MIXERCONTROLA structure (mmeapi.h)

The MIXERCONTROL structure describes the state and metrics of a single control for an audio line.

Syntax

typedef struct tagMIXERCONTROLA {
  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;
    } DUMMYSTRUCTNAME;
    struct {
      DWORD dwMinimum;
      DWORD dwMaximum;
    } DUMMYSTRUCTNAME2;
    DWORD dwReserved[6];
  } Bounds;
  union {
    DWORD cSteps;
    DWORD cbCustomData;
    DWORD dwReserved[6];
  } Metrics;
} MIXERCONTROLA, *PMIXERCONTROLA, *LPMIXERCONTROLA;

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:

Name	Descriptions
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:

Name	Description
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[MIXER_SHORT_NAME_CHARS]

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[MIXER_LONG_NAME_CHARS]

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.

Bounds.DUMMYSTRUCTNAME

Bounds.DUMMYSTRUCTNAME.lMinimum

Minimum signed value for a control that has a signed boundary nature. This member cannot be used in conjunction with dwMinimum.

Bounds.DUMMYSTRUCTNAME.lMaximum

Maximum signed value for a control that has a signed boundary nature. This member cannot be used in conjunction with dwMaximum.

Bounds.DUMMYSTRUCTNAME2

Bounds.DUMMYSTRUCTNAME2.dwMinimum

Minimum unsigned value for a control that has an unsigned boundary nature. This member cannot be used in conjunction with lMinimum.

Bounds.DUMMYSTRUCTNAME2.dwMaximum

Maximum unsigned value for a control that has an unsigned boundary nature. This member cannot be used in conjunction with lMaximum.

Bounds.dwReserved[6]

Reserved; do not use.

Metrics

Union of boundary metrics.

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.

Metrics.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.

Metrics.dwReserved[6]

Reserved; do not use.

Remarks

Note

The mmeapi.h header defines MIXERCONTROL as an alias that automatically selects the ANSI or Unicode version of this function based on the definition of the UNICODE preprocessor constant. Mixing usage of the encoding-neutral alias with code that is not encoding-neutral can lead to mismatches that result in compilation or runtime errors. For more information, see Conventions for Function Prototypes.

Requirements

Requirement	Value
Minimum supported client	Windows 2000 Professional [desktop apps only]
Minimum supported server	Windows 2000 Server [desktop apps only]
Header	mmeapi.h

See also

Audio Mixer Structures

Audio Mixers

MIXERLINECONTROLS

mixerGetLineControls