[mythtv-users] Volume problems watching live-tv (ac3 vs. stereo)

Stefan Reichel stefan.reichel at rapid-net.de
Wed May 20 18:02:52 UTC 2009


first of all thank you for your replies.

MtDean posted a patch to boost the audio volume when using ac3 by factor
3(http://svn.mythtv.org/trac/changeset/15526). I tried to apply this
patch to the current svn version by editing " libs/libavcodec/ac3dec.c".
Nevertheless the code has evolved and therefore the patch/hint couldn't
be applied by myself.

How can i achieve the suggested audio boost in the new code? 



On Wed, 2009-05-20 at 16:03 +1000, Ben Coleman wrote:
> Ben Coleman wrote:
> > Whilst I went back to not having AC3 on my stereo (preamp went in for 
> > repair) I had to fiddle with it and also alter mplayer settings to 
> > allow 2channel normalisation.
> >
> > This involved tweaking alsa-mixer to ensure I was downsampling to 2ch, 
> > and adding oss function to the mplayer via the command line. Check out 
> > alsamixer and see what options are enabled in there.
> >
> > As I was passing AC3 through etc, and I had no decoder for AC3 
> > anymore, I didn't want to play around too much with AC3 as it took 
> > long enough to get it working under my scenario. I was experiencing 
> > the same issue whilst my preamp was being repaired and this tweaking 
> > seemed to fix the problem.
> >
> > I'm sorry I can't be more specific but I didn't write down what I did 
> > .. just remembered that I altered it through alsamixer to ensure it 
> > was outputting a 2channel signal from the source.
> I have my newer preamp back and still have the same problem as the 
> original poster. I use ac3 passthrough as I did with 0.20 and I have 
> muffled sound for ac3 streams.
> I figure this to be either an alsa issue or mythtv configured 
> inocrrectly, but am lost and interpreting what I should and should not 
> do. There are settings in myth to 'use' spdif for ver 0.21. When I use 
> it, it DOESN'T work. When I use default, it does work. NOTE: I am using 
> SPDIF for audio output to my preamp which processes the AC3 signal.
> Can anyone suggest how to faultfind this issue?
> Regards,
> BC
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