for example:
Attempting to set ac3 dsur_mode to "on" results in:
[AC-3 Encoder @ 0x7f508f0a3280] Value 2.000000 for parameter 'dsur_mode' out of range
[AC-3 Encoder @ 0x7f508f0a3280] Error setting option dsur_mode to value on.
Signed-off-by: Justin Ruggles <justin.ruggles@gmail.com>