Re: [Audacity-devel] Win 7 mixer

[Martyn S. <mar...@go...>]

On 26/01/2010 02:01, Al Dimond wrote:
> On Monday 25 January 2010 18:15:53 Martyn Shaw wrote:
>> Hi Al
>>
>> On 25/01/2010 03:45, Al Dimond wrote:
>>> On Sunday 24 January 2010 17:28:22 Martyn Shaw wrote:
>>>> OK, so I know this has been discussed but I didn't have 7 so I
>>>> paid little attention.  Please point me to threads / wike
>>>> entries.
>>>>
>>>> Clearly (on 7) the Audacity volume control does not do what it
>>>>    should, that is it does not control the output volume of
>>>> Audacity but controls the overall volume of any audio being
>>>> played.  We need to fix that.
>>>>
>>>> I know that it used to do one thing and now needs to do another,
>>>>    and that is the 7 way.
>>>>
>>>> Pointers to posts would be useful.
>>>
>>> I posted a while ago about giving users a choice here. Apparently
>>> some people don't want any digital scaling before the signal hits
>>> the hardware mixer. Other people really don't want the volume in
>>> other programs to be affected by Audacity's volume.
>>
>> I think those demands are inconsistent in XP and earlier.  Unless
>>   all values are passed as float/double, and then it's a matter of
>>   processer overheads.  Both 'should' be possible in 7 (from my
>>   reading) by leaving it to the OS there.
>>
>> Possibly your suggestion of a choice/pref was prompted by this
>> impossibility?
>>
>
> Yes, exactly. We can't satisfy both types of users at the same time.

Good, we understand each other.  But they aren't 'types of users' they 
are 'users on different OSs' aren't they?

We recently had some Win 7 specific inclusions in 
FileDialogPrivate.cpp.  Wouldn't that be a better way forward?  Making 
run-time decisions depending on the OS?

>> I can't work on Windows
>>
>>> audio stuff yet, but I have something that's just about ready
>>> that adds a choice on the device prefs screen (patch attached).
>>> It just uses the existing volume emulation for SW control.
>>
>> I'm not happy with emulation, since I believe it compromises SNR
>> (assuming fixed points are being passed to the next stage, it's
>> probably OK for quality with float/double but uses processor time)
>> (more I need to read up on).  If it has to be that way for XP then
>>   so be it.  I think that XP and 7 vary in this respect.
>>
>
> Volume emulation is done on the floats we're about to send to PortAudio
> (it's in audacityAudioCallback(), AudioIO.cpp). I'm not sure how
> Windows would do better than Audacity's emulation in terms of SNR --
> it has to be done in software, and they can't possibly have cleaner
> data than we have (they probably still have 32-bit floats at that
> point).

True.  And thanks for that info about floats being passed.  Win won't 
then do better (or worse, presumably) than us.  So why should we code 
it?  Let the OS do it for us, I say.

TTFN
Martyn

> Anyway, the appearance of per-app volume sliders in the Windows sound
> control panel doesn't change the fact that we have two groups of users
> that we can't satisfy at the same time.
>
>   - Al
>
>> TTFN
>> Martyn
>>
>>> The problem with giving the user a choice is that it complicates
>>> things. The way I see it, the logic should be:
>>>
>>>    - User wants hardware control: Try to open the PCM slider with
>>> PortMixer, fall back to disabling the mixer toolbar slider.
>>>    - User wants control of just Audacity: Try to open a system
>>> per-app slider with PortMixer, fall back to AudioIO's
>>> "emulation".
>>>
>>> One of these days we'll get real PulseAudio support and we'll be
>>> able to grab a per-app slider for Pulse... so it might be good to
>>> add a function to get our per-app slider to the PortMixer API (if
>>> it turns out that Win7 and PulseAudio name the per-app sliders
>>> differently).
>>>
>>>    - Al
>>>
>>>> Thanks
>>>> Martyn
>>>>
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