[mythtv-users] Digital audio: centre channel drops out intermittently

Marc Sherman msherman at projectile.ca
Sat Jan 21 13:42:48 UTC 2012


On 1/21/2012 7:27 AM, Dave Badia wrote:
> I seem to be having the same issue while running the latest 24 fixes.
> This happens regularly during the ABC world news which I record via
> OTA on my hdhr.  Audio starts as 6 channels, but somewhere in the
> first commercial break, the center channel drops out.  It then comes
> back after the 2nd commercial break.  I have -v audio,playback
> enabled, but there's nothing unusual in the logs when the audio
> changes.  I can reproduce it by skipping ahead and back.  I checked
> the last 2 nights recordings and they both show the same behavior - my
> wife says it's been like that for awhile.  I'm in the process of
> compiling the latest jyavenard/backports/fixes/0.24 branch to see if
> how that behaves.

Interesting, glad to hear I'm not alone in this. Is it exactly 
reproducible for you? That is, if you rewind over the dropout, does it 
always drop out and come back in at exactly the same moment? In my case, 
it doesn't -- it'll drop out around the same area, but not on the same 
frame every time.

Also, for me, in some recordings it's more reproducible than others. 
I've got a recording of Family Guy from WUTV last week where it happens 
around the 2:15 mark (give or take) pretty much 100% of the time, but 
last week's SNL from CIII was very intermittent -- the second time I 
watched it hoping to collect data about the failure, it didn't happen at 
all.

Would you be willing to try out my recording of family guy to see if you 
get the same problem with it?

Anecdotally, I _think_ the frequency of the problem depends on the 
channel, so it might have something to do with the way the channel is 
encoding their OTA broadcasts -- I think I notice it most often on WUTV 
recordings. But I don't have stats to back that up, so I might have 
imagined it. I don't think it's related to reception -- despite being in 
Buffalo while I'm in Toronto, WUTV is one of the stronger channels I get.

- Marc


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