[BugFix] fix paddleocr prefix cache bug (#4625)

* fix paddleocr prefix cache bug

* disable prefix-caching in ocr

fastdeploy/input/paddleocr_vl_processor/process_video.py

@@ -0,0 +1,82 @@
+"""
+# Copyright (c) 2025 PaddlePaddle Authors. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""
+
+import math
+from typing import Optional, Union
+
+import numpy as np
+
+
+def sample_frames(
+    frame_factor: int,
+    min_frames: int,
+    max_frames: int,
+    metadata: Optional[dict] = None,
+    fps: Optional[Union[int, float]] = None,
+    num_frames: Optional[int] = None,
+):
+    """
+    Sample frames from video according to specified criteria.
+
+    Args:
+        frame_factor: Ensure sampled frames are multiples of this factor
+        min_frames: Minimum number of frames to sample
+        max_frames: Maximum number of frames to sample
+        metadata: Video metadata containing fps information
+        fps: Target frames per second for sampling
+        num_frames: Exact number of frames to sample
+
+    Returns:
+        np.ndarray: Sampled video frames
+
+    Raises:
+        ValueError: If both fps and num_frames are specified,
+                   or if required metadata is missing,
+                   or if requested frames exceed available frames
+    """
+    if fps > 0 and num_frames > 0:
+        raise ValueError("`num_frames` and `fps` are mutually exclusive arguments, please use only one!")
+
+    total_num_frames = metadata["num_of_frame"]
+
+    # If num_frames is not given but fps is, calculate num_frames from fps
+    if num_frames > 0:
+        num_frames = round(num_frames / frame_factor) * frame_factor
+    elif fps > 0:
+        if metadata is None:
+            raise ValueError(
+                "Asked to sample `fps` frames per second but no video metadata was provided which is required when sampling with `fps`. "
+                "Please pass in `VideoMetadata` object or use a fixed `num_frames` per input video"
+            )
+        max_frames = math.floor(min(max_frames, total_num_frames) / frame_factor) * frame_factor
+        num_frames = total_num_frames / metadata["fps"] * fps
+        num_frames = min(min(max(num_frames, min_frames), max_frames), total_num_frames)
+        num_frames = math.floor(num_frames / frame_factor) * frame_factor
+    if num_frames > total_num_frames:
+        raise ValueError(
+            f"Video can't be sampled. The inferred `num_frames={num_frames}` exceeds `total_num_frames={total_num_frames}`. "
+            "Decrease `num_frames` or `fps` for sampling."
+        )
+
+    # Calculate frame indices based on sampling strategy
+    if num_frames > 0:
+        # Evenly spaced sampling for target frame count
+        indices = np.arange(0, total_num_frames, total_num_frames / num_frames).astype(np.int32)
+    else:
+        # Keep all frames if no sampling requested
+        indices = np.arange(0, total_num_frames).astype(np.int32)
+
+    return indices