamp)
-                .output(output_path, vframes=1, format="image2", vcodec="mjpeg")
+                .output(output_path, vframes=1, format="image2", vcodec="mjpeg", pix_fmt="yuvj420p")
                 .overwrite_output()
                 .run(capture_stdout=True, capture_stderr=True)
             )

apps/worker/video_processing/thumbnail_generator.py

@@ -60,7 +60,7 @@ def extract_first_frame(
         # -ss 放在 -i 前面（input seeking，更快但精度稍低，缩略图够用）
         # -vframes 1 只取一帧
         # -q:v 2 jpeg 高质量
-        scale_filter = f"scale={width}:{height}:force_original_aspect_ratio=decrease"
+        scale_filter = f"scale={width}:{height}:force_original_aspect_ratio=decrease,format=yuvj420p"
         cmd = [
             FFMPEG_BIN,
             "-y",

apps/worker/worker_app/tasks/asset_analyzer.py

@@ -157,6 +157,8 @@ class AssetAnalyzer:
                     "1",
                     "-q:v",
                     "2",  # 高质量
+                    "-pix_fmt",
+                    "yuvj420p",  # mjpeg 需要全范围 YUV
                     "-f",
                     "image2",
                     output_path,