Audio Driver Registry Settings (Compact 2013)

3/26/2014

The following information describes the registry keys for ACM drivers and the software mixer.

[HKEY_LOCAL_MACHINE\Drivers\BuiltIn\CODEC_GSM610]
    "Prefix"="ACM" 
    "Dll"="gsm610.dll"
    "Index"=dword:1 
    "Order"=dword:0 

The Prefix registry value becomes part of the stream driver name when the Audio Driver Registry Settings function accesses this value.

The Dll registry value specifies the file name of the DLL containing the driver.

The Index registry value is appended to the stream driver name ACM1. If the value is not set, the Device Manager chooses a number.

The following registry key example shows the Order registry value and the load order of the driver.

[HKEY_LOCAL_MACHINE\Drivers\BuiltIn\FILTER]
    "Prefix"="ACM"
    "Dll"="msfilter.dll"
    "Index"=dword:2
    "Order"=dword:0

[HKEY_LOCAL_MACHINE\Audio\SoftwareMixer]
    "SampleRate"=dword:AC44
    "Buffers"=dword:4
    "BufferSize"=dword:800
    "EnableLowPassFilter"=dword:1
    "Priority 256"=dword:dc

The SampleRate registry value specifies the sample rate, measured in samples per second, that the software mixer uses when opening the audio device. The default is 0xAC44, which is equivalent to a decimal value of 44100.

The Buffers registry value specifies the number of buffers that is used in the software mixer audio stream. The default is 4.

The BufferSize registry value specifies the size, measured in bytes, of the buffers that is used in the software mixer audio stream. The default is 0x800, which is equivalent to a decimal value of 2048

The EnableLowPassFilter registry value controls whether the software mixer applies a low pass filter when conducting sample rate conversion. Low-pass filtering improves audio quality at the expense of the CPU overhead. The default is 1, which means the low pass filter is enabled.

The Priority 256 registry value specifies the thread priority at which the software mixer will run.

[HKEY_LOCAL_MACHINE\Drivers\BuiltIn\WaveDev]
    "Prefix"="WAV"
    "Dll"="wavedev.dll"
    "Index"=dword:1
    "Order"=dword:0
    "IClass"="{E92BC203-8354-4043-A06F-2A170BF6F227}"; DEVCLASS_WAVE_GUID

The Prefix registry value becomes part of the stream driver name when the Audio Driver Registry Settings function accesses this value.

The Dll registry value specifies the file name of the DLL containing the driver.

The Index registry value is appended to the stream driver name WAV1. If the value is not set, the Device Manager chooses a number.

The IClass registry value advertises a waveform device interface.

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