    ----------------------------------------------------
    RT_PVC
    Ge Wang, Ahmed Abdallah, Paul Botelho
    http://soundlab.cs.princeton.edu/
    ----------------------------------------------------
    's' - toggle fullscreen
    '-' - decrease frequency factor
    '=' - increase frequency factor
    SHIFT('-') - decrease time factor
    SHIFT('=') - increase time factor
    '(' - decrease hop size
    ')' - increase hop size
    'p' - toggle phase adjustment
    'd' - toggle dB plot for spectrum
    'w' - toggle wuterfall plot
    'f' - move spectrum - z
    'j' - move spectrum - z
    'e' - spacing more!
    'i' - spacing less!
    L, R mouse button - rotate left or right
    'h' - print this help message
    'g' - freeze
    'q' - quit
    ----------------------------------------------------
