Video Bitrate Optimization for Streaming Delivery
Choosing the right bitrate balances video quality with buffering risk. Adaptive bitrate streaming solves this by serving multiple quality levels based on viewer bandwidth.
Key Takeaways
- Bitrate is the number of bits processed per second of video.
- Constant Bitrate (CBR): Same bitrate throughout.
- Streaming services encode each video at multiple quality levels.
- Netflix pioneered per-title encoding β analyzing each video's complexity to create a custom bitrate ladder.
- Start with recommended bitrates and adjust based on content type
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What Bitrate Controls
Bitrate is the number of bits processed per second of video. Higher bitrate means more data per frame, which generally means better quality β but also larger files and higher bandwidth requirements.
Fixed vs Variable Bitrate
Constant Bitrate (CBR): Same bitrate throughout. Predictable file size but wastes bits on simple scenes and starves complex ones.
Variable Bitrate (VBR): Allocates bits based on scene complexity. Better quality-per-byte but unpredictable file sizes.
Constrained VBR: VBR with a maximum bitrate cap. Best of both worlds for streaming β adapts to content while preventing bandwidth spikes.
Bitrate Ladder
Streaming services encode each video at multiple quality levels. A typical ladder:
| Resolution | Bitrate | Target |
|---|---|---|
| 360p | 600 kbps | 2G/slow mobile |
| 480p | 1.5 Mbps | 3G/mobile |
| 720p | 3 Mbps | WiFi/4G |
| 1080p | 6 Mbps | Broadband |
| 4K | 15 Mbps | Fast broadband |
Per-Title Encoding
Netflix pioneered per-title encoding β analyzing each video's complexity to create a custom bitrate ladder. An animated cartoon needs far fewer bits than a live-action scene with rain and confetti.
Practical Tips
- Start with recommended bitrates and adjust based on content type
- Animated content can use 30-50% lower bitrates
- Fast-motion sports need 20-30% higher bitrates
- Always cap maximum bitrate for streaming delivery