[Pythonmac-SIG] getting/setting system volume in OS X with python?

[Robert Brown]

You could use Applescript to do it too.  But PyObjC is really a  
wonderful tool.


On 4-May-05, at 8:35 PM, Bob Ippolito wrote:

> On May 4, 2005, at 9:51 PM, Erik Osheim wrote:
>
>
>> I've been developing a curses-based music player in python for the
>> last couple of years (http://www.bearhome.net/mpy3) and it is getting
>> pretty good these days. I have added keybindings to control volume in
>> linux using the ossaudiodev module found in python.
>>
>> I wanted to do the same thing under OS X which I am now trying to
>> fully support. After some digging, it looked to me like Carbon.Snd  
>> was
>> the ticket. However, I can't find any documentation on this module; I
>> did some digging in Apple provided docs, and was able to get a
>> semi-working, semi-broken version of volume control going (mutes one
>> ear, controls the volume of the other), but I am not sure this  
>> will do
>> it.
>>
>> My questions are:
>>
>> 1. Does anyone have a good idea how to go about doing this best on OS
>> X? I am not going to be able to support OS 9 (too many unix
>> dependencies) so if there is a cleaner way to do it than Carbon I
>> would be interested.
>>
>
> The best way to do it on OS X is to use CoreAudio, but none of that
> is wrapped in Python.  You can, however, find an Objective-C
> framework that wraps what you need (MTCoreAudio should be able to do
> it, but there might be something easier) and just call into that with
> PyObjC.
>
> There are a couple other ways, but they're all really, really old and
> deprecated and they often behave pretty strangely.
>
>
>> 2. Is there anywhere to get better docs on things like ae*, Carbon.*,
>> etc? It seems like python for mac is incredibly powerful but arcane,
>> and between no documentation and no doc strings I have a hard time
>> figuring out what I can do with it.
>>
>
> The first thing you should do is look for another way to do it, with
> PyObjC or some POSIX API (but probably PyObjC).  There's a very
> straightforward translation between Objective-C and Python, so you
> use Apple's Cocoa docs when developing with PyObjC.
>
> If there is no way to do what you need with just PyObjC, you should
> consider just writing a little Objective-C wrapper that does what you
> need to do (calling into Carbon, CoreFoundation etc.), and call into
> that from PyObjC.  Use the Apple documentation.  Unfortunately this
> does require knowing C, but the ONLY documentation and the ONLY
> supported APIs are for C and Objective-C.  Most of the time, in my
> experience, it's just quicker to write and debug the code (i.e.
> QuickTime related stuff) in Objective-C and call into it from PyObjC.
>
> If you still feel the need to try and do it with "pure Python", then
> read the Apple documentation for the relevant function(s) in C, and
> then guess at how it would be done from Python.  Everything in
> Carbon.* is automatically generated, but there are a bunch of special
> cases and the rules are a bit strange.  These modules would sooner go
> away than become documented.  Don't be surprised if there's a bug in
> the wrapper or some function call sequence is impossible because the
> wrapper won't let you pass NULL somewhere, etc.  Writing code using
> undocumented modules that may be broken is no fun.
>
> -bob
>
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>

---------------------------------------------------
Robb Brown
Seaman Family MR Research Centre
Calgary, Alberta, Canada

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