atxinsky/ffmpeg-usage

ffmpeg Usage

Overview

This Skill provides comprehensive video and audio processing capabilities using ffmpeg. It includes battle-tested commands and workflows for common multimedia tasks, platform-specific optimizations, and best practices for quality and file size management.

Version: 1.0.0 Requirements: ffmpeg >= 4.0, ffprobe (optional but recommended)

Claude should use this Skill whenever users mention video or audio processing tasks, format conversions, social media optimization, or multimedia editing.

When to Apply

Use this Skill when the user requests:

• Video format conversion (MP4, WebM, MOV, etc.)
• Resolution scaling or aspect ratio changes
• GIF creation from videos
• Audio extraction or format conversion
• Video editing (trim, merge, speed adjustment, rotation)
• Subtitle processing (burn-in, soft subs, extraction)
• Video compression or optimization
• Platform-specific formatting (YouTube, Instagram, TikTok, Twitter)
• Thumbnail or frame extraction
• Batch processing of video/audio files

Prerequisites

Before using this skill, ensure ffmpeg is installed:

# macOS
brew install ffmpeg

# Ubuntu/Debian
sudo apt-get install ffmpeg

# Windows (with Chocolatey)
choco install ffmpeg

Verify installation:

ffmpeg -version

Supported Operations

1. Format Conversion

Convert between video formats with optimized settings.

MP4 to WebM:

ffmpeg -i input.mp4 -c:v libvpx-vp9 -crf 30 -b:v 0 -c:a libopus output.webm

MOV to MP4:

ffmpeg -i input.mov -c:v libx264 -c:a aac -strict experimental output.mp4

Any to MP4 (universal compatibility):

ffmpeg -i input.* -c:v libx264 -preset medium -crf 23 -c:a aac -b:a 128k output.mp4

2. Resolution Adjustment

Resize videos while maintaining aspect ratio.

Scale to 720p:

ffmpeg -i input.mp4 -vf scale=-1:720 -c:a copy output_720p.mp4

Scale to 1080p:

ffmpeg -i input.mp4 -vf scale=-1:1080 -c:a copy output_1080p.mp4

Scale to specific width (auto height):

ffmpeg -i input.mp4 -vf scale=1280:-1 -c:a copy output.mp4

Scale with padding (letterbox):

ffmpeg -i input.mp4 -vf "scale=1920:1080:force_original_aspect_ratio=decrease,pad=1920:1080:(ow-iw)/2:(oh-ih)/2" output.mp4

3. GIF Creation

Create high-quality GIFs from videos with optimized file size.

Basic GIF (10 fps):

ffmpeg -i input.mp4 -vf "fps=10,scale=480:-1:flags=lanczos" output.gif

High-quality GIF with palette:

# Generate palette
ffmpeg -i input.mp4 -vf "fps=10,scale=480:-1:flags=lanczos,palettegen" palette.png

# Create GIF using palette
ffmpeg -i input.mp4 -i palette.png -filter_complex "fps=10,scale=480:-1:flags=lanczos[x];[x][1:v]paletteuse" output.gif

GIF from specific time range:

ffmpeg -ss 00:00:10 -t 5 -i input.mp4 -vf "fps=10,scale=480:-1:flags=lanczos,split[s0][s1];[s0]palettegen[p];[s1][p]paletteuse" output.gif

4. Audio Operations

Extract, convert, and manipulate audio streams.

Extract audio to MP3:

ffmpeg -i input.mp4 -vn -acodec libmp3lame -q:a 2 output.mp3

Extract audio to WAV:

ffmpeg -i input.mp4 -vn -acodec pcm_s16le -ar 44100 -ac 2 output.wav

Convert audio format:

ffmpeg -i input.wav -c:a aac -b:a 192k output.m4a

Add background music:

ffmpeg -i video.mp4 -i music.mp3 -c:v copy -c:a aac -map 0:v:0 -map 1:a:0 -shortest output.mp4

Mix audio (overlay):

ffmpeg -i video.mp4 -i music.mp3 -filter_complex "[0:a][1:a]amix=inputs=2:duration=first" -c:v copy output.mp4

5. Video Editing

Trim, concatenate, and modify videos.

