Normalize AC3 sound

[pekseg]

consider to use the -dnorm switch for aften. Sometimes the output ac3 sound is too quiet/low.
(possible value is 27, so : "-dnorm 27" should be set as a parameter for aften.)

[JakeWharton]

I'm thinking of adding passthrough arguments for all subprograms. So in your case you'd do mkvdts2ac3.sh --aften-dnorm 27 .... This way I don't have to individually support features that some people need on occasion (like the -o argument).