Variable Bitrate (VBR) is a term used in digital audio and video compression. In a VBR encoding, the bitrate (i.e. the number of bits used to represent a unit of time of the audio or video content) is allowed to vary throughout the stream. In contrast, with a Constant Bitrate (CBR) encoding, the bitrate remains constant throughout the entire stream.
The main advantage of using VBR encoding is that it can provide better audio and video quality for a given file size compared to CBR encoding. This is because the bitrate can be increased in areas of the stream that require more bits to maintain the desired quality, and decreased in areas where fewer bits are needed. This allows for a more efficient use of bits, resulting in a smaller file size while still maintaining a high level of quality.
However, VBR encoding can also lead to a more complex encoding process and may not be compatible with all playback devices or streaming systems. Additionally, VBR encoding may not be suitable for applications where a constant bitrate is required, such as in live broadcasting or streaming.