Trim video:

# From 10s to 30s
ffmpeg -i input.mp4 -ss 00:00:10 -to 00:00:30 -c copy output.mp4

# Duration-based (10s starting from 5s)
ffmpeg -i input.mp4 -ss 00:00:05 -t 10 -c copy output.mp4

Concatenate videos:

Choose method based on format and compatibility:

Method 1: Concat Protocol (Preferred - No temporary files needed)

# For MPEG formats: .ts, .mpg, .mpeg, .mp3, .aac, etc.
# Direct concatenation without creating list file
ffmpeg -i "concat:file1.mp3|file2.mp3|file3.mp3" -c copy output.mp3
ffmpeg -i "concat:video1.ts|video2.ts|video3.ts" -c copy output.ts

# Works with: TS, MPEG-1, MPEG-2, MP3, AAC
# Does NOT work with: MP4, MOV, MKV (use Method 2 instead)

Method 2: Concat Demuxer (For MP4, MOV, MKV)

# Use process substitution to avoid temporary files
ffmpeg -f concat -safe 0 -i <(printf "file '%s'\n" video1.mp4 video2.mp4 video3.mp4) -c copy output.mp4

# If shell doesn't support process substitution:
printf "file '%s'\n" video1.mp4 video2.mp4 video3.mp4 > list.txt
ffmpeg -f concat -safe 0 -i list.txt -c copy output.mp4
rm list.txt

Method 3: Concat Filter (When re-encoding is acceptable)

# Use when videos have different codecs/resolutions
ffmpeg -i video1.mp4 -i video2.mp4 -i video3.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]" output.mp4

Format Decision Guide:

• .mp3, .aac, .ts, .mpg, .mpeg → Use concat protocol (Method 1)
• .mp4, .mov, .mkv → Use concat demuxer (Method 2)
• Different codecs/resolutions → Use concat filter (Method 3)

Speed up/slow down:

# 2x speed
ffmpeg -i input.mp4 -filter:v "setpts=0.5*PTS" -an output.mp4

# 0.5x speed (slow motion)
ffmpeg -i input.mp4 -filter:v "setpts=2.0*PTS" output.mp4

Rotate video:

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

# 180 degrees
ffmpeg -i input.mp4 -vf "transpose=2,transpose=2" output.mp4

6. Subtitle Processing

Add, extract, or burn subtitles.

Burn subtitles into video:

ffmpeg -i input.mp4 -vf subtitles=subtitles.srt output.mp4

Add soft subtitles:

ffmpeg -i input.mp4 -i subtitles.srt -c copy -c:s mov_text output.mp4

Extract subtitles:

ffmpeg -i input.mp4 -map 0:s:0 subtitles.srt

7. Thumbnail Extraction

Extract frames as images.

Single frame at specific time:

ffmpeg -i input.mp4 -ss 00:00:05 -vframes 1 thumbnail.jpg

Multiple thumbnails:

# One frame every 10 seconds
ffmpeg -i input.mp4 -vf fps=1/10 thumb%04d.jpg

# First 10 frames
ffmpeg -i input.mp4 -vframes 10 frame%04d.png

8. Compression & Optimization

Reduce file size while maintaining quality.

Compress video (balanced):

ffmpeg -i input.mp4 -c:v libx264 -crf 23 -preset medium -c:a aac -b:a 128k output.mp4

High compression (smaller file):

ffmpeg -i input.mp4 -c:v libx264 -crf 28 -preset veryslow -c:a aac -b:a 96k output.mp4

Compress for web:

ffmpeg -i input.mp4 -c:v libx264 -preset medium -crf 23 -movflags +faststart -c:a aac -b:a 128k output.mp4

Platform-Specific Presets

YouTube Optimization

ffmpeg -i input.mp4 \
  -c:v libx264 -preset slow -crf 18 \
  -c:a aac -b:a 192k \
  -pix_fmt yuv420p \
  -movflags +faststart \
  youtube.mp4

