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

[Ben Coleman]

Michael T. Dean wrote:
> On 05/09/2009 03:35 PM, Stefan Reichel wrote:
>> i have a little problem watching live tv. I use dvb-c, normally tv-shows
>> and commercials are transmitted with stereo sound, nevertheless some
>> movies will be broadcasted with AC3. In result when watching a movie
>> with ac3 sound volume is low, when the commercial begins, it gets stereo
>> and the sound volume raises dramatically.
>>
>> Is there any way to get rid of these volume problems?
>
> Get 5.1 speakers?
>
>>  Can i somehow
>> disable ac3 and convert it to stereo?
>
> If you're already doing 2-channel output (i.e. no AC-3/DTS passthrough 
> and you have the "Max Audio Channels" setting*** set to "Stereo"--not 
> "5.1"), it's already being done for you.
>
> If it /really/ concerns you, you can put a local hack in your own 
> build of Myth similar to http://svn.mythtv.org/trac/changeset/15526 , 
> but note that it will /not/ be applied to "upstream" as current ffmpeg 
> levels are appropriate.
>
> Mike
>
> ***In frontend settings under the main General settings section just 
> after the database settings on a page called, "Audio."

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.


BC.