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

Ben Coleman arrikhan_mail at yahoo.com.au
Sun Jun 7 07:24:18 UTC 2009

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

I've fixed this issue. After reading through post upon post on the issue 
of AC3 tracks playing too softly, I changed various combinations of of 
the audio settings for hours and it now works.

In the end, one setting which I thought to not be involved in such a 
problem was the one setting that fixed it. All the rest were as I had 

I altered the UPMIX from ACTIVE to PASSIVE, originally thinking it would 
not possibly cause such a  problem as this, but when it comes to 
understanding what one field ACTUALLY means under the covers (beyond the 
description which only talks about processor usage) .. it can mean 

Anyway .. thought I would share.



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