Instagram Story (9:16)

ffmpeg -i input.mp4 \
  -vf "scale=1080:1920:force_original_aspect_ratio=decrease,pad=1080:1920:(ow-iw)/2:(oh-ih)/2" \
  -c:v libx264 -preset medium -crf 23 \
  -c:a aac -b:a 128k \
  -t 15 \
  instagram_story.mp4

Twitter/X (16:9, max 2:20)

ffmpeg -i input.mp4 \
  -vf scale=1280:720 \
  -c:v libx264 -preset medium -crf 23 \
  -c:a aac -b:a 128k \
  -t 140 \
  twitter.mp4

TikTok (9:16)

ffmpeg -i input.mp4 \
  -vf "scale=1080:1920:force_original_aspect_ratio=decrease,pad=1080:1920:(ow-iw)/2:(oh-ih)/2" \
  -c:v libx264 -preset medium -crf 23 \
  -c:a aac -b:a 128k \
  -t 60 \
  tiktok.mp4

Common Use Cases

Screen Recording Optimization

# Reduce file size of screen recordings
ffmpeg -i screen_recording.mov \
  -c:v libx264 -preset medium -crf 23 \
  -vf "scale=1920:-1" \
  -c:a aac -b:a 128k \
  optimized.mp4

Batch Conversion

# Convert all MOV files to MP4
for i in *.mov; do
  ffmpeg -i "$i" -c:v libx264 -crf 23 -c:a aac "${i%.mov}.mp4"
done

Create Video from Images

# From image sequence
ffmpeg -framerate 30 -pattern_type glob -i '*.jpg' \
  -c:v libx264 -pix_fmt yuv420p \
  output.mp4

# Single image to video (5 seconds)
ffmpeg -loop 1 -i image.jpg -c:v libx264 -t 5 -pix_fmt yuv420p output.mp4

Best Practices

1. Always check input file first:

   ffmpeg -i input.mp4
   # Or use ffprobe for detailed info
   ffprobe -v quiet -print_format json -show_format -show_streams input.mp4
   

2. Use -c copy when possible to avoid re-encoding:

   ffmpeg -i input.mp4 -ss 00:01:00 -t 30 -c copy output.mp4
   

3. Preview before processing with -t flag:

   # Test on first 10 seconds
   ffmpeg -i input.mp4 -t 10 [other options] test.mp4
   

4. Use appropriate CRF values:

   • 18 = visually lossless
   • 23 = high quality (default)
   • 28 = acceptable quality, smaller file
   • Range: 0 (lossless) to 51 (worst quality)

5. Add -movflags +faststart for web videos:

   • Enables progressive playback
   • Moves metadata to beginning of file

Error Handling

When using this skill, always:

1. Verify input file exists and is readable
2. Check ffmpeg installation before processing
3. Validate output path is writable
4. Handle errors gracefully with appropriate messages
5. Show progress when processing large files

Guidelines for Claude

When a user requests video/audio processing:

1. Identify the task type from the request
2. Select appropriate command from this skill
3. Verify prerequisites (ffmpeg installed, input file exists)
4. Explain what the command does before executing
5. Execute the command with proper error handling
6. Verify the output was created successfully
7. Suggest optimizations if applicable

For complex workflows, break down into steps and explain each one.

For video concatenation: Use process substitution with printf when possible to avoid temporary files (see Method 2 in concatenate section). Fall back to temporary list.txt only if needed.

Examples

User: "Convert this MOV file to MP4" Response: Use the MOV to MP4 conversion command with H.264 codec

User: "Make a GIF from this video, but only 5 seconds starting at 10 seconds in" Response: Use GIF creation with time range specification

User: "I need to resize this 4K video to 1080p for web" Response: Combine resolution scaling with web optimization preset

User: "Extract the audio as MP3" Response: Use audio extraction command with MP3 codec

References

• FFmpeg Official Documentation: https://ffmpeg.org/documentation.html
• FFmpeg Wiki: https://trac.ffmpeg.org/wiki
• Supported Codecs: https://ffmpeg.org/ffmpeg-codecs.html
• Filter Documentation: https://ffmpeg.org/ffmpeg-filters.html