Recording video in Raspberry Pi

Introduction

Recording video lets you capture moving images and sound to save memories or monitor places.

You want to make a short movie with your Raspberry Pi camera.

You need to record a time-lapse of a plant growing.

You want to monitor your home or garden with video.

You are making a project that needs video input for analysis.

Syntax

Raspberry Pi

import picamera
import time

with picamera.PiCamera() as camera:
    camera.start_recording('video.h264')
    time.sleep(10)  # record for 10 seconds
    camera.stop_recording()

Use picamera library to control the Raspberry Pi camera.

start_recording() begins saving video to a file.

Examples

This records a 5-second video and saves it as my_video.h264.

Raspberry Pi

import picamera

with picamera.PiCamera() as camera:
    camera.start_recording('my_video.h264')
    camera.wait_recording(5)  # record for 5 seconds
    camera.stop_recording()

This records video in 3 parts of 2 seconds each, printing progress.

Raspberry Pi

import picamera
import time

with picamera.PiCamera() as camera:
    camera.start_recording('timelapse.h264')
    for i in range(3):
        camera.wait_recording(2)  # record 2 seconds
        print(f'Captured {i+1} segments')
    camera.stop_recording()

Sample Program

This program records a 3-second video and saves it. It prints messages before and after recording.

Raspberry Pi

import picamera
import time

with picamera.PiCamera() as camera:
    print('Starting video recording for 3 seconds...')
    camera.start_recording('test_video.h264')
    time.sleep(3)
    camera.stop_recording()
    print('Recording stopped. Video saved as test_video.h264')

Important Notes

Make sure your Raspberry Pi camera is enabled in settings before running the code.

The video file is saved in .h264 format, which can be played with VLC or converted to MP4.

Use time.sleep() or camera.wait_recording() to control how long to record.

Summary

Use the picamera library to record video on Raspberry Pi.

Start recording with start_recording() and stop with stop_recording().

Control recording length with time.sleep() or wait_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