MCI_SETAUDIO
The MCI_SETAUDIO
command sets values associated with audio playback and capture. Digital-video
and VCR devices recognize this command.
MCIERROR mciSendCommand(MCIDEVICEID wDeviceID,
MCI_SETAUDIO,
DWORD dwFlags, (DWORD)
(LPMCI_GENERIC_PARMS) lpSetAudio);
Parameters
wDeviceID
Device
identifier of the MCI device that is to receive the command message.
dwFlags
MCI_NOTIFY,
MCI_WAIT, or MCI_TEST. For information about these flags, see The Wait,
Notify, and Test Flags.
lpSetAudio
Address of an
MCI_GENERIC_PARMS
structure. (Devices with extended command sets might replace this structure
with a device-specific structure.)
Return Values
Returns zero
if successful or an error otherwise.
Remarks
The following
flags apply to the digitalvideo device type:
MCI_DGV_SETAUDIO_ALG
The lpstrAlgorithm
member of the structure identified by lpSetAudio contains an address of
a buffer containing the name of an audio compression algorithm. The compression
algorithm is used by subsequent MCI_RESERVE or MCI_RECORDBEWKAT commands. The available algorithms are
device dependent. If the algorithm is incompatible with the current file
format, the file format is changed to the default format for the algorithm.
MCI_DGV_SETAUDIO_CLOCKTIME
The time
specified is in milliseconds and is absolute time when used with
MCI_DGV_SETAUDIO_OVER. (This time is not in step with the playing of the
workspace.)
MCI_DGV_SETAUDIO_INPUT
Modifies the
bass, treble, or volume flag so that it affects the input signal and modifies
what is recorded. If possible, this is the default when monitoring the input.
MCI_DGV_SETAUDIO_ITEM
An audio
constant is specified in the dwItem member of the structure identified
by lpSetAudio. The constant identifies the value that is being set. The
following constants are defined:
MCI_DGV_SETAUDIO_AVGBYTESPERSEC
The average
number of bytes is specified in the dwValue member of the structure
identified by lpSetAudio. This value sets the average number of bytes
per second for playing or recording in the PCM (Pulse Code Modulation) and
ADPCM (Adaptive Differential Pulse Code Modulation) formats. The file is saved
in this format.
MCI_DGV_SETAUDIO_BASS
The audio low
frequency level is specified as a factor in the dwValue member of the
structure identified by lpSetAudio.
MCI_DGV_SETAUDIO_BITSPERSAMPLE
The number of
bits per sample is specified in the dwValue member of the structure
identified by lpSetAudio. This value sets the number of bits per sample
played or recorded in the PCM format. The file is saved in this format.
MCI_DGV_SETAUDIO_BLOCKALIGN
The data
block alignment is specified in the dwValue member of the structure
identified by lpSetAudio. This value sets the alignment of data blocks
relative to the start of input waveform data.
MCI_DGV_SETAUDIO_SAMPLESPERSEC
The sample
rate is specified in the dwValue member of the structure identified by lpSetAudio.
This value sets the sample rate for playing and recording with the PCM and
ADPCM algorithms. The file is saved in this format.
MCI_DGV_SETAUDIO_SOURCE
A constant
specifying the source of audio input is included in the dwValue member
of the structure identified by lpSetAudio. The following constants are
defined for the audio input sources:
MCI_DGV_SETAUDIO_SOURCE_AVERAGE
The average of the left and right audio
channels.
MCI_DGV_SETAUDIO_SOURCE_LEFT
Left audio channel.
MCI_DGV_SETAUDIO_SOURCE_RIGHT
Right audio channel.
MCI_DGV_SETAUDIO_SOURCE_STEREO
Stereo.
MCI_DGV_SETAUDIO_STREAM
An
audio-stream is specified in the dwValue member of the structure
identified by lpSetAudio. The integer value specifies the audio stream
played back from the workspace. If the stream is not specified, the first
physically interleaved audio stream is played.
MCI_DGV_SETAUDIO_TREBLE
The audio
high-frequency level is specified as a factor in the dwValue member of
the structure identified by lpSetAudio.
MCI_DGV_SETAUDIO_VOLUME
The audio
level for one or both audio channels is specified as a factor in the dwValue
member of the structure identified by lpSetAudio. If the left and right
volumes have been set to different values, then the ratio of left to right
volume is approximately unchanged.
