Number of sampling per second
the number of bits of information recorded for each sample
Mono: Mono data uses one channel.
Stereo: Stereo data uses two channels
In this mode, the bitrate will be the same for the whole file. It means that each part of your wma file will be using the same number of bits
With variable bit rate WMAs, the encoder automatically detects which bit rate is most appropriate for the sound being encoded.