# SPDX-License-Identifier: MIT
# Copyright (C) Intel Corporation
#
# Scene Change Detection: OpenCV sample.
# See README.md for prerequisites and inputs. Run: python3 opencv_sample.py

import cv2
import numpy as np

INPUT_VIDEO = "test_video.mp4"
CHANGE_THRESHOLD = 0.45  # Bhattacharyya distance in [0, 1]; higher = more change

cap = cv2.VideoCapture(INPUT_VIDEO)
fps = cap.get(cv2.CAP_PROP_FPS) or 30.0
width = int(cap.get(cv2.CAP_PROP_FRAME_WIDTH))
height = int(cap.get(cv2.CAP_PROP_FRAME_HEIGHT))
writer = cv2.VideoWriter(
    "output_opencv.mp4", cv2.VideoWriter_fourcc(*"mp4v"), fps, (width, height))


def frame_histogram(bgr):
    hsv = cv2.cvtColor(bgr, cv2.COLOR_BGR2HSV)
    hist = cv2.calcHist([hsv], [0, 1], None, [50, 60], [0, 180, 0, 256])
    cv2.normalize(hist, hist, 0, 1, cv2.NORM_MINMAX)
    return hist


prev_hist = None
frame_idx = 0
scene_changes = 0
while True:
    ok, frame = cap.read()
    if not ok:
        break
    frame_idx += 1
    hist = frame_histogram(frame)

    distance = 0.0
    changed = False
    if prev_hist is not None:
        distance = cv2.compareHist(prev_hist, hist, cv2.HISTCMP_BHATTACHARYYA)
        changed = distance >= CHANGE_THRESHOLD
    prev_hist = hist

    if changed:
        scene_changes += 1
        print(f"Frame {frame_idx}: SCENE CHANGE (distance={distance:.3f})",
              flush=True)
    color = (0, 0, 255) if changed else (0, 255, 0)
    label = f"dist={distance:.3f}" + (" CHANGE" if changed else "")
    cv2.putText(frame, label, (10, 30),
                cv2.FONT_HERSHEY_SIMPLEX, 0.8, color, 2)
    writer.write(frame)

cap.release()
writer.release()
print(f"Scene changes detected: {scene_changes}", flush=True)