In
telecommunications, average bitrate (ABR) refers to the average amount of data transferred per unit of time, usually measured per second, commonly for
digital music or
video. An
MP3 file, for example, that has an average
bit rate of 128
kbit/s transfers, on average, 128,000
bits every second. It can have higher bitrate and lower bitrate parts, and the average bitrate for a certain timeframe is obtained by dividing the number of bits used during the timeframe by the number of seconds in the timeframe. Bitrate is not reliable as a standalone measure of
audio
Audio most commonly refers to sound, as it is transmitted in signal form. It may also refer to:
Sound
*Audio signal, an electrical representation of sound
*Audio frequency, a frequency in the audio spectrum
* Digital audio, representation of sou ...
or
video quality, since more efficient compression methods use lower bitrates to encode material at a similar quality.
Average bitrate can also refer to a form of
variable bitrate (VBR) encoding in which the
encoder will try to reach a target average bitrate or
file size while allowing the bitrate to vary between different parts of the audio or video. As it is a form of variable bitrate, this allows more complex portions of the material to use more bits and less complex areas to use fewer bits. However, bitrate will not vary as much as in variable bitrate encoding.
[.] At a given bitrate, VBR is usually higher quality than ABR, which is higher quality than CBR (
constant bitrate).
[.] ABR encoding is desirable for users who want the general benefits of VBR encoding (an optimum bitrate from frame to frame) but with a relatively predictable file size.
Two-pass encoding is usually needed for accurate ABR encoding, as on the first pass the encoder has no way of knowing what parts of the audio or video need the highest bitrates to be encoded.
See also
*
Variable bitrate
*
Constant bitrate
References
External links
* .
* .
Codecs
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