ffmpeg-format-conversion

# 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 ```bash # 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 ```bash # 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 ```bash # 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 ```bash # 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 ```bash # 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 ```bash # 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