fix: ソースFPSの認識の問題

server/main.py

@@ -53,6 +53,40 @@ from server.detector import get_detector
 
 app = FastAPI(title="Face Mask Inference Server")
 
+
+def _get_r_frame_rate(video_path: str) -> tuple:
+    """ffprobe でコンテナ宣言の r_frame_rate を取得する。
+
+    Returns:
+        (fps_float, fps_str): fps_str は "120/1" のような分数文字列。
+        取得失敗時は (0.0, "")。
+    """
+    try:
+        result = subprocess.run(
+            [
+                "ffprobe", "-v", "error",
+                "-select_streams", "v:0",
+                "-show_entries", "stream=r_frame_rate",
+                "-of", "default=noprint_wrappers=1:nokey=1",
+                video_path,
+            ],
+            capture_output=True,
+            text=True,
+            timeout=10,
+        )
+        if result.returncode == 0:
+            rate_str = result.stdout.strip()
+            if "/" in rate_str:
+                num, den = rate_str.split("/")
+                fps_float = float(num) / float(den)
+            else:
+                fps_float = float(rate_str)
+                rate_str = str(fps_float)
+            return fps_float, rate_str
+    except Exception:
+        pass
+    return 0.0, ""
+
 # GPU status cache
 _gpu_status_cache = None
 
@@ -142,8 +176,33 @@ def _build_ffmpeg_vaapi_writer(
     fps: float,
     width: int,
     height: int,
+    out_fps_str: str = "",
 ) -> _FFmpegPipeWriter:
-    """Create ffmpeg h264_vaapi writer with QP=24 (balanced quality/speed)."""
+    """Create ffmpeg h264_vaapi writer with QP=24 (balanced quality/speed).
+
+    fps: ソース動画の avg_frame_rate（rawパイプの入力レート）
+    out_fps_str: 出力コンテナに宣言する r_frame_rate（"120/1" 等）。
+                 ソースと異なる場合は fps フィルタでフレームを補完する。
+    """
+    # ソースの avg_fps と出力の r_fps が有意に異なる場合のみ fps フィルタを挿入
+    needs_fps_filter = bool(out_fps_str)
+    if needs_fps_filter:
+        try:
+            if "/" in out_fps_str:
+                num, den = out_fps_str.split("/")
+                out_fps_float = float(num) / float(den)
+            else:
+                out_fps_float = float(out_fps_str)
+            needs_fps_filter = abs(out_fps_float - fps) > 0.01
+        except ValueError:
+            needs_fps_filter = False
+
+    if needs_fps_filter:
+        vf = f"format=nv12,fps={out_fps_str},hwupload"
+        print(f"[FaceMask] fps filter: {fps:.3f} -> {out_fps_str}")
+    else:
+        vf = "format=nv12,hwupload"
+
     cmd = [
         "ffmpeg",
         "-hide_banner",
@@ -164,7 +223,7 @@ def _build_ffmpeg_vaapi_writer(
         "-",
         "-an",
         "-vf",
-        "format=nv12,hwupload",
+        vf,
         "-c:v",
         "h264_vaapi",
         "-qp",
@@ -180,13 +239,14 @@ def _build_video_writer(
     fps: float,
     width: int,
     height: int,
+    out_fps_str: str = "",
 ) -> object:
     """Create writer with VAAPI preference and OpenCV fallback."""
     format_key = fmt.lower()
 
     if format_key in {"mp4", "mov"}:
         try:
-            writer = _build_ffmpeg_vaapi_writer(output_path, fps, width, height)
+            writer = _build_ffmpeg_vaapi_writer(output_path, fps, width, height, out_fps_str)
             print("[FaceMask] Using output encoder: ffmpeg h264_vaapi (-qp 24)")
             return writer
         except Exception as e:
@@ -417,6 +477,15 @@ def process_bake_task(task_id: str, req: BakeRequest):
         src_frames = int(temp_cap.get(cv2.CAP_PROP_FRAME_COUNT))
         temp_cap.release()
 
+        # ffprobe で r_frame_rate を取得し、出力コンテナの宣言 FPS をソースに合わせる。
+        # 例: 120fps タイムベースで記録された 60fps 動画は r_frame_rate=120/1 だが
+        # cv2 は avg_frame_rate=60fps を返すため、Bake 後に Blender がFPSを別値で認識してしまう。
+        r_fps_float, r_fps_str = _get_r_frame_rate(req.video_path)
+        if r_fps_float > 0:
+            print(f"[FaceMask] r_frame_rate={r_fps_str}, avg_fps={src_fps:.3f}")
+        else:
+            r_fps_str = ""
+
         if src_width <= 0 or src_height <= 0:
             tasks[task_id].status = TaskStatus.FAILED
             tasks[task_id].message = "Invalid source video dimensions"
@@ -617,7 +686,7 @@ def process_bake_task(task_id: str, req: BakeRequest):
             frame_count = 0
             writer = None
             try:
-                writer = _build_video_writer(req.output_path, req.format, src_fps, src_width, src_height)
+                writer = _build_video_writer(req.output_path, req.format, src_fps, src_width, src_height, r_fps_str)
 
                 while True:
                     if cancel_event and cancel_event.is_set():
@@ -859,13 +928,20 @@ def get_video_info(req: VideoInfoRequest):
         raise HTTPException(status_code=400, detail="Failed to open video")
 
     try:
-        fps = float(cap.get(cv2.CAP_PROP_FPS) or 0.0)
+        avg_fps = float(cap.get(cv2.CAP_PROP_FPS) or 0.0)
         width = int(cap.get(cv2.CAP_PROP_FRAME_WIDTH) or 0)
         height = int(cap.get(cv2.CAP_PROP_FRAME_HEIGHT) or 0)
         frame_count = int(cap.get(cv2.CAP_PROP_FRAME_COUNT) or 0)
     finally:
         cap.release()
 
+    # Blender は r_frame_rate でタイムライン配置を計算するため、
+    # cv2 の avg_frame_rate ではなく r_frame_rate を fps として返す。
+    # 例: 120fps タイムベース記録の 60fps 動画で r_frame_rate=120 を返すことで
+    # compute_strip_frame_range の fps_ratio が Blender の解釈と一致する。
+    r_fps_float, _ = _get_r_frame_rate(req.video_path)
+    fps = r_fps_float if r_fps_float > 0 else avg_fps
+
     return {
         "video_path": req.video_path,
         "fps": fps,