[mythtvnz] Audio levels significantly different across different channels

[Stephen Worthington]

On Fri, 06 Jun 2014 11:00:49 +1200, you wrote:

>Hi,
>
>I have noticed recently I now have to alter the TV volume when changing 
>channels which I don't recall having to do in the past to the same 
>degree as now. The audio levels seem to differ across channels, I 
>haven't done a full analysis yet, but Channel 4 seems significantly 
>louder than others.
>
>Apart from routine updates nothing has changed on my Mythbuntu setup, 
>however I did add a seocnd HDHomeRun device to increase the available 
>tuners. When adding the 2nd unit I did upgrade the firmware on the 
>original one.
>
>I was under the impression that all TV channels are broadcast with the 
>same audio levels, so would imply the problem is my end.
>
>Anyone got any thoughts as to what is happening and if there are 
>settings anywhere in MythTV to alter audio levels on a per channel basis 
>so I don't have to keep mucking around with the TV volume?
>
>Regards
>
>Chris Macneill

Some channels (the HD ones) have AC-3 5.1 audio as well as AAC audio.
My guess would be that you are seeing the difference when the audio is
AAC only, as Four is an SD channel and has only AAC.  If I am right,
ChoiceTV will likewise be too loud.  As best I can remember from when
I had this problem, AC-3 audio was always lower volume than AAC audio.

If you are not using the 5.1 channels, you can just use the AAC audio
and set the volume for that.  Or if you only need stereo, try turning
off the downmixer, and just use the front channels, if there is a way
to do that.  My feeling has always been that the quality of the AC-3
audio was better than the AAC, so if you can get it to work it is
better to use the AC-3 where it is available.

I use mediainfo to tell me what is in my recording files.  There is a
Ubuntu package for it.