[mythtv-users] SPDIF audio dropouts

jonny Linux jonnylinux at gmail.com
Tue May 10 11:10:05 UTC 2011


Hi all,

I've just had to rebuild a frontend. Everything apart from the
motherboard and processor (AMD Athlon II X2 250 3GHz) is the same as
it was before.

I then installed 64-bit Ubuntu 11.04 (I had a 32 bit system before).
I'm using a NVidia 8400GS, with the latest drivers (although I have
tried other drivers too). I'm using DVB-T (UK). The soundcard is a
CMI8738 chipset, and it's connected to my amplifier using S/PDIF
optical.

I'm now getting a lot of silent audio gaps (video carries on), lasting
around 0.5 - 2 seconds each time, so I'm missing about 1-2 words every
10 seconds. I'm using ALSA:hw:CARD=CMI8738,DEV=0 for my output device.
I've also occassionally had this problem when when playing ogg files
in mplayer (but mplayer seems more reliable).

I've also checked the CPU usage, CPU is fairly consistently at about
20%, there are no CPU spikes coinciding with the dropouts. I've looked
in the log (with -v audio,playback), the only thing I can see is:

ALSA: Requested 500000us got 341333 buffer time
ALSA: Hardware audio buffer cur: 64 need: 128 max allowed: 128
ALSA, Error: Setting hardware audio buffer to 128

I've tried with and without VDPAU, I get the same problem either way.
If I play a DVD, the audio works perfectly, so I suppose the DTS
passthrough must be working?

I wondered if it was anything to do with the 64-bit drivers, so I
installed the 32 bit version, but that has the same problem.

Can anyone help please?

Thanks,

Jonny


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