The Compression Challenge
Video files can be massive. A 10-minute 4K video can easily exceed 5GB. But with the right techniques, you can reduce file size by 50-80% with minimal quality loss.
Understanding Video Compression
Video compression works by removing redundant information:
- Spatial compression - Removes redundancy within frames
- Temporal compression - Removes redundancy between frames
- Perceptual compression - Removes details humans can't perceive
Key Settings for Quality Compression
1. CRF (Constant Rate Factor)
CRF controls the quality-vs-size tradeoff. Lower values mean better quality:
| CRF Value | Quality | Use Case |
|---|---|---|
| 18-20 | Near-lossless | Archiving |
| 21-23 | High quality | General use |
| 24-26 | Good quality | Web sharing |
| 27-30 | Acceptable | Quick previews |
Recommendation: Start with CRF 23 and adjust based on results.
2. Resolution
Reducing resolution is the most effective way to reduce file size:
| Resolution | Typical Use | Size Reduction |
|---|---|---|
| 4K (2160p) | Original | Baseline |
| 1080p | HD viewing | 75% smaller |
| 720p | Mobile/web | 85% smaller |
| 480p | Thumbnail | 95% smaller |
Tip: Most viewers can't distinguish 4K from 1080p on typical screens.
3. Frame Rate
Films use 24fps while games often use 60fps. Match your content:
- 24fps - Cinematic look, smaller files
- 30fps - Standard video, balanced
- 60fps - Sports, gaming, smooth motion
4. Audio Bitrate
Audio often takes 10-20% of file size. Optimize it:
- 320kbps - Audiophile quality
- 192kbps - High quality
- 128kbps - Standard quality
- 96kbps - Acceptable for speech
Compression Workflow
Step 1: Analyze Your Video
Check current specs:
- Resolution and aspect ratio
- Frame rate
- Current bitrate
- Audio channels
Step 2: Choose Target Settings
Based on your delivery platform:
For YouTube/Social Media:
- 1080p, 30fps, CRF 23
- H.264 codec for compatibility
- AAC audio at 128kbps
For Website Embed:
- 720p, 30fps, CRF 26
- VP9 codec for WebM
- Opus audio at 96kbps
For Email/Messaging:
- 720p, 24fps, CRF 28
- H.264 for compatibility
- Mono audio at 64kbps
Step 3: Test and Compare
Always compare compressed output against original:
- Check for artifacts (blocking, banding)
- Verify audio sync
- Confirm colors look correct
- Test on target device/platform
Common Mistakes to Avoid
Re-compressing Already Compressed Video
Each compression cycle degrades quality. Always work from original sources when possible.
Using Wrong Preset
Slower presets produce better quality at the same file size:
ultrafast < superfast < veryfast < faster < fast < medium < slow < slower < veryslow
Use slow or slower when time permits.
Ignoring Audio
Over-compressed audio is noticeable. Keep audio at 128kbps minimum for music.
Advanced Techniques
Two-Pass Encoding
For precise file size targeting:
# Pass 1 - Analyze
ffmpeg -i input.mp4 -c:v libx264 -b:v 2M -pass 1 -f null /dev/null
# Pass 2 - Encode
ffmpeg -i input.mp4 -c:v libx264 -b:v 2M -pass 2 output.mp4
Hardware Acceleration
Modern GPUs can encode much faster:
- NVIDIA:
-c:v h264_nvenc - AMD:
-c:v h264_amf - Intel:
-c:v h264_qsv
Conclusion
Effective video compression is about understanding your content and delivery requirements. Start conservative with CRF 23, test your results, and adjust as needed. Use our converter's Advanced Options to fine-tune these settings without any command-line knowledge.
