Bitrate refers to the size, over time, of a video or audio stream. Although most computer oriented applications measure bitrate in terms of binary kilobits and Megabits where 1kb (1 kilobit) = 1024 bits and 1Mb (1 Megabit) = 1024 kilobits, bitrate calculations use standard metric values for these prefixes, meaning 1kb = 1000b and 1Mb = 1000kb. Bitrate calculations are typically made in kilobits per second (kbps) or Megabits per second (Mbps). They can also be expressed in other units, including bits per second (bps) or even Megabytes per second (MBps). Notice the capital B denoting Bytes. You should always use a lower case b to denote bits and upper case for Bytes.
In digital multimedia, bitrate represents the amount of information, or detail that is stored per unit of time of a recording. The bitrate depends on several factors:
Generally, choices are made about the above factors in order to achieve the desired trade-off between minimizing the bitrate and maximizing the quality of the material when it is played.
If lossy data compression is used on audio or visual data, differences from the original signal will be introduced; if the compression is substantial, or lossy data is decompressed and recompressed, this may become noticeable in the form of compression artifacts. Whether these affect the perceived quality, and if so how much, depends on the compression scheme, encoder power, the characteristics of the input data, the listener’s perceptions, the listener's familiarity with artifacts, and the listening or viewing environment.
The bitrates in this section are approximately the minimum that the average listener in a typical listening or viewing environment, when using the best available compression, would perceive as not significantly worse than the reference standard:
Audio (MP3)
Other audio
Video
Notes
For technical reasons (hardware/software protocols, overheads, encoding schemes, etc.) the actual bitrates used by some of the compared-to devices may be significantly higher than what is listed above. For example: