[mythtv-users] AC3 frame sync errors

[paul10 at planar.id.au]

I'm having problems playing back iso / DVD files in mythvideo (yes, I
know, again).  I'm running trunk, and will log a defect if someone here
doesn't tell me the obvious error that I've made :-)

In general the videos are playing well through the usual warnings etc,
until I get past the main menu and to the title (OK, sample size of 2
here, I can try more, but there are at least 2 that don't work).

When I start the main feature, it is hanging, and giving a huge stream of
"AC3 frame sync error" messages.  I've googled, there are a couple of
references to similar problems, none with a resolution.  This defect:
http://www.gossamer-threads.com/lists/mythtv/commits/341449 and
http://svn.mythtv.org/trac/ticket/5536
is similar, but implies there is a work around.  Mine is doing it when set
to stereo, so I seem to have nowhere to go.

I've run mythfrontend -v audio, and get the following relevant looking
messages:
2009-03-07 12:04:30.384 AFD: Audio is disabled - trying to restart it
2009-03-07 12:04:30.384 AFD: Selected track 1: English AC3 7ch (A/V Stream
#8)
2009-03-07 12:04:30.384 AFD: Initializing audio parms from audio track #1
2009-03-07 12:04:30.384 AFD: Audio format changed
                        from id(NONE)    -1Hz -1ch   0bps    ; id( AC3)
48000Hz  2ch  16bps
                        to   id( AC3) 48000Hz  6ch  16bps    ; id( AC3)
48000Hz  2ch  16bps
2009-03-07 12:04:30.385 AO: Killing AudioOutputDSP
2009-03-07 12:04:30.385 Opening audio device 'default'. ch 2(2) sr 48000
2009-03-07 12:04:30.385 Opening ALSA audio device 'default'.
2009-03-07 12:04:30.416 in SetParameters(format=2, channels=2, rate=48000,
buffer_time=400000, period_time=25000)
2009-03-07 12:04:30.417 get_buffer_size returned 8192
2009-03-07 12:04:30.417 set_period_time_near returned 21333
2009-03-07 12:04:30.417 get_period_size returned 1024
2009-03-07 12:04:30.417 Opening mixer default
2009-03-07 12:04:30.417 Setting Master volume to 70
2009-03-07 12:04:30.417 Volume range is 0 to 31, mult=3.22581
2009-03-07 12:04:30.417 channel 0 vol set to 22
2009-03-07 12:04:30.417 Volume range is 0 to 255, mult=0.392157
2009-03-07 12:04:30.417 Volume range is 0 to 255, mult=0.392157
2009-03-07 12:04:30.417 ALSA: channel 0 playback switch set to 1
2009-03-07 12:04:30.417 Setting Master volume to 70
2009-03-07 12:04:30.417 mixer unable to find control Master 1
2009-03-07 12:04:30.417 Setting PCM volume to 100
2009-03-07 12:04:30.417 Volume range is 0 to 255, mult=0.392157
2009-03-07 12:04:30.418 channel 0 vol set to 255
2009-03-07 12:04:30.418 Setting PCM volume to 100
2009-03-07 12:04:30.418 Volume range is 0 to 255, mult=0.392157
2009-03-07 12:04:30.418 channel 1 vol set to 255
2009-03-07 12:04:30.418 Volume range is 0 to 255, mult=0.392157
2009-03-07 12:04:30.418 AO: Audio fragment size: 6144
2009-03-07 12:04:30.418 AO: Audio Stretch Factor: 1
2009-03-07 12:04:30.418 Audio Codec Used: not set
2009-03-07 12:04:30.418 AO: Ending reconfigure
2009-03-07 12:04:30.418 AO: kickoffOutputAudioLoop: pid = 10431
2009-03-07 12:04:30.418 NVP(0): Enabling Audio
2009-03-07 12:04:30.418 AO: OutputAudioLoop: Play Event
2009-03-07 12:04:30.418 AO: no change exiting
2009-03-07 12:04:30.418 [ac3 @ 0xb71a0190]frame sync error
2009-03-07 12:04:30.418 [ac3 @ 0xb71a0190]frame sync error
2009-03-07 12:04:30.418 [ac3 @ 0xb71a0190]frame sync error
2009-03-07 12:04:30.418 [ac3 @ 0xb71a0190]frame sync error
2009-03-07 12:04:30.418 [ac3 @ 0xb71a0190]frame sync error
2009-03-07 12:04:30.418 [ac3 @ 0xb71a0190]frame sync error

which then continues ad infinitum so far as I can tell.

Is there some obvious mistake I'm making?  I'm getting the same behaviour
on two different machines - different motherboards, audio chips, only one
is VDPAU enabled, both are running trunk version 20114.