change volume of single audio device

[Jean-Michel Pichavant]

----- Original Message -----
> hi,
> 
> i'd like to change the volume of my av-receiver (HDMI) and speakers
> (analogue) simultaneously. in order to use both outputs i'm using
> virtual audio cable but if i set it as default device and change
> volume, hdmi and analogue remains unchanged.
> i intend to script a command line tool in python providing to change
> the volume of a single device (eg "setvolume {deviceID} {volume}")
> 
> i've been looking for a similar tool, but none of them worked (eg
> nircmd); i'm using Win7.
> 
> while looking for a solution i found that snippet of code
> 
> [CODE]
>     #!/usr/bin/env python
>     #Boa:PyApp:main
>     modules = {}
>      
>     import ctypes
>      
>     mixerSetControlDetails = (
>         ctypes.windll.winmm.mixerSetControlDetails)
>      
>     mixerGetControlDetails = (
>         ctypes.windll.winmm.mixerGetControlDetailsA)
>      
>     # Some constants
>     MIXER_OBJECTF_MIXER = 0 # mmsystem.h
>     VOLUME_CONTROL_ID = 0     # Same on all machines?
>     SPEAKER_LINE_FADER_ID = 0 # "Identifier <identifier> in OID value
>     does not resolve to a positive integer"
>     MINIMUM_VOLUME = 0     # fader control (MSDN Library)
>     MAXIMUM_VOLUME = 65535 # fader control (MSDN Library)
>      
>     class MIXERCONTROLDETAILS(ctypes.Structure):
>         _pack_ = 1
>         _fields_ = [('cbStruct', ctypes.c_ulong),
>                     ('dwControlID', ctypes.c_ulong),
>                     ('cChannels', ctypes.c_ulong),
>                     ('cMultipleItems', ctypes.c_ulong),
>                     ('cbDetails', ctypes.c_ulong),
>                     ('paDetails', ctypes.POINTER(ctypes.c_ulong))]
>      
>     def setVolume(volume):
>         """Set the speaker volume on the 'Volume Control' mixer"""
>         if not (MINIMUM_VOLUME <= volume <= MAXIMUM_VOLUME):
>             raise ValueError, "Volume out of range"
>         cd = MIXERCONTROLDETAILS(ctypes.sizeof(MIXERCONTROLDETAILS),
>                                  SPEAKER_LINE_FADER_ID,
>                                  1, 0,
>                                  ctypes.sizeof(ctypes.c_ulong),
>                                  ctypes.pointer(ctypes.c_ulong(volume)))
>        
>         ret = mixerSetControlDetails(VOLUME_CONTROL_ID,
>                                      ctypes.byref(cd),
>                                      MIXER_OBJECTF_MIXER)
>        
>         if ret != 0:
>             print WindowsError, "Error %d while setting volume" % ret
>      
>         ret = mixerGetControlDetails(VOLUME_CONTROL_ID,
>                                      ctypes.byref(cd),
>                                      MIXER_OBJECTF_MIXER)
>         if ret != 0:
>             print WindowsError, "Error %d while setting volume" % ret
>         else:
>             print 'cbStruct', cd.cbStruct
>             print 'dwControlID', cd.dwControlID
>             print 'cChannels', cd.cChannels
>             print 'cMultipleItems', cd.cMultipleItems
>             print 'cbDetails', cd.cbDetails
>             print 'paDetails', cd.paDetails.contents
>         return
>      
>     setVolume((2**16-1)/2)
>      
>     from ctypes import *
>     from struct import *
>      
>     winmm= windll.winmm
>     print
>     print 'waveOutGetNumDevs=',winmm.waveOutGetNumDevs()
>     print 'mixerGetNumDevs', winmm.mixerGetNumDevs()
>      
>     wvcps= ' '*52
>     print 'res:', winmm.waveOutGetDevCapsA(0,wvcps,len(wvcps))
>      
>     res = unpack('IIL32cLI', wvcps)
>     wMid=res[0]
>     wPid=res[1]
>     vDriverVersion=res[2]
>     szPname=''.join(res[3:35])
>     dwFormats=res[35]
>     wChannels=res[36]
>     print 'wMid=',wMid
>     print 'wPid=',wPid
>     print 'vDriverVersion=',vDriverVersion
>     print 'szPname=',szPname
>     print 'dwFormats=',dwFormats
>     print 'wChannels=',wChannels
>      
>     vol=c_ulong()
>     print 'res', winmm.waveOutGetVolume(0, byref(vol))
>      
>     print 'l:', vol.value & 0xffff, 'r:',vol.value >> 16 # left,
>     right
> [/CODE]
> 
> 
> on executing i get
> [CODE]
>     <<type 'exceptions.WindowsError'> Error 11 while setting volume
>     <type 'exceptions.WindowsError'> Error 11 while setting volume
>      
>     waveOutGetNumDevs= 3
>     mixerGetNumDevs 4
>     res: 0
>     wMid= 6553601
>     wPid= 1537
>     vDriverVersion= 2037083727
>     szPname= o (AMD High Definition Audi
>     dwFormats= 2
>     wChannels= 36
>     res 0
>     l: 65535 r: 0
> [/CODE]
> 

I'm afraid there's nothing related to python here.
It looks like the win function mixerSetControlDetails returned the error MMSYSERR_INVALPARAM.
You've set your devices IDs to 0. Are you sure this is correct ? 


Cheers,


JM


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