Constant bit rate (CBR) is a data compression scheme where the rate of the audio or video data stream is fixed. Since the amount of compression varies to match the fixed data rate, audio or video quality may suffer, particularly during the output of complex segments of data. CBR is useful for streaming multimedia content on channels with limited capacity. Since only the maximum data rate is taken into account in such a stream, all of the capacity of the channel can be used to full advantage. However, for data storage, CBR is not the optimal choice, as it may not allocate enough storage space for complex regions of data, and may allow too much space for less complex data.