Turns on encoding with a targeted average bitrate of n kbits, allowing to
use frames of different sizes. The allowed range of n is 4-310, you can use
any integer value within that range.
Joint-stereo is the default mode for stereo files with VBR when -v is more
than 4 or fixed bitrates of 160kbs or less. At higher fixed bitrates or higher
VBR settings, the default is stereo.
stereo
Normal stereo mode.
joint stereo
In this mode, the encoder will make use of a correlation between both channels
in order to achieve higher compression. This will enhance the quality of constant
bitrate recordings, and reduce the size of variable bitrate recordings.