CBR (constant bitrate) encoding holds a fixed number of bits per second regardless of how simple or complex the audio is at any moment. Its virtue is predictability: stream planners know the exact bandwidth, packets are uniform, and it is easy to fit into a fixed-rate channel or a streaming ladder rung. The cost is efficiency — quiet or simple passages waste bits they don't need while complex passages may get fewer than they'd like — so at a given average rate CBR is usually slightly worse quality than VBR. It remains common where the transport demands a steady rate, such as broadcast multiplexes and some real-time links.
