OpenSkillIndex← back to search
claude-code

Skillsbench FFmpeg Format Conversion

Convert media files between formats - video containers, audio formats, and codec transcoding

install
source · Clone the upstream repo
git clone https://github.com/benchflow-ai/skillsbench
Claude Code · Install into ~/.claude/skills/
T=$(mktemp -d) && git clone --depth=1 https://github.com/benchflow-ai/skillsbench "$T" && mkdir -p ~/.claude/skills && cp -r "$T/tasks/multilingual-video-dubbing/environment/skills/ffmpeg-format-conversion" ~/.claude/skills/benchflow-ai-skillsbench-ffmpeg-format-conversion && rm -rf "$T"
manifest: tasks/multilingual-video-dubbing/environment/skills/ffmpeg-format-conversion/SKILL.md
source content

FFmpeg Format Conversion Skill

Convert media files between different formats and containers.

When to Use

  • Convert video containers (MP4, MKV, AVI, etc.)
  • Convert audio formats (MP3, AAC, WAV, etc.)
  • Transcode to different codecs
  • Copy streams without re-encoding (fast)

Basic Conversion

# Convert container format (re-encode)
ffmpeg -i input.avi output.mp4

# Copy streams without re-encoding (fast, no quality loss)
ffmpeg -i input.mp4 -c copy output.mkv

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

Video Codec Conversion

# H.264
ffmpeg -i input.mp4 -c:v libx264 output.mp4

# H.265 (better compression)
ffmpeg -i input.mp4 -c:v libx265 output.mp4

# VP9 (web optimized)
ffmpeg -i input.mp4 -c:v libvpx-vp9 output.webm

# AV1 (modern codec)
ffmpeg -i input.mp4 -c:v libaom-av1 output.mp4

Audio Format Conversion

# MP3
ffmpeg -i input.wav -acodec libmp3lame -q:a 2 output.mp3

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

# Opus (best quality/bitrate)
ffmpeg -i input.wav -c:a libopus -b:a 128k output.opus

# FLAC (lossless)
ffmpeg -i input.wav -c:a flac output.flac

Quality Settings

# CRF (Constant Rate Factor) - lower is better quality
ffmpeg -i input.mp4 -c:v libx264 -crf 23 output.mp4

# Bitrate
ffmpeg -i input.mp4 -b:v 2M -b:a 192k output.mp4

# Two-pass encoding (best quality)
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

Presets

# Encoding speed presets (faster = larger file)
ffmpeg -i input.mp4 -c:v libx264 -preset fast output.mp4
# Options: ultrafast, superfast, veryfast, faster, fast, medium, slow, slower, veryslow

# Quality presets
ffmpeg -i input.mp4 -c:v libx264 -preset slow -crf 18 output.mp4

Batch Conversion

# Convert all MKV to MP4
for f in *.mkv; do
  ffmpeg -i "$f" -c copy "${f%.mkv}.mp4"
done

# Convert with re-encoding
for f in *.avi; do
  ffmpeg -i "$f" -c:v libx264 -c:a aac "${f%.avi}.mp4"
done

Common Codecs

Video

  • H.264 (libx264) - Universal compatibility
  • H.265 (libx265) - Better compression
  • VP9 (libvpx-vp9) - Open standard
  • AV1 (libaom-av1) - Modern codec

Audio

  • AAC (aac) - Universal
  • MP3 (libmp3lame) - Legacy
  • Opus (libopus) - Best quality/bitrate
  • FLAC (flac) - Lossless

Notes

  • Use 
    -c copy
    when possible for speed (no re-encoding)
  • Re-encoding is slower but allows codec/quality changes
  • CRF 18-23 is good quality range for H.264
  • Preset affects encoding speed vs file size tradeoff