Timestamps provide a virtual timeline in a sequence of scenes captured from an aerial drone video and it is highly relevant when there are multiple tours.  

For example, the following code demonstrates how to correlate timestamps from extracted frames without doing indexing by leveraging sequence in frames from the video. Indexing of video is already demonstrated in the references in the previous articles. 

import cv2 
import os 
 
def format_timestamp(seconds): 
    # Format seconds into HH:MM:SS.mmm 
    hours = int(seconds // 3600) 
    minutes = int((seconds % 3600) // 60) 
    secs = int(seconds % 60) 
    millis = int((seconds - int(seconds)) * 1000) 
    return f"{hours:02}:{minutes:02}:{secs:02}.{millis:03}" 
 
def extract_key_frames(video_path, output_dir, num_frames=5): 
    cap = cv2.VideoCapture(video_path) 
    if not cap.isOpened(): 
        raise IOError(f"Cannot open video file: {video_path}") 
 
    total_frames = int(cap.get(cv2.CAP_PROP_FRAME_COUNT)) 
    fps = cap.get(cv2.CAP_PROP_FPS) 
    duration_sec = total_frames / fps 
 
    print(f"Video FPS: {fps}") 
    print(f"Total frames: {total_frames}") 
    print(f"Duration: {duration_sec:.3f} seconds") 
 
    step = total_frames // num_frames 
    frame_indices = [i * step for i in range(num_frames)] 
 
    os.makedirs(output_dir, exist_ok=True) 
    timestamps = [] 
 
    for idx, frame_no in enumerate(frame_indices): 
        cap.set(cv2.CAP_PROP_POS_FRAMES, frame_no) 
        ret, frame = cap.read() 
        if not ret: 
            print(f"Warning: Could not read frame {frame_no}") 
            continue 
 
        frame_filename = os.path.join(output_dir, f"frame_{idx+1}.jpg") 
        cv2.imwrite(frame_filename, frame) 
 
        timestamp_sec = frame_no / fps 
        timestamp = format_timestamp(timestamp_sec) 
        timestamps.append((frame_filename, timestamp)) 
 
    cap.release() 
    return timestamps 
 
# Example usage 
video_file = "videosummary01.mp4" 
output_folder = "extracted_frames" 
frame_data = extract_key_frames(video_file, output_folder, num_frames=5) 
 
print("\nExtracted Frame Timestamps:") 
for fname, ts in frame_data: 
    print(f"{fname} -> {ts}") 

Output: 

Video FPS: 25.08108108108108 

Total frames: 27 

Duration: 1.077 seconds 

 

Extracted Frame Timestamps: 

extracted_frames\frame_1.jpg -> 00:00:00.000 

extracted_frames\frame_2.jpg -> 00:00:00.199 

extracted_frames\frame_3.jpg -> 00:00:00.398 

extracted_frames\frame_4.jpg -> 00:00:00.598 

extracted_frames\frame_5.jpg -> 00:00:00.797