MCI_DGV_SETAUDIO_LEFT
Enables the
left audio channel when used with MCI_SET_ON. Disables the left audio channel
when used with MCI_SET_OFF. When this flag is used with the combination of
MCI_DGV_SETAUDIO_VALUE and MCI_DGV_SETAUDIO_VOLUME, it sets the volume of the
left audio channel. When this flag is used with MCI_DGV_SETAUDIO_SOURCE, it
specifies the left audio channel as the source for the audio input digitizer.
MCI_DGV_SETAUDIO_OVER
A transition
length parameter is included in the dwOver member of the structure
identified by lpSetAudio. The length value specifies how long (in units
of the current time format) it should take to make a change that uses a factor.
If this flag is not used, changes occur immediately.
MCI_DGV_SETAUDIO_QUALITY
The lpstrQuality
member of the structure identified by lpSetAudio contains an address of
a buffer defining the audio quality. A text-string within the buffer specifies
the characteristics of the audio compression algorithm.
The
MCI_DGV_SETAUDIO_ALG flag can be used to select a quality descriptor for the
specified algorithm. If this flag is omitted, then the current algorithm is
used.
The
algorithms and descriptor names available depend on the device. Each device
supplies documentation for the available algorithms and a description of the
applicable descriptor names. The MCI_QUALITYVDIDKL command can define additional descriptor
names.
MCI_DGV_SETAUDIO_RECORD
Specifies
whether recording includes or excludes audio data. When combined with
MCI_SET_ON, audio data is recorded. When combined with MCI_SET_OFF, audio data
is excluded. The default includes audio data.
MCI_DGV_SETAUDIO_RIGHT
Enables the
right audio channel when used with MCI_SET_ON. Disables the right audio channel
when used with MCI_SET_OFF. When this flag is used with the combination of
MCI_DGV_SETAUDIO_VALUE and MCI_DGV_SETAUDIO_VOLUME, it sets the volume of the
right audio channel.
MCI_DGV_SETAUDIO_VALUE
A value is
specified in the dwValue member of the structure identified by lpSetAudio.
The meaning of the value is specified by the constant defined for the
MCI_DGV_SETAUDIO_ITEM flag.
MCI_SET_OFF
Disables the
specified audio channel.
MCI_SET_ON
Enables the
specified audio channel.
MCI_SETAUDIO_OUTPUT
Modifies the
bass, treble, or volume flag so that it modifies only the played signal and not
what is recorded. If possible, this is the default when monitoring the input.
For
digital-video devices, the lpSetAudio parameter points to an MCI_DGV_SETAUDIO_PARMS structure.
The following
additional flags are used with the vcr device type:
MCI_VCR_SETAUDIO_RECORD
Sets the
audio recording to on or off, which is used in conjunction with one of
following flags:
MCI_SET_ON
Audio
recording on.
MCI_SET_OFF
Audio
recording off. It might be necessary to first turn off the assemble recording
(using the MCI_SET
command with the MCI_VCR_SET_ASSEMBLE_RECORD flag set to off) before the
audio recording can be turned off.
MCI_TRACK
The
dwTrack member of the structure identified by lpSetAudio
specifies which track is affected by the command.
MCI_VCR_SETAUDIO_SOURCE
Sets the
audio source. This flag must be used with the MCI_VCR_SETAUDIO_TO flag.
MCI_VCR_SETAUDIO_MONITOR
Sets the
audio source monitor. This flag must be used with the MCI_VCR_SETAUDIO_TO flag.
MCI_VCR_SETAUDIO_TO
The dwTo member
of the structure identified by lpSetAudio contains a constant describing
the type of input or monitored input. It must be one of the following:
MCI_VCR_SRC_TYPE_TUNER
Type is
tuner.
MCI_VCR_SRC_TYPE_LINE
Type is line.
MCI_VCR_SRC_TYPE_AUX
Type is
auxiliary.
MCI_VCR_SRC_TYPE_GENERIC
Type is
generic.
MCI_VCR_SRC_TYPE_MUTE
Type is mute.
This can be used only with the MCI_VCR_SETAUDIO_SOURCE flag.
MCI_VCR_SRC_TYPE_OUTPUT
Type is
output.
MCI_VCR_SETAUDIO_NUMBER
The
dwNumber member of the structure identified by lpSetAudio contains the
audio input (of the type specified in the dwTo member) to use.
For VCR
devices, the lpSetAudio parameter points to an MCI_VCR_SETAUDIO_PARMS structure.
See Also