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Re: [ANNOUNCE] New Mixer Handling in PA 0.9.16/F12



On Thu, Jul 30, 2009 at 04:53:25PM -0500, Matthew Woehlke wrote:
> Doug Ledford wrote:
>> Every system I build still keeps the analog signal cable between the
>> CD/DVD and the soundcard. This doesn't help if I try to watch a movie
>> as that signal has to be decoded and then played, but for audio CDs
>> it is still a perfectly acceptable means of playing the music. So I'm
>> not sure where this "CD in is obsolete" comes from. Even the
>> motherboard I bought about 2 months ago still has a CD in port and
>> the CD/DVD in that machine still has an analog output.
>
> CD is digital and can be read in digital format by your CPU and sent in  
> digital to the sound device. This is lossless.
>
> You want to:
> (D->A) do the DAC in the CD drive
> (A) toss that on an analog wire
> (A/A->D->A) apply an analog volume adjustment (if you're lucky; you  
> might actually end up doing a ADC, digital volume adjustment, DAC)
> (A/A->D) toss that on a different wire that might be digital
> (A/D->A) hear it from your speakers
>
> You could:
> (D) read the CD digital data
> (D) toss said data to the sound device (losslessly!)
> (D/D->A) apply a digital volume adjustment (or maybe analog volume  
> adjustment after DAC)
> (D/D->A) send that, maybe digitally, to your speakers
> (A/D->A) hear it from your speakers
>
> What exactly is better about the first scenario? At *best* you're moving  
> the analog signal across a longer run of wire (and one that is inside  
> your computer case with who-knows-what shielding picking up  
> who-knows-what interference). At worst you've tossed several analog  
> elements into a process that could have been digital from disc to  
> speaker cones.
>
> Seriously... do I miss something?

That reading in the data digitally uses non trivial amounts of PCI and
CPU bandwidth.  If I can't hear the difference between the two modes,
then that CPU usage is a total waste of resources.  I have other things
I want my CPU to be doing.


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