TL;DR
- Video bitrate directly impacts streaming quality and bandwidth consumption. Higher bitrates improve visual quality but increase data usage and delivery costs; lower bitrates reduce bandwidth requirements but may degrade quality
- Adaptive bitrate (ABR) streaming relies on multiple bitrate renditions
- HLS and MPEG-DASH require encoding video into several bitrate/resolution variants so players can dynamically switch based on available network conditions
- An optimized bitrate ladder balances resolution, compression efficiency, and network variability to ensure smooth playback across device types and connection speeds
- High-motion or visually complex content requires higher bitrates to maintain quality compared to static or low-motion video
- Advanced codecs (e.g., HEVC, AV1) can deliver comparable quality at lower bitrates compared to older codecs, improving streaming efficiency and cost-effectiveness
Video Bitrates for Streaming
Choosing an appropriate streaming bitrate for a specific resolution, while maintaining an acceptable visual quality is not always that easy. The decision depends heavily on the content, e.g., motion, resolution, video bitrate, frame-rate etc. In adaptive streaming systems like MPEG Dynamic Adaptive Streaming over HTTP (DASH) and Apple HTTP Live Streaming (HLS) the first decision that needs to made is: What is the minimum and maximum bitrate/resolution that the system should serve to the users? This depends of course on the resolution and bitrate of the input content and on the network conditions that most of your users are facing, e.g., mobile networks (3G, 4G) with bandwidth fluctuations from x to y and fixed networks with the same variances but in another range.
As a rule of thumb, the Bitmovin team recommends minimum, average and maximum bitrates for common resolutions visualized through the following graph. The horizontal axis of the graph shows the pixels per second, on a logarithmic scale, that are needed for the resolutions with 24 frames per second and the vertical axis shows the encoding bitrate in Kbps.
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Resolution and Bitrate Recommendation
The minimum, average and maximum functions of the previous graph are also visualized in the following table view. This view also contains the bits spend per pixel when encoded with the recommended bitrate. It can be seen that the bits per pixel are decreasing with increasing resolutions due to the fact that H.264/AVC is more efficient for higher resolutions.
Minimum Video Bitrate
| Resolution | FPS | Bitrate (Kbps) | Bits per Pixel |
|---|---|---|---|
| 426×240 | 24 | 250 | 0.10 |
| 640×360 | 24 | 500 | 0.09 |
| 854×480 | 24 | 750 | 0.08 |
| 1280×720 | 24 | 1500 | 0.07 |
| 1920×1080 | 24 | 3000 | 0.06 |
| 4096×2160 | 24 | 10000 | 0.05 |
Average Video Bitrate
| Resolution | FPS | Bitrate (Kbps) | Bits per Pixel |
|---|---|---|---|
| 426×240 | 24 | 400 | 0.17 |
| 640×360 | 24 | 800 | 0.15 |
| 854×480 | 24 | 1200 | 0.12 |
| 1280×720 | 24 | 2400 | 0.11 |
| 1920×1080 | 24 | 4800 | 0.10 |
| 4096×2160 | 24 | 16000 | 0.08 |
Maximum Video Bitrate
| Resolution | FPS | Bitrate (Kbps) | Bits per Pixel |
|---|---|---|---|
| 426×240 | 24 | 700 | 0.29 |
| 640×360 | 24 | 1400 | 0.26 |
| 854×480 | 24 | 2100 | 0.22 |
| 1280×720 | 24 | 4200 | 0.19 |
| 1920×1080 | 24 | 8400 | 0.17 |
| 4096×2160 | 24 | 28000 | 0.14 |
- Did you hear of Per-Scene Adaptation? It helps reducing the bandwidth consumption by adjusting the bitrate stream to the minimum bitrate required to maintain perfect visual quality for every segment within your video. Read more about it here.
- Per-Title Ladder Benchmarking Tool: Test your Content and see a comparison of your existing bitrate ladder (or a standard default ladder) against the optimized Per-Title ladder.
- Video Developer Report 2019: Key insights into the evolving technology trends of the digital video industry
FAQs
1. What is video bitrate in streaming?
Video bitrate refers to the amount of data processed per second in a video stream, typically measured in kbps or Mbps. It determines visual quality, file size, and bandwidth requirements.
2. Why is bitrate important for HLS and DASH streaming?
Both HLS and MPEG-DASH use adaptive bitrate streaming. The player switches between bitrate renditions in real time depending on network conditions. Poor bitrate selection can cause buffering, low quality, or excessive delivery costs.
3. What is a bitrate ladder?
A bitrate ladder is a set of encoded video renditions at different resolutions and bitrates. It enables adaptive streaming systems to dynamically select the most appropriate quality level for each viewer.
4. How does content type affect bitrate selection?
High-motion content such as sports or action scenes requires higher bitrates to maintain visual fidelity. Low-motion content such as interviews or presentations can achieve comparable quality at lower bitrates.
5. How does adaptive bitrate switching work in practice?
The video is segmented into small chunks at multiple quality levels. The player measures available throughput and switches between bitrate variants on a per-segment basis to avoid buffering while maximizing quality.
