AAM_FilterControl

This function allows control of the digital crossover filter parameters.

Syntax

DWORD AAM_FilterControl ( DWORD dwFlags, DWORD *plEnable, DWORD *plFreq );

Parameters

dwFlags

Specifies a bitmask of flags. It is one of the following values:

AAM_FLAG_CROSSOVER_LPF

Combine with AAM_FLAG_SET to enable, disable, and set the frequency of the low-pass filter (LPF). Combine with AAM_FLAG_RANGE to get the range of LPF frequencies that may be set.

AAM_FLAG_CROSSOVER_HPF

Combine with AAM_FLAG_SET to enable, disable, and set the frequency of the high-pass filter (HPF). Combine with AAM_FLAG_RANGE to get the range of HPF frequencies that may be set.

AAM_FLAG_CROSSOVER

Combine with AAM_FLAG_SET to enable, disable, and set the frequency of crossover frequencies (LPF and HPF). Combine with AAM_FLAG_RANGE to get the range of crossover frequencies that may be set. This flag is for use in implementations that do not support separate control of the high-pass and low-pass filter.

AAM_FLAG_GET

When combined with a filter flag, retrieves the current filter settings. The enabled status of the filter is returned in plEnable and current frequency is returned in plFreq.

AAM_FLAG_RANGE

When combined with a filter flag, retrieves the range over which the frequency can be set, and indicates whether or not the filter can be enabled or disabled. The following table shows the information returned in the plEnable parameter.

Low-order word	High-order word	Description
0	0	No such filter available
Nonzero	0	Filter is available and can be enabled or disabled.
Nonzero	Nonzero	Filter is available and is always enabled.

The following table shows the information returned in the plFreq parameter.

Low-order word	High-order word	Description
Maximum adjustable frequency, in hertz.	Minimum adjustable frequency, in hertz.	Specifies the frequency range.

AAM__FLAG_SET

When combined with a filter flag, allows you to enable, disable, and set the frequency of the filter.

plEnable

Pointer to a DWORD used to return or set whether or not the filter is enabled.

plFreq

Pointer to a DWORD used to return or set the frequency.

Return Values

Zero indicates success. AAM_ERR_INVALIDPARAM indicates an invalid parameter. AAM_ERR_NOTSUPPORTED indicates a filter or action is not supported in a particular implementation. AAM_ERR_OUTOFRANGE indicates a requested frequency value was not in the valid range of the filter.

Remarks

Do not set both the AAM_FLAG_SET and AAM_FLAG_RANGE flags.