Recording video in Raspberry Pi - Mini Project: Build & Apply

Recording video

📖 Scenario: You have a Raspberry Pi with a camera module attached. You want to record a short video using Python code on your Raspberry Pi.

🎯 Goal: Write a Python program that records a 5-second video using the Raspberry Pi camera and saves it as my_video.h264.

📋 What You'll Learn

Create a PiCamera object

Set the video resolution to 640x480

Record a 5-second video and save it as my_video.h264

Print a message when recording starts and ends

💡 Why This Matters

🌍 Real World

Recording videos on a Raspberry Pi is useful for security cameras, time-lapse projects, or capturing events automatically.

💼 Career

Understanding how to control hardware like cameras programmatically is important for roles in embedded systems, IoT development, and robotics.

1

Setup the camera object

Import PiCamera from picamera and create a camera object called camera.

Raspberry Pi

# Import PiCamera and create camera object
# Your code here

Hint

Use from picamera import PiCamera to import the camera class.

2

Configure the camera resolution

Set the resolution property of the camera object to (640, 480).

Raspberry Pi

from picamera import PiCamera
camera = PiCamera()
# Set camera resolution to 640x480
# Your code here

Hint

Use camera.resolution = (640, 480) to set the video size.

3

Record a 5-second video

Use camera.start_recording('my_video.h264') to start recording, then wait 5 seconds using camera.wait_recording(5), and finally stop recording with camera.stop_recording().

Raspberry Pi

from picamera import PiCamera
camera = PiCamera()
camera.resolution = (640, 480)
# Start recording, wait 5 seconds, then stop recording
# Your code here

Hint

Use start_recording, wait_recording, and stop_recording methods in order.

4

Print messages before and after recording

Add print('Recording started') before starting the recording and print('Recording stopped') after stopping the recording.

Raspberry Pi

from picamera import PiCamera
camera = PiCamera()
camera.resolution = (640, 480)
# Print message before recording
# Your code here
camera.start_recording('my_video.h264')
camera.wait_recording(5)
camera.stop_recording()
# Print message after recording
# Your code here

Hint

Use two print statements: one before start_recording and one after stop_recording.

Practice

1. What is the main function of start_recording() in the picamera library on Raspberry Pi?

easy

A. To pause the video recording

B. To stop the video recording

C. To begin capturing video and save it to a file

D. To preview the camera feed without recording

Solution

1. Step 1: Understand the purpose of start_recording()

   This function initiates the process of capturing video from the camera and saving it to a specified file.

2. Step 2: Differentiate from other functions

   stop_recording() ends the recording, while start_recording() begins it. Previewing is done by start_preview().

3. Final Answer:

   To begin capturing video and save it to a file -> Option C

4. Quick Check:

   start_recording() starts video capture [OK]

Hint: Remember: start_recording() means begin saving video [OK]

Common Mistakes:

• Confusing start_recording() with stop_recording()
• Thinking start_recording() previews video
• Assuming it pauses recording

2. Which of the following is the correct way to stop a video recording using the picamera library?

easy

A. camera.stop()

B. camera.stop_recording()

C. camera.end_recording()

D. camera.finish_recording()

Solution

1. Step 1: Recall the method to stop recording

   The picamera library uses stop_recording() to end video capture.

2. Step 2: Verify method names

   Other options like stop(), end_recording(), or finish_recording() are not valid methods in picamera.

3. Final Answer:

   camera.stop_recording() -> Option B

4. Quick Check:

   Use stop_recording() to end video [OK]

Hint: Stop recording always uses stop_recording() [OK]

Common Mistakes:

• Using stop() instead of stop_recording()
• Confusing method names
• Assuming end_recording() exists

3. What will be the output behavior of this code snippet on Raspberry Pi?

import time
from picamera import PiCamera
camera = PiCamera()
camera.start_recording('video.h264')
time.sleep(5)
camera.stop_recording()

medium

A. Records a 5-second video and saves it as 'video.h264'

B. Records video indefinitely until manually stopped

C. Throws an error because of missing preview

D. Records video but does not save to file

Solution

1. Step 1: Analyze the code flow

   The code starts recording, waits 5 seconds, then stops recording.

2. Step 2: Understand the effect of time.sleep(5)

   This pauses the program for 5 seconds while recording continues, so the video length is 5 seconds.

3. Final Answer:

   Records a 5-second video and saves it as 'video.h264' -> Option A

4. Quick Check:

   sleep(5) controls recording length [OK]

Hint: sleep() pauses recording duration exactly [OK]

Common Mistakes:

• Thinking recording stops immediately
• Assuming preview is required to record
• Believing video is not saved without explicit save

4. Identify the error in this code snippet for recording video on Raspberry Pi:

from picamera import PiCamera
import time
camera = PiCamera()
camera.start_recording('video.h264')
time.wait(3)
camera.stop_recording()

medium

A. stop_recording() should be called before start_recording()

B. Missing camera initialization

C. File name must be .mp4 not .h264

D. Incorrect method name 'time.wait' instead of 'time.sleep'

Solution

1. Step 1: Check the time delay function

   The code uses time.wait(3), but the correct function to pause is time.sleep(3).

2. Step 2: Confirm other parts are correct

   Camera is initialized, start and stop recording are in correct order, and .h264 is a valid format.

3. Final Answer:

   Incorrect method name 'time.wait' instead of 'time.sleep' -> Option D

4. Quick Check:

   Use sleep() to pause, not wait() [OK]

Hint: Use time.sleep() to pause, not time.wait() [OK]

Common Mistakes:

• Using time.wait() instead of time.sleep()
• Thinking .h264 is invalid file extension
• Calling stop_recording() before start_recording()

5. You want to record a video on Raspberry Pi that automatically stops after 10 seconds without using time.sleep(). Which method should you use to control recording duration?

hard

A. Use camera.wait_recording(10) after start_recording()

B. Use time.sleep(10) before start_recording()

C. Call stop_recording() immediately after start_recording()

D. Use camera.record_for(10) method

Solution

1. Step 1: Understand wait_recording() usage

   This method pauses the program while continuing recording, allowing precise control without blocking the whole program.

2. Step 2: Compare with other options

   time.sleep(10) pauses the entire program, stop_recording() immediately stops recording, and record_for() does not exist.

3. Final Answer:

   Use camera.wait_recording(10) after start_recording() -> Option A

4. Quick Check:

   wait_recording() controls duration without sleep [OK]

Hint: Use wait_recording() to record timed video without sleep [OK]

Common Mistakes:

• Using sleep() which blocks whole program
• Calling stop_recording() too soon
• Assuming record_for() method exists