What is the VBR (Variable Bit Rate) encording in MP3?
Some audio passages are more difficult to encode than others. In order to maintain constant bitrate (CBR) during CBR encoding, difficult passages may be encoded with fewer than the desired number of bits with a consequent decrease in quality level relative to the average bitrate. During easy passages the encoder uses more than the necessary number of bits in order to maintain constant bitrate. In essence, fixed bitrate operation varies the quality level in order to maintain constant bitrate. Conversely, variable bitrate (VBR) operation fixes the quality level and allows bitrate to vary. During difficult passages VBR uses a higher than average bitrate and during easy passages uses a lower than average bitrate. The net result is that VBR produces an overall higher, more consistent quality level compared to CBR at similar bitrates. With CBR, you can compress the sound with fixed size no matter how it may be complicated or not. On the contrary, with VBR, you have to make the size of sound
