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

[Michael T. Dean]

mike choy wrote:

>Paul V. Gratz wrote:
>  
>
>>Actually there is supposed to be a plugin for this in alsa called
>>"softvol".
>>
Wondered how long it would take for this to come up.

>> 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....
>>
>As a principle for sound quality you dont want to be resampling the vol 
>in the digital domain. You will drop quality as well as loose dynamic 
>range. Leave your AV amp to do this as it will do it in the analog 
>domain AFTER the DAC.
>  
>
Definitely true.  However, TTBOMK, the softvol plugin doesn't resample 
the signal for digital streams--it simply uses "dynamic range 
compression."  It's a much easier (less processor-intensive) adjustment, 
but not really any better--quality-wise--than resampling.  IMHO, it's 
kind of like cooking a steak in a toaster oven--it gets the job done, 
but it's definitely not the right tool for the job and you can get much 
better results using a different approach.

>The simple way to do all this is to use an Infrared remote. Programme up 
>the vol control on your remote to move the vol on your av amp only. 
>There's no need to change inputs or devices on your remote. Leave the 
>vol control on the computer side fixed.
>  
>
And, this is The Right Way (TM) to do it, too.  What I find astounding 
is the number of people who use digital for "better quality audio" and 
then do things like softvol.  One step forward, two steps back.  ;)

As a matter of fact, I don't expect to use digital connections for any 
of my audio.  I can't live without timestretch, anymore (thanks, 
Mark)--on TV and for DVD's--and decoding and re-encoding an AC-3 
(*lossy* compression algorithm) stream to allow timestretch seems like 
it negates the benefit of a digital audio connection.  After all, the 
audio is running over short connections and has to be analog between the 
receiver and the speakers, anyway, so proper wiring of analog 
connections will probably give at least as good--if not better--quality 
as resampled AC-3.

Mike