FFMPEG 101 - A Beginner's Guide to Video Editing with FFMPEG

Introduction

FFMPEG is the foundation of video editing and processing. It's a command-line tool that allows you to manipulate, convert, and stream multimedia files, enabling you to create captivating videos and audio files.

Today, we're going to delve into the world of FFMPEG.

What is FFMPEG and Why Use It?

FFMPEG (Fast Forward MPEG) is a complete, cross-platform solution for recording, converting, and streaming audio and video. It's the Swiss Army knife of multimedia processing, offering:

Format conversion between virtually any media formats
High-performance video and audio processing
Command-line interface for automation and scripting
Free and open-source software with regular updates
Extensive codec support for various multimedia formats

Installing FFMPEG

Here's how to install FFMPEG on macOS:

brew install ffmpeg

Basic FFMPEG Commands and Syntax

The basic syntax for FFMPEG commands follows this pattern:

ffmpeg [global_options] {[input_options] -i input_url} ... {[output_options] output_url} ...

# - `-i`: Input file
# - `-c`: Codec selection
# - `-f`: Force format
# - `-y`: Overwrite output files without asking

Common Video Editing Tasks

Snapping Screenshots

# Take first frame as screenshot
ffmpeg -i input.mp4 -f image2 output.png
# Take a screenshot every 5 seconds
ffmpeg -i input.mp4 -f image2 -vf fps=1/5 output-%03d.png

Cutting and Trimming Videos

# Cut video from 00:00:30 to 00:02:00
ffmpeg -i input.mp4 -ss 00:00:30 -to 00:02:00 -c copy output.mp4

Merging Multiple Videos

# Create a file containing video paths
echo "file 'video1.mp4'" > videos.txt
echo "file 'video2.mp4'" >> videos.txt

# Concatenate videos
ffmpeg -f concat -safe 0 -i videos.txt -c copy output.mp4

Converting Video Formats

# Convert MP4 to WebM
ffmpeg -i input.mp4 output.webm

# Convert with specific codec
ffmpeg -i input.mp4 -c:v libx264 -c:a aac output.mp4

Adjusting Video Quality and Bitrate

# Set specific bitrate (2Mbps)
ffmpeg -i input.mp4 -b:v 2M output.mp4

# Use CRF for quality-based encoding (18-28 is good range)
ffmpeg -i input.mp4 -c:v libx264 -crf 23 output.mp4

Audio Manipulation with FFMPEG

Extract Audio from Video

ffmpeg -i video.mp4 -vn -acodec mp3 audio.mp3

Change Audio Volume

# Increase volume by 2x
ffmpeg -i input.mp4 -filter:a "volume=2.0" output.mp4

Adding Filters and Effects

Basic Video Filters

# Resize video to 720p
ffmpeg -i input.mp4 -vf scale=-1:720 output.mp4

# Rotate video 90 degrees
ffmpeg -i input.mp4 -vf "transpose=1" output.mp4

Multiple Filters

# Apply multiple filters
ffmpeg -i input.mp4 -vf "scale=1280:720,setsar=1:1" output.mp4

Handling Subtitles and Metadata

Add Subtitles

# Hardcode subtitles into video
ffmpeg -i input.mp4 -vf subtitles=subs.srt output.mp4

Modify Metadata

# Add title metadata
ffmpeg -i input.mp4 -metadata title="My Video" output.mp4

Streaming with FFMPEG

Stream to RTMP Server

ffmpeg -i input.mp4 -c:v libx264 -c:a aac -f flv rtmp://server/live/stream_key

Advanced Techniques and Tips

Use Hardware Acceleration

# Use NVIDIA GPU acceleration
ffmpeg -hwaccel cuda -i input.mp4 -c:v h264_nvenc output.mp4

Create Thumbnails

# Extract one frame every second
ffmpeg -i input.mp4 -vf fps=1 thumb%d.jpg

Add Watermark

ffmpeg -i input.mp4 -i watermark.png -filter_complex "overlay=10:10" output.mp4

Combining Separate Video and Audio Files

Sometimes you need to combine a video file with a separate audio file. Here's how to do it:

