[mythtv-users] Intermittent audio issues - snd-via82xx

[Ben Lancaster]

Hey,

OK, really odd stuff happening here. I have an onboard VIA 82xx AC'97  
soundcard, with the following in my modprobe.conf:

alias snd-card-0 snd-via82xx
options snd-via82xx index=0
options snd-via82xx dxs_support=5

The dxs_support line came from a flag in my dmesg:

via82xx: Assuming DXS channels with 48k fixed sample rate.
          Please try dxs_support=5 option
          and report if it works on your machine.
          For more details, read ALSA-Configuration.txt.

According to ALSA-Configuration.txt:

dxs_support - support DXS channels,
                   0 = auto (default), 1 = enable, 2 = disable,
                   3 = 48k only, 4 = no VRA, 5 = enable any sample
                   rate and different sample rates on different
                   channels
                   [VIA8233/C, 8235, 8237 only]

Changing its value didn't seem to make the slightest bit of difference.

I have two devices: /dev/dsp and /dev/adsp

First question (probably a stupid one): what's the difference between  
the two?

Now down to the problems:

/dev/dsp
this makes myth sound like its in the bath: two simultaneous copies  
of the same audio stream, but one slightly delayed (can't be more  
than 1/10th of a second), with varying delays accross channels

/dev/adsp
Audio is (intermittently, usually after a reboot) anywhere between  
200ms-1000ms out of sync

/dev/adsp seems to be the most reliable. I've tried tinkering with  
the mythtv settings relating to audio, but none has made a difference

The next problem, which I'm guessing is all part of the same problem  
is frame skipping (not dropping). Once audio/video has been fine for  
a while (could be anywhere from 1-24 hours), something suddenly makes  
the audio/video start skipping a couple of frames every 10-15  
seconds. The interval between skips is totally unpredictable, as is  
the trigger. Absolutely nothing abnormal shows up in the logs when it  
starts to skip either. This doesn't just apply to MythTV, but any AV  
playback app. Once the problem's started and you exit live tv/playing  
a recording, the screen goes black and loops the last ~200ms of audio  
seamlessly for around 5-10s before returning back to the menu.

The only thing that seems to fix the problem (albeit temporarily) is  
a reboot.

No combination of MythTV's settings seem to improve/degrade things  
either,

Here's my vitals:

Kernel 2.6.16-1.2133_FC5 (x86_64) on Fedora Core 5
MythTV 0.19 x86_64 (latest ATRPMS)
NVidia GF-FX5200
VIA Technologies, Inc. VT8233/A/8235/8237 AC97 Audio Controller (rev  
60) - onboard

Sorry guys, bit of a big one! Thanks in advance for any help on offer,

Ben