[mythtv-users] AC3 and/or S/PDIF (again)

[Paul V. Gratz]

On Sunday 22 January 2006 08:29 am, Ben Suffolk wrote:
> 
> > > No, Ben, I don't. And, as I understand it, this is impossible. Since
> > > we're just passing through a digital signal to the receiver, it's  
> > all up to
> > > the receiver to deal with it. In order to change the volume, we  
> > would need
> > > to decode the audio, sample down the volume, reencode it, then  
> > pass it on
> > > to the receiver. Maybe it's possible, but it certainly is not very
> > > efficient. And, by the way, this is all just speculation. I don't  
> > really
> > > know how it works, but my explanation made sense to me.
> >
> > And your explanation is more or less correct. If you're passing raw  
> > digital
> > audio, its completely raw, you can't controll its volume level.  
> > Might be best
> > to let Myth do the audio decoding and pass PCM audio instead of raw  
> > digital
> > audio. Could also try to rig up something with an irblaster if  
> > you're dead
> > set on having the amp in a different room and passing raw audio.
> >
> > -- 
> > Jarod Wilson
> > jarod[at]wilsonet.com
> 
> I though this might be the case, I have to say I don't really know  
> about digital audio, but I had hoped that maybe it would be quite  
> easy to manipulate it in the digital realm, so not having to convert  
> it, just simply dividing each digital value by the volume level. I  
> guess not.
> 
> I thought maybe I could use an irbalster to swap the inputs on my amp  
> between regular 2 channel pcm for tv and music, then have it auto  
> switch to 5.1 when you play a dvd, and then switch back again for TV.  
> I guess this could be done quite easily with a shell script set as  
> the player for the dvd & video playback. Not idea, but would allow  
> the osd for volume in TV etc.
> 
> Ben


Actually there is supposed to be a plugin for this in alsa called
"softvol". Check out the bottom of this page:

http://www.alsa-project.org/alsa-doc/alsa-lib/pcm_plugins.html

I messed with it for a while but I've been unable to figure out how to
make it work....
Paul


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