[mythtv] [mythtv-commits] Ticket #7517: Separate Volume control from Audio Output

Ed W lists at wildgooses.com
Mon Aug 16 21:46:02 UTC 2010


>> Another thing that I added (way back when) with a hope that someone 
>> would pour sauce on it was the "AudioOutputSource" param when you 
>> open the audio device (TV/Video/Music/Phone/etc)?  The idea was that 
>> the volume control might have a per application memory and make use 
>> of this when different applications open the audio device?  I think 
>> it's been treated as a dead parameter since then, but it would be 
>> really nice if someone would pick it up and consider using it for 
>> something?  (there seem to be some tentative re-implementations of 
>> this feature starting to happen already causing some code 
>> duplication?)  See audiooutputsettings.h
>
> I consider that problem to be more one of "mixing" rather than 
> "volume" control. The implementation I propose solely aims to provide 
> a "volume" control, namely a means of adjusting the overall audio 
> output level. Balancing the levels of different audio sources, or 
> channels is a relatively infrequent operation requiring a considerably 
> more complex user interface that is best placed within the 
> setup/configuration screens. The interface for controlling the volume 
> should be as simple as possible (increase/decrease/mute).

I think you misunderstand my point - at the moment we track only a 
single "volume" level, and there is then a bunch of hard-coded level 
adjustment for music/tv/video.  I was just pointing out that we know 
what the application wants to be doing, so we could actually track 
volume per application.  Eg if I leave the TV on max volume and music on 
really low then it's still like that when I switch back to each.  
Turning up the volume in the music app doesn't mean it gets louder if we 
switch to TV

Anyway, there are probably other things we could use this field for.  As 
you say there could be a "balance" feature added somewhere or other 
exotic stuff (personally I don't see the point of a "balance", but 
others might?)


> So, for example, there is little benefit from using Jack's software 
> volume implementation as MythTV already provides its own software 
> volume control.
>

When I looked some weeks ago there was a small issue in that the volume 
was applied when buffering the audio, not when it's fed to the 
soundcard.  This means that there is a very long delay before adjusting 
the volume actually affects what comes out of the speakers.

It can obviously be rectified, but it's currently quite a big difference 
in implementation between the two at the moment?

Cheers

Ed W


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