Glossary
Bitrate
Bitrate is the number of bits transmitted per second in an audio or video stream. It is the primary control that balances stream quality against bandwidth consumption in real-time calling and recorded media.
General definition
Bitrate is expressed in kilobits per second (kbps) or megabits per second (Mbps). For a given video codec, a higher bitrate allows more detail per frame, finer colour gradation, and smoother motion, while a lower bitrate compresses more aggressively, introducing artefacts and blur. The codec and the encoder settings determine how efficiently a given bitrate is used.
- Audio: typical voice calls use 8-64 kbps; high-quality music-grade audio uses up to 320 kbps
- Video: typical SD calls use 500-1,000 kbps; HD calls use 1.5-4 Mbps; 4K can require 15 Mbps or more
- Adaptive bitrate (ABR) systems vary the rate dynamically to match available bandwidth
- Constant bitrate (CBR) uses a fixed rate regardless of content complexity
In WebRTC, bitrate is negotiated during session setup via SDP and can be adjusted dynamically using bandwidth estimation (REMB or TWCC). Simulcast allows a single publisher to send streams at multiple bitrates so the SFU can select the right layer per subscriber.
In the Ethora ecosystem
Ethora’s voice and video calling layer, built on WebRTC, adapts bitrate continuously to each participant’s network conditions. This keeps calls clear and connected for users on variable connections without requiring manual configuration by the end user.
In a self-hosted Ethora deployment, engineering teams can set bitrate caps and floor values in the media server configuration to match their available uplink bandwidth and storage cost targets, which is particularly relevant for organisations with bandwidth-constrained clinic or branch-office networks.
