[mythtv] ffmpeg sync

[Mark Spieth]

janne

Ive been running your ffmpeg sync for a while now and I think there is a 
problem with ac3dec
it seems to sound "furry". audio quality is definitely reduced.
Im rebuilding without ac3_decoder and with liba52bin to double check things. 
but not tonight.
this is a change from the previous ffmpeg which disabled ac3dec and used 
liba52 only.
no other problems noticed so far but then again I only excercise mpeg2,. 
xvid/mpeg4, mp3, mp2 and ac3.
Im also noticing some FE crashes too but not sure if they are related and 
havent had time to chase them yet.

cheers
mark