Basic Combination

# Combine video.mp4 with audio.mp3
ffmpeg -i video.mp4 -i audio.mp3 -c:v copy -c:a aac output.mp4

Combining with Specific Segments

If you want to use specific segments from both files:

# Take video segment (30s-120s) from video.mp4 and audio segment (90s-180s) from audio.mp3
ffmpeg -i video.mp4 -i audio.mp3 -filter_complex \
"[0:v]trim=start=30:end=120,setpts=PTS-STARTPTS[v]; \
 [1:a]atrim=start=90:end=180,asetpts=PTS-STARTPTS[a]" \
-map "[v]" -map "[a]" output.mp4

Let's break down what this command does:

-i video.mp4 -i audio.mp3 - Input both files (video is input 0, audio is input 1)
[0:v]trim=start=30:end=120 - Takes segment from the video file (30s to 120s)
[1:a]atrim=start=90:end=180 - Takes segment from the audio file (90s to 180s)
-map "[v]" -map "[a]" - Combines the processed video and audio streams

Note:

Use [0:v] for the first input's video stream
Use [1:a] for the second input's audio stream
Times are in seconds (90 = 1:30 minutes, 120 = 2 minutes, etc.)

Splitting Videos

Split by Frame Numbers

To split a video into segments based on specific frame numbers:

# Split video into segments of 500 frames each
ffmpeg -i input.mp4 \
  -vf select='between(n\,0\,499)' -c:v libx264 -c:a aac output_0_499.mp4 \
  -vf select='between(n\,500\,999)' -c:v libx264 -c:a aac output_500_999.mp4 \
  -vf select='between(n\,1000\,1499)' -c:v libx264 -c:a aac output_1000_1499.mp4

You can also create a script to automate this for any number of segments:

#!/bin/bash
input_file="input.mp4"
frames_per_segment=500

# Get total number of frames
total_frames=$(ffprobe -v error -select_streams v:0 -count_packets \
  -show_entries stream=nb_read_packets -of csv=p=0 "$input_file")

# Split into segments
for ((start=0; start<total_frames; start+=frames_per_segment)); do
  end=$((start + frames_per_segment - 1))
  ffmpeg -i "$input_file" \
    -vf select="between(n\,$start\,$end)" \
    -c:v libx264 -c:a aac \
    "output_${start}_${end}.mp4"
done

Note:

n represents the frame number in the select filter
Use \ before commas in the select filter to escape them
The -c:v libx264 and -c:a aac ensure high-quality output

Real-World Examples

# Convert video for Instagram (square format, max 60s)
ffmpeg -i input.mp4 -t 60 -vf "scale=1080:1080:force_original_aspect_ratio=decrease,pad=1080:1080:(ow-iw)/2:(oh-ih)/2" -c:v libx264 -crf 23 -c:a aac -b:a 128k instagram_ready.mp4

Example 2: Preparing Video for Web Streaming

# Create adaptive bitrate streams
ffmpeg -i input.mp4 \
  -vf scale=w=1280:h=720 -c:v libx264 -b:v 2800k -c:a aac -b:a 128k 720p.mp4 \
  -vf scale=w=854:h=480 -c:v libx264 -b:v 1400k -c:a aac -b:a 128k 480p.mp4 \
  -vf scale=w=640:h=360 -c:v libx264 -b:v 800k -c:a aac -b:a 96k 360p.mp4

Example 3: Video Podcast Processing

# Enhance audio and add intro/outro
ffmpeg -i intro.mp4 -i main.mp4 -i outro.mp4 \
  -filter_complex "[0:v][0:a][1:v][1:a][2:v][2:a]concat=n=3:v=1:a=1[v][a]" \
  -map "[v]" -map "[a]" \
  -af "compand=attacks=0:points=-80/-80|-45/-15|-27/-9|0/-7|20/-7:gain=5" \
  podcast_final.mp4

Visual Guide to FFMPEG Filters

Filter Graph Visualization

Input -> [Scale] -> [Crop] -> [Overlay] -> Output
            ↓         ↓          ↑
         Width     Remove    Add Logo
         Height    Edges      Image

