Bitrate

Bitrate is the rate at which encoded data is transmitted or stored per unit of time, expressed in bits per second (bps), kilobits per second (kbps) or megabits per second (Mbps). In post-production, bitrate decisions determine file size, image quality, and pipeline performance at every stage. Two encoding strategies coexist: constant bitrate (CBR) maintains a fixed data rate throughout the file, predictable for streaming and live broadcast but inefficient on static or low-detail scenes; and variable bitrate (VBR) allocates more bits to complex frames and fewer to simple ones, producing better quality at the same average rate but unpredictable peak loads. Modern codecs add constrained-VBR and capped-VBR variants that combine the benefits. Typical bitrates for reference: 4K UHD Netflix delivery 15–25 Mbps (H.265 main10), 4K UHD ProRes 422 HQ around 884 Mbps (intra-frame mastering), 4K UHD ProRes 4444 XQ around 1.9 Gbps (finishing), 4K UHD Blu-ray HEVC 50–100 Mbps. Camera RAW bitrates are vastly higher — ARRI ALEXA 35 in ARRIRAW can exceed 4 Gbps. The choice of bitrate must match purpose: mezzanine codecs (mastering and grading) prioritize quality with high bitrates and intra-frame compression; distribution codecs (streaming, broadcast) prioritize bandwidth efficiency with lower bitrates and inter-frame prediction. Reference: ISO/IEC 14496-10 (H.264), ITU-T H.265 (HEVC), and SMPTE ST 2067 for IMF bitrate constraints.