[mythtv-users] Volume is reduced during commercials

[Michael T. Dean]

On 08/20/2012 03:52 PM, Ray Parrish wrote:
> I have noticed a behavior similar to what the OP is describing:
>
> Step 1. Recording starts with AC-3 2ch audio, so MythTV renders a PCM
> 2ch stream to send through audio output
>
> NOTE: I have observed this behavior on my own setup by looking at the
> indicators on my a/v receiver. I have upmixing disabled and Dolby
> Digital Passthrough checked.
>
> Step 2. Somewhere in the recording (possibly in a commercial), the
> audio stream changes to 5.1ch. MythTV switches output to Dolby Digital
> 5.1
>
> Step 3. When the main program returns from commercial, audio output
> remains Dolby Digital, though 2-ch this time.
>
> I have noticed that the rendered PCM stream does seem "louder" than
> the same 2-ch audio passed through as AC-3.
>
> To the original poster, does this explanation appear to work with your
> observable information?

FWIW, MythTV (and, more specifically, ffmpeg libraries) doesn't support 
AC-3's dialnorm metadata parameter that provides playback gain 
information.  Therefore, when switching to/from AC-3, you're likely to 
have volume differences.

This is also why volume in the commercials on some channels is much 
louder (around here on my local (US) Fox, as one specific example).  
Currently the only workaround is the volume button.

Mike