User`s guide

From Wave Device
5-217
5From Wave Device
Purpose Read audio data from a standard audio device in real-time.
(Windows 95/98/NT only)
Library DSP Sources
Description The From Wave Device block reads audio data from a standard Windows audio
device in real-time. It is compatible with most popular Windows hardware,
including Sound Blaster cards. (Models that contain both this block and the To
Wave Device block require a duplex-capable sound card.)
The
Use default audio device parameter allows the block to detect and use the
system’s default audio hardware. This option should be selected on systems
that have a single sound device installed, or when the default sound device on
a multiple-device system is the desired source. In cases when the default sound
device is not the desired input source, deselect
Use default audio device, and
enter the desired device identification number in the
Audio device ID
parameter. The device ID is an integer value that the block associates with the
sound device. A three-device system, for example, has device ID numbers of
1, 2, and 3.
If the audio source contains two channels (stereo), the
Stereo check box should
be selected. If the audio source contains a single channel (mono), the
Stereo
check box should be deselected. For stereo input, the block’s output is an
M-by-2 matrix containing one frame (M consecutive samples) of audio data
from each of the two channels. For mono input, the block’s output is an M-by-1
matrix containing one frame (M consecutive samples) of audio data from the
mono input. The frame size, M, is specified by the
Samples per frame
parameter. For M=1, the output is sample-based; otherwise, the output is
frame-based.
The amplitude of the input from the sound device should be in the range ±1.
Values outside this range are clipped to the nearest allowable value. If the
audio signal is saturating at ±1, you can reduce the microphone gain from the
Multimedia Properties window (available through the Windows 95/98/NT
Control Panel). The audio data is processed in uncompressed PCM (pulse code
modulation) format, and should typically be sampled at one of the standard
Windows audio device rates: 8000, 11025, 22050, or 44100 Hz. You can select
one of these rates from the
Sample rate parameter. To specify a different rate,
select the
User-defined option and enter a value in the User-defined sample
rate
parameter.