Common Filter Combinations

# Picture-in-picture effect
ffmpeg -i main.mp4 -i overlay.mp4 -filter_complex "[0:v][1:v]overlay=W-w-10:H-h-10:enable='between(t,0,20)'" output.mp4

# Split screen effect
ffmpeg -i left.mp4 -i right.mp4 -filter_complex "[0:v]pad=iw*2:ih[bg]; [bg][1:v]overlay=w" output.mp4

Advanced Use Cases

Video Analytics

# Extract scene changes
ffmpeg -i input.mp4 -vf "select=gt(scene\,0.4),showinfo" -f null - 2> scenes.txt

# Generate video thumbnails at scene changes
ffmpeg -i input.mp4 -vf "select=gt(scene\,0.4),scale=320:180" -vsync vfr thumbs_%d.jpg

Live Streaming Setup

# Stream desktop with webcam overlay
ffmpeg -f avfoundation -i "1:0" -f avfoundation -i "0" \
  -filter_complex "[1:v]scale=320:-1[cam];[0:v][cam]overlay=main_w-overlay_w-10:main_h-overlay_h-10" \
  -c:v libx264 -preset veryfast -maxrate 3000k -bufsize 6000k \
  -pix_fmt yuv420p -g 50 -c:a aac -b:a 128k -ar 44100 \
  -f flv rtmp://live-server/stream

Best Practices

1. Quality Optimization

Use two-pass encoding for optimal quality/size ratio:

ffmpeg -i input.mp4 -c:v libx264 -b:v 2M -pass 1 -f null /dev/null && \
ffmpeg -i input.mp4 -c:v libx264 -b:v 2M -pass 2 output.mp4

2. Performance Optimization

Use hardware acceleration when available
Implement parallel processing for batch operations:

# Process multiple files in parallel
for file in *.mp4; do
    ffmpeg -i "$file" -c:v libx264 -preset medium "compressed_${file}" &
done
wait

3. Error Handling

Always validate input files:

ffmpeg -v error -i input.mp4 -f null - 2>error.log

4. Resource Management

Monitor system resources:

# Limit CPU usage
ffmpeg -i input.mp4 -threads 4 output.mp4

Workflow Automation

Batch Processing Script

#!/bin/bash
# Example script for batch processing videos
for input in *.mp4; do
    # Create output filename
    output="processed_${input}"
    
    # Process video with standard settings
    ffmpeg -i "$input" \
        -c:v libx264 -preset medium -crf 23 \
        -c:a aac -b:a 128k \
        -movflags +faststart \
        "$output"
done

Quality Control Checks

# Check video quality metrics
ffmpeg -i input.mp4 -filter:v "signalstats" -f null - 2>&1 | grep "YAVG"

# Validate audio levels
ffmpeg -i input.mp4 -filter:a "volumedetect" -f null - 2>&1 | grep "max_volume"

Troubleshooting Guide

Common Issues and Solutions

Sync Issues

# Fix audio/video sync
ffmpeg -i input.mp4 -c copy -fflags +genpts output.mp4

Memory Problems

# Reduce memory usage
ffmpeg -i input.mp4 -c:v libx264 -preset ultrafast output.mp4

Speed Optimization

# Fast encoding with reasonable quality
ffmpeg -i input.mp4 -c:v libx264 -preset veryfast -crf 23 output.mp4

Remember to always test your commands with a small sample before processing large files or batches. This practice will save you time and prevent potential issues with your final output.

For more advanced techniques and detailed documentation, visit the official FFMPEG documentation and join the active FFMPEG community on GitHub.

Conclusion

FFMPEG is an incredibly powerful tool that can handle almost any multimedia processing task. While the command-line interface might seem daunting at first, its flexibility and automation capabilities make it an invaluable tool for video editing and processing. Start with basic commands and gradually explore more advanced features as you become comfortable with the syntax and options.

Remember to always keep a backup of your original files and test your commands with small samples before processing large files. With practice, you'll find FFMPEG to be an indispensable tool in your multimedia workflow.

For more information and detailed documentation, visit the official FFMPEG documentation.

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