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