Selecting Encoding Mode

There are two encoding modes you can use: Variable Bitrate (VBR) encoding and Constant Bitrate (CBR) encoding. Since the VBR approach is more flexible and yields better results than the CBR approach at similar bitrates, we recommend you use VBR. Be warned, however, that some of the existing MPEG decoders do not read the VBR-encoded audio files.

Why VBR is better than CBR ?

Some audio passages are more difficult to encode than others. In order to maintain Constant Bitrate during CBR encoding, difficult passages may be encoded with less 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 operation fixes the quality level and allows bitrate to vary. During difficult passages, VBR uses a higher than average bitrate. During easy passages, VBR 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.