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

Ben Suffolk ben at vanilla.net
Sun Jan 22 14:29:31 UTC 2006

> > 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.


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