1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
|
<!doctype html public "-//w3c//dtd html 4.0 transitional//en">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<meta name="GENERATOR" content="Mozilla/4.75 [en]C-gatewaynet (Win98; U) [Netscape]">
<meta name="Author" content="Phil Burk">
<meta name="Description" content="Tutorial for PortAudio, a cross platform, open-source, audio I/O library.It provides a very simple API for recording and/or playing sound using a simple callback function.">
<meta name="KeyWords" content="audio, tutorial, library, portable, open-source, DirectSound,sound, music, JSyn, synthesis,">
<title>PortAudio Tutorial</title>
</head>
<body>
<center><table COLS=1 WIDTH="100%" BGCOLOR="#FADA7A" >
<tr>
<td>
<center>
<h1>
PortAudio Tutorial</h1></center>
</td>
</tr>
</table></center>
<h2>
Querying for Available Devices</h2>
<blockquote>There are often several different audio devices available in
a computer with different capabilities. They can differ in the sample rates
supported, bit widths, etc. PortAudio provides a simple way to query for
the available devices, and then pass the selected device to Pa_OpenStream().
For an example, see the file "pa_tests/pa_devs.c".
<p>To determine the number of devices:
<blockquote>
<pre>numDevices = Pa_CountDevices();</pre>
</blockquote>
You can then query each device in turn by calling Pa_GetDeviceInfo() with
an index.
<blockquote>
<pre>for( i=0; i<numDevices; i++ ) {
pdi = Pa_GetDeviceInfo( i );</pre>
</blockquote>
It will return a pointer to a <tt>PaDeviceInfo</tt> structure which is
defined as:
<blockquote>
<pre>typedef struct{
int structVersion;
const char *name;
int maxInputChannels;
int maxOutputChannels;
/* Number of discrete rates, or -1 if range supported. */
int numSampleRates;
/* Array of supported sample rates, or {min,max} if range supported. */
const double *sampleRates;
PaSampleFormat nativeSampleFormat;
}PaDeviceInfo;</pre>
</blockquote>
If the device supports a continuous range of sample rates, then numSampleRates
will equal -1, and the sampleRates array will have two values, the minimum
and maximum rate.
<p>The device information is allocated by Pa_Initialize() and freed by
Pa_Terminate() so you do not have to free() the structure returned by Pa_GetDeviceInfo().</blockquote>
<font size=+2><a href="http://www.portaudio.com/">home</a> |
<a href="pa_tutorial.html">contents</a>
| <a href="pa_tut_util.html">previous</a> | <a href="pa_tut_rw.html">next</a></font>
</body>
</html>
|
