56 lines
2.3 KiB
HTML
56 lines
2.3 KiB
HTML
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<!doctype html public "-//w3c//dtd html 4.0 transitional//en">
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<html>
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
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<meta name="GENERATOR" content="Mozilla/4.75 [en]C-gatewaynet (Win98; U) [Netscape]">
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<meta name="Author" content="Phil Burk">
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<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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<meta name="KeyWords" content="audio, tutorial, library, portable, open-source, DirectSound,sound, music, JSyn, synthesis,">
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<title>PortAudio Tutorial</title>
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</head>
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<body>
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<center><table COLS=1 WIDTH="100%" BGCOLOR="#FADA7A" >
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<tr>
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<td>
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<center>
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<h1>
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PortAudio Tutorial</h1></center>
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</td>
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</tr>
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</table></center>
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<h2>
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Utility Functions</h2>
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<blockquote>Here are several more functions that are not critical, but
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may be handy when using PortAudio.
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<p>Pa_StreamActive() returns one when the stream in playing audio, zero
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when not playing, or a negative error number if the stream is invalid.
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The stream is active between calls to Pa_StartStream() and Pa_StopStream(),
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but may also become inactive if the callback returns a non-zero value.
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In the latter case, the stream is considered inactive after the last buffer
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has finished playing.
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<blockquote>
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<pre>PaError Pa_StreamActive( PortAudioStream *stream );</pre>
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</blockquote>
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Pa_StreamTime() returns the number of samples that have been generated.
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PaTimeStamp is a double precision number which is a convenient way to pass
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big numbers around even though we only need integers.
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<blockquote>
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<pre>PaTimestamp Pa_StreamTime( PortAudioStream *stream );</pre>
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</blockquote>
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The "CPU Load" is a fraction of total CPU time consumed by the stream's
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audio processing. A value of 0.5 would imply that PortAudio and the sound
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generating callback was consuming roughly 50% of the available CPU time.
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This function may be called from the callback function or the application.
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<blockquote>
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<pre>double Pa_GetCPULoad( PortAudioStream* stream );</pre>
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</blockquote>
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</blockquote>
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<font size=+2><a href="http://www.portaudio.com/">home</a> |
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<a href="pa_tutorial.html">contents</a> | <a href="pa_tut_term.html">previous</a>
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| <a href="pa_tut_devs.html">next</a></font>
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</body>
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</html>
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