Re: Re: [PATCH] Add support for Acer TravelMate and

[Rimas Kudelis <rq@akl.lt>]

Jonathan Woithe wrote:
>>> The "CD" input on the ALC260 is an analog input.  It expects the CD drive to
>>> do all the audio decoding and present an ordinary stereo signal to this pin. 
>>> If when playing a CD and enabling the "CD" control you get no audio that
>>> strongly suggests that there is no audio signal running to that pin.
>>> However, if there is no analog connection to the ALC260 one does wonder
>>> precisely how these systems are expected to play CDs.  The only option 
>>> left would be for software to read the raw CD bitstream (which isn't a straight
>>> audio bitstream), decode it and then send the resulting audio bitstream to
>>> the DAC.  Given that CD drives are more than capable of doing all this it would
>>> surprise me if this were the case.
>>>
>>> One thing worth checking though - have you tested *all* ALC260 inputs with
>>> the CD playing?  Maybe Acer connect the CD audio to some other ALC260 pin. 
>>>       
To be honest, I haven't. I thought the CD pin is a bit different from
the others, so I didn't bother to test everything.

>> I would not be surprised if some vendors were leaving out the DAC from
>> their CD drives, and expect you to play audio CDs in digital mode.  I
>> believe this is how Windows Media Player works by default (it also
>> allows it to generate visual effects from the CD audio).
>>     
> Ah, right.  I wasn't aware of that.  If that's its default behaviour then
> perhaps the Acers do expect the OS to use digital mode for playing CDs. If
> this proves to be the case then we'll revise the "acer" model to omit the CD
> controls.
I believe the Gnome CD player and Sound Juicer applications do that too.
I think they, just like all other Gnome apps, use the Gstreamer
framework. And I can even see a reason for that - most soundcards only
have one set of pins for a CD (i.e. only one cd channel) meanwhile many
new desktops come with two CD drives. Add to this what Lee has
mentioned, and you get quite a set of reasons to use software to extract
audio.

Rimas



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