MIXERCONTROL
The MIXERCONTROL
structure describes the state and metrics of a single control for an audio
line.
typedef struct {
DWORD
cbStruct;
DWORD
dwControlID;
DWORD
dwControlType;
DWORD
fdwControl;
DWORD
cMultipleItems;
CHAR szShortName[MIXER_SHORT_NAME_CHARS];
CHAR szName[MIXER_LONG_NAME_CHARS];
union {
struct
{
LONG lMinimum;
LONG lMaximum;
};
struct
{
DWORD dwMinimum;
DWORD dwMaximum;
};
DWORD
dwReserved[6];
} Bounds;
union {
DWORD
cSteps;
DWORD
cbCustomData;
DWORD
dwReserved[6];
} Metrics;
} MIXERCONTROL, *PMIXERCONTROL, FAR *LPMIXERCONTROL;
Members
cbStruct
Size, in
bytes, of the MIXERCONTROL structure.
dwControlID
Audio mixer-defined
identifier that uniquely refers to the control described by the MIXERCONTROL
structure. This identifier can be in any format supported by the mixer device.
An application should use this identifier only as an abstract handle. No two
controls for a single mixer device can ever have the same control identifier.
dwControlType
Class of the
control for which the identifier is specified in dwControlID. An
application must use this information to display the appropriate control for
input from the user. An application can also display tailored graphics based on
the control class or search for a particular control class on a specific line.
If an application does not know about a control class, this control must be
ignored. There are eight control class classifications, each with one or more
standard control types:
MIXERCONTROL_CT_CLASS_CUSTOM
MIXERCONTROL_CONTROLTYPE_CUSTOM
MIXERCONTROL_CT_CLASS_FADER
MIXERCONTROL_CONTROLTYPE_BASS
MIXERCONTROL_CONTROLTYPE_EQUALIZER
MIXERCONTROL_CONTROLTYPE_FADER
MIXERCONTROL_CONTROLTYPE_TREBLE
MIXERCONTROL_CONTROLTYPE_VOLUME
MIXERCONTROL_CT_CLASS_LIST
MIXERCONTROL_CONTROLTYPE_MIXER
MIXERCONTROL_CONTROLTYPE_MULTIPLESELECT
MIXERCONTROL_CONTROLTYPE_MUX
MIXERCONTROL_CONTROLTYPE_SINGLESELECT
MIXERCONTROL_CT_CLASS_METER
MIXERCONTROL_CONTROLTYPE_BOOLEANMETER
MIXERCONTROL_CONTROLTYPE_PEAKMETER
MIXERCONTROL_CONTROLTYPE_SIGNEDMETER
MIXERCONTROL_CONTROLTYPE_UNSIGNEDMETER
MIXERCONTROL_CT_CLASS_NUMBER
MIXERCONTROL_CONTROLTYPE_DECIBELS
MIXERCONTROL_CONTROLTYPE_PERCENT
MIXERCONTROL_CONTROLTYPE_SIGNED
MIXERCONTROL_CONTROLTYPE_UNSIGNED
MIXERCONTROL_CT_CLASS_SLIDER
MIXERCONTROL_CONTROLTYPE_PAN
MIXERCONTROL_CONTROLTYPE_QSOUNDPAN
MIXERCONTROL_CONTROLTYPE_SLIDER
MIXERCONTROL_CT_CLASS_SWITCH
MIXERCONTROL_CONTROLTYPE_BOOLEAN
MIXERCONTROL_CONTROLTYPE_BUTTON
MIXERCONTROL_CONTROLTYPE_LOUDNESS
MIXERCONTROL_CONTROLTYPE_MONO
MIXERCONTROL_CONTROLTYPE_MUTE
MIXERCONTROL_CONTROLTYPE_ONOFF
MIXERCONTROL_CONTROLTYPE_STEREOENH
MIXERCONTROL_CT_CLASS_TIME
MIXERCONTROL_CONTROLTYPE_MICROTIME
MIXERCONTROL_CONTROLTYPE_MILLITIME
fdwControl
Status and
support flags for the audio line control. The following values are defined:
MIXERCONTROL_CONTROLF_DISABLED
The control
is disabled, perhaps due to other settings for the mixer hardware, and cannot
be used. An application can read current settings from a disabled control, but
it cannot apply settings.
MIXERCONTROL_CONTROLF_MULTIPLE
The control
has two or more settings per channel. An equalizer, for example, requires this
flag because each frequency band can be set to a different value. An equalizer
that affects both channels of a stereo line in a uniform fashion will also
specify the MIXERCONTROL_CONTROLF_UNIFORM flag.
MIXERCONTROL_CONTROLF_UNIFORM
The control
acts on all channels of a multichannel line in a uniform fashion. For example,
a control that mutes both channels of a stereo line would set this flag. Most
MIXERCONTROL_CONTROLTYPE_MUX and MIXERCONTROL_CONTROLTYPE_MIXER controls also
specify the MIXERCONTROL_CONTROLF_UNIFORM flag.
cMultipleItems
Number of
items per channel that make up a MIXERCONTROL_CONTROLF_MULTIPLE control. This
number is always two or greater for multiple-item controls. If the control is
not a multiple-item control, do not use this member; it will be zero.
szShortName
Short string
that describes the audio line control specified by dwControlID. This
description should be appropriate to use as a concise label for the control.
szName
String that
describes the audio line control specified by dwControlID. This
description should be appropriate to use as a complete description for the
control.
Bounds
Union of
boundary types.
lMinimum
Minimum
signed value for a control that has a signed boundary nature. This member
cannot be used in conjunction with dwMinimun.
lMaximum
Maximum
signed value for a control that has a signed boundary nature. This member
cannot be used in conjunction with dwMaximun.
dwMinimum
Minimum
unsigned value for a control that has an unsigned boundary nature. This member
cannot be used in conjunction with lMinimun.
dwMaximum
Maximum
unsigned value for a control that has an unsigned boundary nature. This member
cannot be used in conjunction with lMaximum.
Metrics
Union of
boundary metrics.
cSteps
Number of
discrete ranges within the union specified for a control specified by the Bounds
member. This member overlaps with the other members of the Metrics
structure member and cannot be used in conjunction with those members.
cbCustomData
Size, in
bytes, required to contain the state of a custom control class. This member is
appropriate only for the MIXERCONTROL_CONTROLTYPE_CUSTOM control class.
To determine
if the dwMinimum, dwMaximum, lMinimum, lMaximum, cSteps,
and cbCustomData members are appropriate for a control class, see Control
Types.
The calling
application does not need to initialize any members of this structure because
the MIXERCONTROL structure is passed to the mixerGetLineControls function as a receiving
buffer that is referenced and described by the MIXERLINECONTROLS structure.
When mixerGetLineControls returns, the cbStruct member contains
the actual size of the information returned by the mixer device. The returned
information will not exceed the requested size, nor will it be smaller than the
MIXERCONTROL structure.
dwReserved
Reserved; do
not use.
See Also