variable bit rate (ATM) (VBR)

Variable bit rates (VBR) are used for quantization in codecs, but also in data transmission.

1. Various audio codecs such as Ogg Vorbis or the MPC format are designed for variable bit rate (VBR) quantization, which allows lower frequencies to be digitized at a lower sampling rate, while higher frequencies can be digitized at a higher sampling rate. The advantage of this technique is optimized sampling and a smaller file size.
2. The ATM Forum has defined two classes of service for variable bit rate data transmission: real-time transmission (VBR/rt) and non-real-time transmission (VBR/nrt). Both classes of service support variable bit rate traffic. However, real-time transmission requires strict adherence to time synchronization for medium traffic flows and peak loads, as it is used for voice and video transmission. In non-real-time transmission, a variable but predictable delay is tolerated. Variable Bit Rates (VBR) in real-time is ideal for transmission of compressed voice and interactive multimedia applications. The non-real-time version of VBR is optimal for critical data transmission.