blob: 52ba57092646fca2fb56090562d9b9e761878582 (
plain)
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
66
67
68
69
70
71
72
|
<HTML>
<HEAD>
<TITLE>The RtAudio Home Page</TITLE>
<LINK HREF="doxygen.css" REL="stylesheet" TYPE="text/css">
<LINK REL="SHORTCUT ICON" HREF="http://www.music.mcgill.ca/~gary/favicon.ico">
</HEAD>
<BODY BGCOLOR="#FFFFFF">
<CENTER>
<a class="qindex" href="index.html">Home</a> <a class="qindex" href="annotated.html">Class/Enum List</a> <a class="qindex" href="files.html">File List</a> <a class="qindex" href="functions.html">Compound Members</a> </CENTER>
<HR>
<!-- Generated by Doxygen 1.4.4 -->
<h1><a class="anchor" name="probe">Probing Device Capabilities</a></h1>A programmer may wish to query the available audio device capabilities before deciding which to use. The following example outlines how this can be done.<p>
<div class="fragment"><pre class="fragment"><span class="comment">// audioprobe.cpp</span>
<span class="preprocessor">#include <iostream></span>
<span class="preprocessor">#include "<a class="code" href="RtAudio_8h.html">RtAudio.h</a>"</span>
<span class="keywordtype">int</span> main()
{
<a class="code" href="classRtAudio.html">RtAudio</a> audio;
<span class="comment">// Determine the number of devices available</span>
<span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> devices = audio.<a class="code" href="classRtAudio.html#a3">getDeviceCount</a>();
<span class="comment">// Scan through devices for various capabilities</span>
<a class="code" href="structRtAudio_1_1DeviceInfo.html">RtAudio::DeviceInfo</a> info;
<span class="keywordflow">for</span> ( <span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> i=1; i<=devices; i++ ) {
info = audio.<a class="code" href="classRtAudio.html#a4">getDeviceInfo</a>( i );
<span class="keywordflow">if</span> ( info.<a class="code" href="structRtAudio_1_1DeviceInfo.html#o0">probed</a> == <span class="keyword">true</span> ) {
<span class="comment">// Print, for example, the maximum number of output channels for each device</span>
std::cout << <span class="stringliteral">"device = "</span> << i;
std::cout << <span class="stringliteral">": maximum output channels = "</span> << info.<a class="code" href="structRtAudio_1_1DeviceInfo.html#o2">outputChannels</a> << <span class="stringliteral">"\n"</span>;
}
}
<span class="keywordflow">return</span> 0;
}
</pre></div><p>
The <a class="el" href="structRtAudio_1_1DeviceInfo.html">RtAudio::DeviceInfo</a> structure is defined in <a class="el" href="RtAudio_8h.html">RtAudio.h</a> and provides a variety of information useful in assessing the capabilities of a device:<p>
<div class="fragment"><pre class="fragment"> <span class="keyword">typedef</span> <span class="keyword">struct </span><a class="code" href="structRtAudio_1_1DeviceInfo.html">RtAudio::DeviceInfo</a> {
<span class="keywordtype">bool</span> probed; <span class="comment">// true if the device capabilities were successfully probed.</span>
std::string name; <span class="comment">// Character string device identifier.</span>
<span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> outputChannels; <span class="comment">// Maximum output channels supported by device.</span>
<span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> inputChannels; <span class="comment">// Maximum input channels supported by device.</span>
<span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> duplexChannels; <span class="comment">// Maximum simultaneous input/output channels supported by device.</span>
<span class="keywordtype">bool</span> isDefaultOutput; <span class="comment">// true if this is the default output device.</span>
<span class="keywordtype">bool</span> isDefaultInput; <span class="comment">// true if this is the default input device.</span>
std::vector<unsigned int> sampleRates; <span class="comment">// Supported sample rates.</span>
<a class="code" href="RtAudio_8h.html#a1">RtAudioFormat</a> nativeFormats; <span class="comment">// Bit mask of supported data formats.</span>
};
</pre></div><p>
The following data formats are defined and fully supported by <a class="el" href="classRtAudio.html">RtAudio</a>:<p>
<div class="fragment"><pre class="fragment"> <span class="keyword">typedef</span> <span class="keywordtype">unsigned</span> <span class="keywordtype">long</span> <a class="code" href="RtAudio_8h.html#a1">RtAudioFormat</a>;
<span class="keyword">static</span> <span class="keyword">const</span> RtAudioFormat RTAUDIO_SINT8; <span class="comment">// Signed 8-bit integer</span>
<span class="keyword">static</span> <span class="keyword">const</span> RtAudioFormat RTAUDIO_SINT16; <span class="comment">// Signed 16-bit integer</span>
<span class="keyword">static</span> <span class="keyword">const</span> RtAudioFormat RTAUDIO_SINT24; <span class="comment">// Signed 24-bit integer (lower 3 bytes of 32-bit signed integer.)</span>
<span class="keyword">static</span> <span class="keyword">const</span> RtAudioFormat RTAUDIO_SINT32; <span class="comment">// Signed 32-bit integer</span>
<span class="keyword">static</span> <span class="keyword">const</span> RtAudioFormat RTAUDIO_FLOAT32; <span class="comment">// 32-bit float normalized between +/- 1.0</span>
<span class="keyword">static</span> <span class="keyword">const</span> RtAudioFormat RTAUDIO_FLOAT64; <span class="comment">// 64-bit double normalized between +/- 1.0</span>
</pre></div><p>
The <code>nativeFormats</code> member of the <a class="el" href="structRtAudio_1_1DeviceInfo.html">RtAudio::DeviceInfo</a> structure is a bit mask of the above formats which are natively supported by the device. However, <a class="el" href="classRtAudio.html">RtAudio</a> will automatically provide format conversion if a particular format is not natively supported. When the <code>probed</code> member of the <a class="el" href="structRtAudio_1_1DeviceInfo.html">RtAudio::DeviceInfo</a> structure is false, the remaining structure members are undefined and the device is probably unusable.<p>
Some audio devices may require a minimum channel value greater than one. <a class="el" href="classRtAudio.html">RtAudio</a> will provide automatic channel number compensation when the number of channels set by the user is less than that required by the device. Channel compensation is <em>NOT</em> possible when the number of channels set by the user is greater than that supported by the device.<p>
It should be noted that the capabilities reported by a device driver or underlying audio API are not always accurate and/or may be dependent on a combination of device settings. For this reason, <a class="el" href="classRtAudio.html">RtAudio</a> does not rely on the queried values when attempting to open a stream. <HR>
<table><tr><td><img src="../images/mcgill.gif" width=165></td>
<td>©2001-2008 Gary P. Scavone, McGill University. All Rights Reserved.<br>Maintained by <a href="http://www.music.mcgill.ca/~gary/">Gary P. Scavone</a>.</td></tr>
</table>
</BODY>
</HTML>
|
