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

Marc Sherman msherman at projectile.ca
Thu Jan 26 02:49:49 UTC 2012


On 1/24/2012 8:16 PM, Dave Badia wrote:
> I tested against the jyavenard/backports/fixes/0.24 branch and the
> audio dropout still occurs.  I then tried playing the same clip
> through mplayer and it happened there as well.  I suppose that points
> to a problem with the broadcast itself but I'm really not sure how to
> check that.

Hey, thanks for the tip, Dave. Playing the same mpg through mplayer is 
exactly what I needed to isolate the problem and confirm that it's _not_ 
a mythfrontend bug -- I also get the same problem when I play this movie 
in mplayer with -ac hwac3.

Am I correct in thinking that there's no way this is being caused by my 
sound card? With the mpg's AC3 track being passed through unmodified 
straight to the amp over SPDIF, any bug in the sound card would corrupt 
the entire audio, not just the center channel, right?

So I guess the next step is to go buy a new amp, and spend the first two 
weeks while I can still return it trying to replicate the problem with 
the same track. If I can't, then it was my amp dying, and I keep the new 
one. If I can replicate it with a new amp, then I guess the problem must 
be in the way the recordings are being encoded by the tv station? At 
which point I return the new amp, write a letter to the tv station's 
engineering department, and switch mythtv to 2 channel audio 
permanently, I guess.

> Marc - sure, if you give me a clip I can test it here to see if I can
> reproduce it

Thanks for the offer, but now that I've proven mythfrontend isn't at 
fault here, I don't think it's worth it for you to download a 2G 
recording. I tried cutting the clip down to just a couple minutes with 
mencoder, but that version of the clip couldn't replicate the problem 
for some reason.

- Marc


More information about the mythtv-users mailing list