Bitrate mode (CBR vs VBR)
Also known as: CBR vs VBR, constant bitrate, variable bitrate, bitrate control
Bitrate mode controls how an encoder spends data over time. Constant bitrate (CBR) holds a steady data rate throughout, while variable bitrate (VBR) spends more on complex scenes and less on simple ones — usually giving better quality per megabyte for a similar file size.
- CBR holds a steady data rate; VBR varies it
- VBR usually gives more quality per megabyte
- CBR suits live streaming and fixed bandwidth
CBR vs VBR
CBR keeps the data rate fixed for the whole clip. It is predictable and well suited to live streaming, where a steady rate keeps playback stable, but it can waste data on simple scenes and starve complex ones.
VBR lets the bitrate rise and fall with scene difficulty, giving busy, high-motion sections more bits and quiet, static sections fewer. For the same target size, VBR generally looks better; for the same quality, it can be smaller.
Choosing a mode for size and quality
For downloads, archives, and most compression jobs, VBR is the usual choice because it spends data where the eye notices it. Two-pass VBR analyzes the video first, then allocates bits even more efficiently for a tighter, better-looking file.
CBR makes sense when a constant rate is required — fixed-bandwidth streaming or strict size budgets per second — accepting that simple scenes may carry more data than they need.