When working with video processing in Python, it can be useful to add telemetry data to the video. Telemetry data can include information such as the frame rate, timestamp, or any other relevant data that can provide additional context to the video. In this article, we will explore three different ways to add telemetry data to a video in Python.

Option 1: Using OpenCV

OpenCV is a popular library for computer vision tasks in Python. It provides various functions and methods to manipulate and process videos. To add telemetry data to a video using OpenCV, we can utilize the `cv2.putText()` function to overlay text on each frame of the video.

import cv2

def add_telemetry_data(video_path):
    cap = cv2.VideoCapture(video_path)
    fps = cap.get(cv2.CAP_PROP_FPS)
    frame_count = int(cap.get(cv2.CAP_PROP_FRAME_COUNT))

    for frame_number in range(frame_count):
        ret, frame = cap.read()
        if not ret:
            break

        # Add telemetry data to the frame
        telemetry_text = f"Frame: {frame_number} - FPS: {fps}"
        cv2.putText(frame, telemetry_text, (10, 30), cv2.FONT_HERSHEY_SIMPLEX, 1, (0, 255, 0), 2)

        # Display the frame
        cv2.imshow('Telemetry Video', frame)
        if cv2.waitKey(1) & 0xFF == ord('q'):
            break

    cap.release()
    cv2.destroyAllWindows()

video_path = 'path/to/video.mp4'
add_telemetry_data(video_path)

This code snippet reads the video using `cv2.VideoCapture()`, retrieves the frame rate using `cap.get(cv2.CAP_PROP_FPS)`, and the total number of frames using `cap.get(cv2.CAP_PROP_FRAME_COUNT)`. Then, it iterates over each frame, adds the telemetry data using `cv2.putText()`, and displays the frame with the telemetry data using `cv2.imshow()`. Pressing ‘q’ will exit the video playback.

Option 2: Using MoviePy

MoviePy is a Python library that provides a high-level interface for video editing tasks. It is built on top of the popular FFmpeg library. To add telemetry data to a video using MoviePy, we can utilize the `TextClip` class to create a text clip with the telemetry data and then overlay it on the video using the `CompositeVideoClip` class.

from moviepy.editor import VideoFileClip, TextClip, CompositeVideoClip

def add_telemetry_data(video_path):
    video = VideoFileClip(video_path)
    fps = video.fps
    frame_count = video.reader.nframes

    def add_telemetry_text(get_frame, t):
        frame = get_frame(t)

        # Add telemetry data to the frame
        telemetry_text = f"Frame: {int(t * fps)} - FPS: {fps}"
        text_clip = TextClip(telemetry_text, fontsize=30, color='green', font='Arial', bg_color='transparent')
        text_clip = text_clip.set_position(('left', 'top')).set_duration(1 / fps)
        frame_with_telemetry = CompositeVideoClip([frame, text_clip])

        return frame_with_telemetry

    video_with_telemetry = video.fl(add_telemetry_text)
    video_with_telemetry.write_videofile('output.mp4', codec='libx264')

video_path = 'path/to/video.mp4'
add_telemetry_data(video_path)

This code snippet uses `VideoFileClip` to load the video, retrieves the frame rate using `video.fps`, and the total number of frames using `video.reader.nframes`. Then, it defines a function `add_telemetry_text` that takes a time parameter `t` and returns a frame with the telemetry data overlay. The telemetry data is added using `TextClip` and then composited with the original frame using `CompositeVideoClip`. Finally, the video with telemetry data is saved using `write_videofile()`.

Option 3: Using Pygame

Pygame is a popular library for game development in Python. It provides various functionalities for working with multimedia, including video playback. To add telemetry data to a video using Pygame, we can utilize the `pygame.font` module to render text on each frame of the video.

import pygame
import cv2

def add_telemetry_data(video_path):
    pygame.init()
    clock = pygame.time.Clock()

    cap = cv2.VideoCapture(video_path)
    fps = cap.get(cv2.CAP_PROP_FPS)
    frame_count = int(cap.get(cv2.CAP_PROP_FRAME_COUNT))

    screen_width = int(cap.get(cv2.CAP_PROP_FRAME_WIDTH))
    screen_height = int(cap.get(cv2.CAP_PROP_FRAME_HEIGHT))
    screen = pygame.display.set_mode((screen_width, screen_height))

    font = pygame.font.SysFont('Arial', 30)

    for frame_number in range(frame_count):
        ret, frame = cap.read()
        if not ret:
            break

        # Add telemetry data to the frame
        telemetry_text = f"Frame: {frame_number} - FPS: {fps}"
        text_surface = font.render(telemetry_text, True, (0, 255, 0))
        screen.blit(text_surface, (10, 10))

        # Display the frame
        pygame.surfarray.blit_array(screen, frame)
        pygame.display.flip()
        clock.tick(fps)

    cap.release()
    pygame.quit()

video_path = 'path/to/video.mp4'
add_telemetry_data(video_path)

This code snippet initializes Pygame, creates a Pygame screen with the same dimensions as the video, and sets up a clock for frame rate control. It then reads the video using `cv2.VideoCapture()`, retrieves the frame rate using `cap.get(cv2.CAP_PROP_FPS)`, and the total number of frames using `cap.get(cv2.CAP_PROP_FRAME_COUNT)`. The telemetry data is added to each frame using `pygame.font.render()` and displayed on the screen using `screen.blit()`. Finally, the frame is displayed using `pygame.display.flip()` and the frame rate is controlled using `clock.tick()`.

Among the three options, Option 2 using MoviePy provides a higher-level interface and simplifies the process of adding telemetry data to a video. It abstracts away some of the low-level details and provides a more concise and readable code. Therefore, Option 2 is the recommended approach for adding telemetry data to a video in Python.