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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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<title>PortAudio Tutorial</title>
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<h1>
PortAudio Tutorial</h1></center>
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<h2>
Utility Functions</h2>
<blockquote>Here are several more functions that are not critical, but
may be handy when using PortAudio.
<p>Pa_StreamActive() returns one when the stream in playing audio, zero
when not playing, or a negative error number if the stream is invalid.
The stream is active between calls to Pa_StartStream() and Pa_StopStream(),
but may also become inactive if the callback returns a non-zero value.
In the latter case, the stream is considered inactive after the last buffer
has finished playing.
<blockquote>
<pre>PaError Pa_StreamActive( PortAudioStream *stream );</pre>
</blockquote>
Pa_StreamTime() returns the number of samples that have been generated.
PaTimeStamp is a double precision number which is a convenient way to pass
big numbers around even though we only need integers.
<blockquote>
<pre>PaTimestamp Pa_StreamTime( PortAudioStream *stream );</pre>
</blockquote>
The "CPU Load" is a fraction of total CPU time consumed by the stream's
audio processing. A value of 0.5 would imply that PortAudio and the sound
generating callback was consuming roughly 50% of the available CPU time.
This function may be called from the callback function or the application.
<blockquote>
<pre>double Pa_GetCPULoad( PortAudioStream* stream );</pre>
</blockquote>
</blockquote>
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