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Constant bitrate (CBR) is a term used in telecommunications, relating to the quality of service
Quality of service

In the field of computer networking and other packet-switched telecommunication networks, the Traffic engineering term quality of service refers to resource reservation control mechanisms rather than the achieved service quality....
. Compare with variable bitrate
Variable bitrate

Variable bitrate is a term used in telecommunications and computing that relates to the bitrate used in sound or video encoding. As opposed to constant bitrate , VBR files vary the amount of output data per time segment....
.

When referring to codec
Codec

A codec is a device or computer program capable of encoder and/or Decoding methods a digital data stream or signal . The word codec is a portmanteau of 'compressor-decompressor' or, most commonly, 'coder-decoder'....
s, constant bit rate encoding
Encoding

Encoding is the process of transforming information from one format into another. The opposite operation is called decoding.There are a number of more specific meanings that apply in certain contexts:...
 means that the rate at which a codec's output data should be consumed is constant. CBR is useful for streaming multimedia content on limited capacity channels since it is the maximum bit rate that matters, not the average, so CBR would be used to take advantage of all of the capacity.






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Constant bitrate (CBR) is a term used in telecommunications, relating to the quality of service
Quality of service

In the field of computer networking and other packet-switched telecommunication networks, the Traffic engineering term quality of service refers to resource reservation control mechanisms rather than the achieved service quality....
. Compare with variable bitrate
Variable bitrate

Variable bitrate is a term used in telecommunications and computing that relates to the bitrate used in sound or video encoding. As opposed to constant bitrate , VBR files vary the amount of output data per time segment....
.

When referring to codec
Codec

A codec is a device or computer program capable of encoder and/or Decoding methods a digital data stream or signal . The word codec is a portmanteau of 'compressor-decompressor' or, most commonly, 'coder-decoder'....
s, constant bit rate encoding
Encoding

Encoding is the process of transforming information from one format into another. The opposite operation is called decoding.There are a number of more specific meanings that apply in certain contexts:...
 means that the rate at which a codec's output data should be consumed is constant. CBR is useful for streaming multimedia content on limited capacity channels since it is the maximum bit rate that matters, not the average, so CBR would be used to take advantage of all of the capacity. CBR would not be the optimal choice for storage as it would not allocate enough data for complex sections (resulting in degraded quality) while wasting data on simple sections.

The problem of not allocating enough data for complex sections could be solved by choosing a high bitrate (eg, 256 kbit/s or 320 kbit/s) to ensure that there will be enough bits for the entire encoding process, though the size of the file at the end would be proportionally larger.

Most coding schemes such as Huffman coding
Huffman coding

In computer science and information theory, Huffman coding is an entropy encoding algorithm used for lossless data compression. The term refers to the use of a variable-length code table for encoding a source symbol where the variable-length code table has been derived in a particular way based on the estimated probability of occurrence for...
 or run-length encoding
Run-length encoding

Run-length encoding is a very simple form of data compression in which runs of data are stored as a single data value and count, rather than as the original run....
 produce variable-length codes, making perfect CBR difficult to achieve. This is partly solved by varying the quantization (quality), and fully solved by the use of padding. (However, CBR is implied in a simple scheme like reducing all 16-bit audio samples to 8-bits.)

See also

  • Bitrate
    Bitrate

    In telecommunications and computing, bitrate is the number of bits that are conveyed or processed per unit of time.The bit rate is quantified using the Data rate units unit, often in conjunction with an SI prefix such as kilo- , mega- , giga- or tera- ....
  • Average bitrate
    Average bitrate

    Average bitrate refers to the average amount of data transferredper unit of time, usually measured per second. This is commonly referred to for digital music or video....
  • Variable bitrate
    Variable bitrate

    Variable bitrate is a term used in telecommunications and computing that relates to the bitrate used in sound or video encoding. As opposed to constant bitrate , VBR files vary the amount of output data per time segment....