Splitting Videos into Separate Clips and Merging Them into a New Video Project

1. Video Splitting

In this lecture, we’ll focus on video splitting and merging clips using the MoviePy library. You’ll learn how to divide videos into parts and create full-fledged video projects from those pieces. Think of it as a programming-themed video breakfast in "Python-mix" style from your favorite tutorials.

Let’s start with how to divide a video into fragments. This can be useful in all sorts of situations: from creating demos for your latest scientific discoveries to slicing up all the moments when you wink during Zoom meetings.

Splitting Video by Time

Splitting a video into fragments is based on using the cut method in MoviePy. We can specify the start and end time intervals that we’re interested in.

from moviepy.editor import VideoFileClip

# Load the video
clip = VideoFileClip("input_video.mp4")

# Cut a fragment from 10 to 20 seconds
clip1 = clip.subclip(10, 20)

# Save the cut fragment
clip1.write_videofile("clip1.mp4")

This code cuts out a fragment between the 10th and 20th seconds of the original video. To save yourself time and disk space, make sure to specify the correct timestamps to avoid ending up with a "random" clip of your remote coffee break.

Slicing Video into Multiple Parts

You can slice a video into several parts and save them as separate clips for further merging.

Slicing Video into Three Parts

Let’s say we have a video that’s 30 seconds long, and we want to divide it into three equal fragments of 10 seconds each.

# Create three equal fragments
clip1 = video.subclip(0, 10)
clip2 = video.subclip(10, 20)
clip3 = video.subclip(20, 30)

# Save the fragments
clip1.write_videofile("clip_part1.mp4")
clip2.write_videofile("clip_part2.mp4")
clip3.write_videofile("clip_part3.mp4")

This code creates three video clips:

1. clip1 — from 0 to 10 seconds,
2. clip2 — from 10 to 20 seconds,
3. clip3 — from 20 to 30 seconds.

Each fragment is saved as a separate video file.

Cutting the Most Interesting Fragments

Sometimes, one fragment isn’t enough, and you need a whole bouquet of video flowers. We can create multiple such fragments and save them.

clip2 = clip.subclip(30, 40)
clip3 = clip.subclip(50, 60)

clip2.write_videofile("clip2.mp4")
clip3.write_videofile("clip3.mp4")

Now we have three fragments cut from the original video. It’s like building a puzzle, but in reverse.

2. Merging Clips

Once we’ve sliced the video, it’s time to put our video cloud back together, but in a new, revamped form. MoviePy has great options for merging multiple clips into one.

Creating Compilations from Video Clips

To merge clips, we use the concatenate_videoclips method. This method allows you to arrange clips one after the other in a specified sequence.

from moviepy.editor import concatenate_videoclips

# Merge clips into one
final_clip = concatenate_videoclips([clip1, clip2, clip3])

# Save the merged video
final_clip.write_videofile("final_video.mp4")

Now we’ve got a new video project that’s a collection of your best moments. Or random ones, if you forgot about the sequence.

Adding Audio While Merging Clips

When merging video clips, you can also add an audio track. For instance, if you have a music file or another audio clip, you can overlay it onto the merged video.

Merging Video Clips with an Audio Track

from moviepy.editor import AudioFileClip

# Create an audio clip
audio_clip = AudioFileClip("background_music.mp3")

# Add the audio clip to the merged video
final_clip_with_audio = final_clip.set_audio(audio_clip)
final_clip_with_audio.write_videofile("combined_with_audio.mp4")

Here:

• AudioFileClip("background_music.mp3") creates an audio clip from the music file.
• set_audio(audio_clip) adds the audio track to the merged video final_clip.

3. Transitions Between Clips

In MoviePy, transitions between clips are achieved using the CompositeVideoClip class and various effects. The key idea is to overlay one clip onto another using effects like transparency or shifting. Transitions often include changes in transparency or sliding frames so one clip smoothly transitions into another.

Fade Transition

Fade is one of the most popular transitions, where the first clip gradually disappears and the second clip gradually appears on the screen. This effect is created using the crossfadein() or crossfadeout() function.

Creating a Fade Transition Between Two Clips

from moviepy.editor import VideoFileClip, concatenate_videoclips

# Load two video clips
clip1 = VideoFileClip("clip1.mp4").subclip(0, 5)  # First clip for 5 seconds
clip2 = VideoFileClip("clip2.mp4").subclip(0, 5)  # Second clip for 5 seconds

# Apply fade effect
clip1 = clip1.crossfadeout(1)  # Fade out clip 1 over 1 second
clip2 = clip2.crossfadein(1)   # Fade in clip 2 over 1 second

# Merge clips with transition
final_clip = concatenate_videoclips([clip1, clip2], method="compose")
final_clip.write_videofile("fade_transition.mp4")

In this example:

• crossfadeout(1) gradually makes the first clip less transparent over one second.
• crossfadein(1) gradually makes the second clip more transparent over one second.
• concatenate_videoclips([clip1, clip2], method="compose") merges the two clips with the fade transition.

Fade to Black Transition

The fade to black effect involves one clip fading to a black screen, followed by the next clip emerging from the black screen. This transition creates a sense of one scene ending before the next begins.

from moviepy.editor import VideoFileClip, concatenate_videoclips

# Load two clips
clip1 = VideoFileClip("clip1.mp4").subclip(0, 5)
clip2 = VideoFileClip("clip2.mp4").subclip(0, 5)

# Apply fade to black
clip1 = clip1.fadeout(1)  # Clip 1 fades to black
clip2 = clip2.fadein(1)   # Clip 2 fades in from black

# Merge clips with fade to black
final_clip = concatenate_videoclips([clip1, clip2], method="compose")
final_clip.write_videofile("fade_to_black_transition.mp4")

Here:

• fadeout(1) fades the clip to a black screen over one second.
• fadein(1) makes the second clip smoothly emerge from the black screen.

Now your video isn’t just a collection of clips but a real hit with smooth transitions. As you can see, we added fade-in and fade-out effects to make the video more polished.

4. Practical Use

The skills gained in this lecture are incredibly useful. Imagine you’re creating a programming tutorial, an ad for a new library, or editing your cat’s birth into the IT world (yes, that’s a thing!). Knowing how to slice videos and merge them into thematic blocks is a step toward becoming a real pro at video editing and automation.

Common Mistakes

When working with slicing and merging videos, be cautious with timestamps. We’ve all seen those moments when a video suddenly cuts off (and those boring conference slides start over). Make sure your timestamps are correct, and there are no mistakes. MoviePy might sometimes complain about incorrect formats or empty clips, so double-check your code for correctness before running it.

Hopefully, now you’re not just armed with knowledge but also excited about the possibilities that lie ahead. Dive into the world of video editing and creative solutions with Python and MoviePy!