change volume of single audio device

[moldevort87 at gmail.com]

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]

Could anyone tell me why this error occurs?