benchmark (on intel core2 duo, gcc 4.9.1)
input samples duration 00:03:39.59
command: time -p ffmpeg -f f32le -ac 2 -ar 44100 -i input.pcm \
         -filter_complex showcqt=fullhd=0:gamma=$gamma \
         -f rawvideo -y /dev/null
gamma  previous  modified
  1    48.49 s   45.38 s
  2    49.33 s   48.11 s
  3    80.86 s   59.80 s
  4    80.84 s   51.25 s
  5    80.75 s   61.06 s
  6    80.93 s   61.80 s
  7    80.03 s   61.56 s
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>