[mythtv-users] HDPVR audio out of sync in 5.1 AC-3 mode

[Oz]

When I change my Sat Box from PCM to Dolby digital and the

HDPVR Audio encoding to 4 (AC-3). The audio is significantly lagging 
behind the video (possibly 2 seconds)

If I will not do the changes above (i.e Keep the cable box at PCM, and 
HDPVR at AAC)

I will get digital sound but only 2 speakers not 5.1 The source is 5.1

Is there a way to get 5.1 sound synced

My setup is (ubuntu 9.04, mythtv 0.22 nvidia 8600gts and 4gb ram intel 
quad 2.4gz, vpdau)

-Thanks