[mythtv-users] Distorted sound from 6ch AC3 in HD3000 recordings

Joseph Fry joe at thefrys.com
Fri Dec 17 18:32:45 UTC 2010

> At first listen, the distortion sounds to me maybe a bit like clipping, but
> then listening closer, it sounds more like a soft crackly rapid-fire popping
> sound.  I guess it could even be tiny gaps in the audio, from just the sound
> of it.  In any case, it makes the recordings somewhat painful to watch, as
> I'm sure you can imagine.
> The recording files sound fine in mplayer, as well as in mythfrontend on
> different hardware.  Additionally, my SD recordings (PVR350) and downloaded
> videos of other audio formats all sound perfectly fine in myth.
> Here's a log from "mythfrontend -v audio,playback":
> http://westbrook.com/mythfrontendlog20101217a.log
I am certainly no expert, but these lines look suspiciouis:
2010-12-17 10:14:09.558 ALSA: Requested 200000us got 92879 buffer time
2010-12-17 10:14:09.558 ALSA, Error: Error opening
/proc/asound/card0/pcm0p/sub0/prealloc. Fix reading permissions.
2010-12-17 10:14:09.558 ALSA, Error: Unable to sufficiently increase
preallocated buffer size - underruns are likely

Maybe try something like "echo 1024 | sudo tee
/proc/asound/card1/pcm0p/sub0/prealloc" to set the prealloc up to a better
level and see if it fixes playback?

Toward the end of this thread:
http://forums.whirlpool.net.au/archive/1445975 (starting december 11th) they
start discussing that error.... might be a good read.
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