[mythtv-users] Intermittent glitchy audio in Live TV

Brent Meyer brent.meyer at gmail.com
Sat Jun 26 17:49:03 UTC 2010

Occasionally, when changing channels in Live TV, the audio becomes
horribly glitchy and distorted. See this clip for an example:
http://www.youtube.com/watch?v=lnSvigWEa-o (warning: make sure your
volume is not all the way up)

Here is a log from one of these playback events (running mythfrontend
-v audio): http://pastebin.com/2KcnUg9Q

On the backend, I have two Comcast Pace DTAs connected to a PVR250 by
way of a channel 3/4 combiner. I know the combiner is not the issue,
because I had the same issue when only one DTA was connected to the
PVR250, sans combiner.

My frontend machine is an early 2009 Mac mini. I'm running Mythbuntu
10.04 with Myth .23, though this problem has existed since about Myth
.21 (it's just getting worse now).

My backend also has a couple of HD tuners, and audio always plays back
perfectly when watching live HD. The problem only occurs when watching
non-HD content via the Pace DTAs.

Finally--and this is the part that seems weird to me--this distortion
never occurs in recorded programs. It only occurs when changing
channels in Live TV.

Audio Settings:
- Audio output device: ALSA:spdif
- Speakers configuration: 5.1
-- Upconvert stereo to 5.1 sound: Checked (doesn't seem to make a
difference whether or not this is checked)
-- Upmix: Good
-- Digital output device: ALSA:iec958:{ AES0 0x02 }
-- Dolby Digital: Checked (receiver supports DD)
-- DTS: Checked (receiver supports DTS)

Other settings:
- Playback Profiles: VDPAU Normal
- Extra audio buffering: Checked (doesn't seem to make a difference)

Has anybody experienced anything similar? And can anybody think of a
solution? If it weren't for this WAF-killer, I could dump our cable
boxes and save a few dozen dollars per month.

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