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>

Update FATE references accordingly.

Use 'auto' as the default value.

Function pointers are used for templated functions instead of needlessly
duplicating many functions.

This reverts commit 7b8ec38d.

The copyright date was wrong.

The code was originally committed to Libav on March 25, 2011.

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

This adds basic stream format support and allows for arbitrary bit rates
rather than just those supported in AC-3.

use only selected options for the different AC-3 encoder types.