Variable bit rate

Variable bit rate (VBR) is a type of encoding often used in encoding to lossy formats like MP3, OGG, WMA and MP4 which allows more bits to be used for hard-to-encode passages and less for simpler passages and silences. The quality to be achieved is set as a target bitrate range or a quality level. Variable bit rate encoding avoids a common problem with constant bit rate (CBR) encoding, where quality is perceived to decline in loud and complex passages. As a result, variable bit rate encoding tends to increase perceived overall quality somewhat for the same or slightly less filesize.