CBR (constant bitrate)
CBR (constant bitrate) is a video encoding mode that keeps the data rate roughly the same throughout a stream, whatever the scene complexity. CBR makes bandwidth use predictable. Simple scenes may waste bits, while complex scenes such as fast sports action may look worse. CBR is widely used for live streaming ingest.
Why it matters
CBR gives predictable bandwidth, which keeps live ingest stable and makes delivery costs easy to forecast. The price is wasted bits on simple scenes and weaker quality on complex ones. For on-demand video, that usually means paying for more data than needed. For a live event business, the FastPix bill does not depend on encoder settings either: live encoding is a flat rate per minute ingested up to 1080p, so cost follows hours streamed and viewers.
How it works
- You set a target bitrate, such as 6 Mbps, in the encoder.
- The encoder adjusts compression frame by frame to hold close to that rate.
- Complex scenes are compressed harder, and simple scenes may be padded to keep the rate steady.
- A buffer setting controls how far the rate may drift over short periods.
CBR vs VBR: which is better for streaming?
Use CBR for live streaming ingest and VBR for on-demand video. CBR's steady rate suits live connections and ingest servers, and YouTube Live recommends it. VBR gives better quality at the same average size, so on-demand services prefer it, usually with a maximum bitrate cap.
What bitrate should I use for CBR live streaming?
Pick a CBR bitrate below what your upload connection can reliably sustain, then match it to resolution. As a rough guide, many platforms suggest a few Mbps for 720p and more for 1080p at 60 fps. Leave headroom, since an upload that cannot keep up causes dropped frames and buffering for viewers.
Where it's used
Live sports and live event streamers send a constant bitrate from their encoders, because ingest servers and networks handle a steady data rate more reliably. On-demand services usually prefer variable bitrate.
Where it usually goes wrong, and how FastPix handles it
Teams often set a CBR rate higher than their venue upload can hold, so the encoder drops frames and viewers buffer, and the cause is hard to spot from the viewer side.
During the event, FastPix shows stream health stats for each incoming RTMPS or SRT feed. Video Data records buffer count, buffer ratio and dropped frames per view, so a live team can tell an ingest problem from a viewer network problem and fix the right one during the event.
By the numbers
- YouTube Live's recommended encoder settings specify CBR bitrate encoding. (YouTube Help: Choose live encoder settings, bitrates, and resolutions)
