Audio Conversion Examples
SwissKnife supports high-quality audio conversion between popular formats using FFmpeg.
MP3 to FLAC (Lossless)
Convert compressed MP3 to lossless FLAC format:
python solution.py convert song.mp3 lossless.flac
Converting: /path/to/song.mp3 to /path/to/lossless.flac
Success: Audio conversion successful: /path/to/lossless.flac
Info: Conversion completed in 3.21 seconds.
FLAC (Free Lossless Audio Codec) provides perfect audio quality preservation without compression artifacts, ideal for archiving or audiophile use.
WAV to AAC (Compression)
Compress uncompressed WAV files to efficient AAC format:
python solution.py convert podcast.wav compressed.aac
M4A to OGG
Convert Apple’s M4A format to open-source OGG Vorbis:
python solution.py convert recording.m4a universal.ogg
Video Conversion Examples
MP4 to WebM (Web Optimization)
Convert videos to WebM format optimized for web streaming:
python solution.py convert movie.mp4 optimized.webm
Converting: /path/to/movie.mp4 to /path/to/optimized.webm
Success: Video conversion successful: /path/to/optimized.webm
Info: Conversion completed in 45.67 seconds.
python solution.py convert presentation.avi portable.mov
MKV to GIF (Animation)
Create optimized GIF animations from video files:
python solution.py convert tutorial.mkv social.gif
GIF conversion automatically optimizes for social media: 480px width, 10 fps, optimized color palette. Perfect for short clips and demonstrations.
Audio Codec Settings
SwissKnife uses optimized codec settings for each audio format (from solution.py:76):
codec_map = {
".mp3": ("libmp3lame", "192k"), # MP3 with LAME encoder
".m4a": ("aac", "192k"), # AAC in M4A container
".aac": ("aac", "192k"), # AAC format
".wav": ("pcm_s16le", None), # Uncompressed PCM
".ogg": ("libvorbis", "192k"), # Vorbis in OGG container
".flac": ("flac", None) # Lossless FLAC
}
Audio Quality Levels
| Format | Codec | Bitrate | Quality | Use Case |
|---|
| FLAC | flac | Lossless | Perfect | Archival, audiophile |
| WAV | PCM | Uncompressed | Perfect | Professional audio |
| MP3 | libmp3lame | 192k | High | General music |
| AAC | aac | 192k | High | Streaming, podcasts |
| M4A | aac | 192k | High | Apple devices |
| OGG | libvorbis | 192k | High | Open-source preference |
Video Codec Settings
Video conversions use format-specific optimizations (from solution.py:80):
fmt_map = {
".webm": (
"libvpx-vp9", # VP9 video codec
["-crf", "30", "-b:v", "0"], # Quality settings
"libopus", # Opus audio codec
["-b:a", "128k"]
),
".mp4": (
"libx264", # H.264 video codec
["-crf", "23", "-preset", "ultrafast"],
"aac", # AAC audio codec
["-b:a", "128k"],
["-movflags", "+faststart"] # Fast start for streaming
)
}
Video Quality Parameters
CRF (Constant Rate Factor):
- Lower CRF = Higher quality, larger file size
- WebM uses CRF 30 for web optimization
- MP4/MKV/AVI/MOV use CRF 23 for balanced quality
Presets:
ultrafast - Fast encoding, larger files- Used for quick conversions and preview generation
Audio Bitrate:
- 128k for video files (sufficient for most content)
- 192k for audio-only files (higher quality)
GIF Creation from Video
GIF conversion uses a two-pass process for optimal quality (from solution.py:71-74):
python solution.py convert video.mp4 animation.gif
-
Palette Generation: Creates optimized color palette
fps=10 - 10 frames per secondscale=480:-1 - 480px width, proportional heightpalettegen=stats_mode=diff - Optimized for differences
-
GIF Encoding: Uses generated palette
paletteuse=dither=bayer:bayer_scale=5 - Bayer dithering- Results in smooth color transitions
GIF files can become very large. The 480px width and 10 fps limits keep file sizes manageable for social media and web use. For longer videos, consider using WebM instead.
# Convert all MP3s to FLAC
python solution.py batch-convert ./music ./flac_archive .mp3 .flac
# Convert all MP4 videos to WebM
python solution.py batch-convert ./videos ./web_videos .mp4 .webm
# Create GIFs from all video files
python solution.py batch-convert ./tutorials ./gifs .mkv .gif
- MP3 - Most compatible format
- WAV - Uncompressed, professional use
- FLAC - Lossless compression
- AAC - Modern, efficient compression
- OGG - Open-source, good compression
- M4A - Apple ecosystem
- MP4 - Universal compatibility
- AVI - Legacy format support
- MKV - High-quality container
- MOV - Apple QuickTime format
- WMV - Windows Media Video
- FLV - Flash Video (legacy)
- WebM - Modern web format
- GIF - Animated images (output only)
Best Practices
For Audio
Archive in lossless: Use FLAC or WAV for master copies, then convert to compressed formats as needed.
192k bitrate is the sweet spot: For MP3, AAC, and OGG, 192k provides excellent quality while keeping file sizes reasonable.
For Video
Use WebM for web: WebM provides better compression than MP4 for web streaming with similar quality.
MP4 for compatibility: When you need maximum device compatibility, use MP4 with H.264 codec.
Keep GIFs short: Due to large file sizes, limit GIFs to 5-10 seconds of content. Use the split command first if needed.
- Video conversion is slow: Expect 30-60 seconds per minute of video
- Audio conversion is fast: Most audio files convert in 2-5 seconds
- GIF creation takes time: Two-pass encoding means longer processing
- File sizes: Video conversions can produce large files (100MB+ for HD content)
Common Use Cases
1. Music Library Conversion
# Convert entire music library to FLAC for archival
python solution.py batch-convert ./Music ./FLAC_Archive .mp3 .flac
2. Podcast Production
# Convert WAV recordings to AAC for distribution
python solution.py convert raw_recording.wav episode_01.aac
# Create GIF from video for Twitter/Discord
python solution.py convert highlight.mp4 share.gif
4. Web Video Optimization
# Convert videos to WebM for website embedding
python solution.py batch-convert ./raw_videos ./optimized .mp4 .webm
5. Apple Ecosystem
# Convert audio to M4A for iTunes/Apple Music
python solution.py convert song.flac itunes.m4a
# Convert video to MOV for iMovie/Final Cut
python solution.py convert footage.mkv editable.mov