Bitrate is the amount of data used per second of video, measured in kbps or Mbps. It is the main lever on the quality–cost trade-off: a higher bitrate carries more detail and looks better, but every extra bit is bytes that must be stored and, far more expensively, delivered to every viewer. Because delivery (egress) is usually the largest recurring cost in OTT, bitrate is effectively a cost dial.
Encoding can use constant bitrate (CBR), which holds a steady rate regardless of scene complexity, or variable bitrate (VBR), which spends bits where the picture needs them and saves them on simple scenes. Constrained VBR is the common compromise. Crucially, bitrate is not the same as quality: a newer codec (HEVC, AV1) or a better encoder can reach the same perceived quality at a lower bitrate.
Each rung of the encoding ladder is defined largely by its bitrate, and the player's ABR logic selects rungs by comparing their bitrates against measured throughput.
