Bitrate is the number of bits processed per second in a media stream. It is expressed in kilobits per second (kbps) or megabits per second (Mbps), and higher values generally allow better quality at larger file sizes.
Why it matters
Bitrate sets both quality and cost: file size and streaming bandwidth scale directly with it. A viewer's connection must be faster than the stream bitrate or the video buffers. Constant bitrate keeps the data rate fixed, while variable bitrate gives more bits to complex scenes.
Quality also depends on the codec, so the same bitrate looks better with a newer one.
Example
File size = bitrate x duration / 8
5 Mbps x 600 s / 8 = 375 MB (a ten-minute video)
128 kbps x 3600 s / 8 = 57.6 MB (one hour of audio)Common mistakes
- Mixing bits and bytes: 8 megabits equal 1 megabyte.
- Raising bitrate on a poor source and expecting better quality.
- Offering only one high bitrate to visitors on slow mobile connections.
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