utils/video.py

from typing import List, Tuple

import cv2
import numpy as np


def extract_frames(video_path: str) -> Tuple[List[np.ndarray], float, int, int]:
    cap = cv2.VideoCapture(video_path)
    if not cap.isOpened():
        raise ValueError("Unable to open video.")

    fps = cap.get(cv2.CAP_PROP_FPS) or 0.0
    width = int(cap.get(cv2.CAP_PROP_FRAME_WIDTH))
    height = int(cap.get(cv2.CAP_PROP_FRAME_HEIGHT))

    frames: List[np.ndarray] = []
    success, frame = cap.read()
    while success:
        frames.append(frame)
        success, frame = cap.read()

    cap.release()

    if not frames:
        raise ValueError("Video decode produced zero frames.")

    return frames, fps, width, height


def write_video(frames: List[np.ndarray], output_path: str, fps: float, width: int, height: int) -> None:
    if not frames:
        raise ValueError("No frames available for writing.")
    fourcc = cv2.VideoWriter_fourcc(*"mp4v")
    writer = cv2.VideoWriter(output_path, fourcc, fps or 1.0, (width, height))
    if not writer.isOpened():
        raise ValueError("Failed to open VideoWriter.")

    for frame in frames:
        writer.write(frame)

    writer.release()