mirror of
https://github.com/cookiengineer/audacity
synced 2025-10-26 07:13:49 +01:00
Remove some old erratta, and do a major tidy up of line endings and properties on source files
This commit is contained in:
ra
@@ -1,91 +1,91 @@
|
||||
<!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/4.77 [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>
|
||||
Writing a Callback Function</h2>
|
||||
|
||||
<blockquote>To write a program using PortAudio, you must include the "portaudio.h"
|
||||
include file. You may wish to read "<a href="portaudio_h.txt">portaudio.h</a>"
|
||||
because it contains a complete description of the PortAudio functions and
|
||||
constants.
|
||||
<blockquote>
|
||||
<pre>#include "portaudio.h"</pre>
|
||||
</blockquote>
|
||||
The next task is to write your custom callback function. It is a function
|
||||
that is called by the PortAudio engine whenever it has captured audio data,
|
||||
or when it needs more audio data for output.
|
||||
<p>Your callback function is often called by an interrupt, or low level
|
||||
process so you should not do any complex system activities like allocating
|
||||
memory, or reading or writing files, or printf(). Just crunch numbers and
|
||||
generate audio signals. What is safe or not safe will vary from platform
|
||||
to platform. On the Macintosh, for example, you can only call "interrupt
|
||||
safe" routines. Also do not call any PortAudio functions in the callback
|
||||
except for Pa_StreamTime() and Pa_GetCPULoad().
|
||||
<p>Your callback function must return an int and accept the exact parameters
|
||||
specified in this typedef:
|
||||
<blockquote>
|
||||
<pre>typedef int (PortAudioCallback)(
|
||||
void *inputBuffer, void *outputBuffer,
|
||||
unsigned long framesPerBuffer,
|
||||
PaTimestamp outTime, void *userData );</pre>
|
||||
</blockquote>
|
||||
Here is an example callback function from the test file "patests/patest_saw.c".
|
||||
It calculates a simple left and right sawtooth signal and writes it to
|
||||
the output buffer. Notice that in this example, the signals are of <tt>float</tt>
|
||||
data type. The signals must be between -1.0 and +1.0. You can also use
|
||||
16 bit integers or other formats which are specified during setup. You
|
||||
can pass a pointer to your data structure through PortAudio which will
|
||||
appear as <tt>userData</tt>.
|
||||
<blockquote>
|
||||
<pre>int patestCallback( void *inputBuffer, void *outputBuffer,
|
||||
unsigned long framesPerBuffer,
|
||||
PaTimestamp outTime, void *userData )
|
||||
{
|
||||
unsigned int i;
|
||||
/* Cast data passed through stream to our structure type. */
|
||||
paTestData *data = (paTestData*)userData;
|
||||
float *out = (float*)outputBuffer;
|
||||
|
||||
for( i=0; i<framesPerBuffer; i++ )
|
||||
{
|
||||
/* Stereo channels are interleaved. */
|
||||
*out++ = data->left_phase; /* left */
|
||||
*out++ = data->right_phase; /* right */
|
||||
|
||||
/* Generate simple sawtooth phaser that ranges between -1.0 and 1.0. */
|
||||
data->left_phase += 0.01f;
|
||||
/* When signal reaches top, drop back down. */
|
||||
if( data->left_phase >= 1.0f ) data->left_phase -= 2.0f;
|
||||
|
||||
/* higher pitch so we can distinguish left and right. */
|
||||
data->right_phase += 0.03f;
|
||||
if( data->right_phase >= 1.0f ) data->right_phase -= 2.0f;
|
||||
}
|
||||
return 0;
|
||||
}</pre>
|
||||
</blockquote>
|
||||
</blockquote>
|
||||
<font size=+2><a href="http://www.portaudio.com/">home</a> |
|
||||
<a href="pa_tutorial.html">contents</a>
|
||||
| <a href="pa_tut_over.html">previous</a> | <a href="pa_tut_init.html">next</a></font>
|
||||
</body>
|
||||
</html>
|
||||
<!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/4.77 [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>
|
||||
Writing a Callback Function</h2>
|
||||
|
||||
<blockquote>To write a program using PortAudio, you must include the "portaudio.h"
|
||||
include file. You may wish to read "<a href="portaudio_h.txt">portaudio.h</a>"
|
||||
because it contains a complete description of the PortAudio functions and
|
||||
constants.
|
||||
<blockquote>
|
||||
<pre>#include "portaudio.h"</pre>
|
||||
</blockquote>
|
||||
The next task is to write your custom callback function. It is a function
|
||||
that is called by the PortAudio engine whenever it has captured audio data,
|
||||
or when it needs more audio data for output.
|
||||
<p>Your callback function is often called by an interrupt, or low level
|
||||
process so you should not do any complex system activities like allocating
|
||||
memory, or reading or writing files, or printf(). Just crunch numbers and
|
||||
generate audio signals. What is safe or not safe will vary from platform
|
||||
to platform. On the Macintosh, for example, you can only call "interrupt
|
||||
safe" routines. Also do not call any PortAudio functions in the callback
|
||||
except for Pa_StreamTime() and Pa_GetCPULoad().
|
||||
<p>Your callback function must return an int and accept the exact parameters
|
||||
specified in this typedef:
|
||||
<blockquote>
|
||||
<pre>typedef int (PortAudioCallback)(
|
||||
void *inputBuffer, void *outputBuffer,
|
||||
unsigned long framesPerBuffer,
|
||||
PaTimestamp outTime, void *userData );</pre>
|
||||
</blockquote>
|
||||
Here is an example callback function from the test file "patests/patest_saw.c".
|
||||
It calculates a simple left and right sawtooth signal and writes it to
|
||||
the output buffer. Notice that in this example, the signals are of <tt>float</tt>
|
||||
data type. The signals must be between -1.0 and +1.0. You can also use
|
||||
16 bit integers or other formats which are specified during setup. You
|
||||
can pass a pointer to your data structure through PortAudio which will
|
||||
appear as <tt>userData</tt>.
|
||||
<blockquote>
|
||||
<pre>int patestCallback( void *inputBuffer, void *outputBuffer,
|
||||
unsigned long framesPerBuffer,
|
||||
PaTimestamp outTime, void *userData )
|
||||
{
|
||||
unsigned int i;
|
||||
/* Cast data passed through stream to our structure type. */
|
||||
paTestData *data = (paTestData*)userData;
|
||||
float *out = (float*)outputBuffer;
|
||||
|
||||
for( i=0; i<framesPerBuffer; i++ )
|
||||
{
|
||||
/* Stereo channels are interleaved. */
|
||||
*out++ = data->left_phase; /* left */
|
||||
*out++ = data->right_phase; /* right */
|
||||
|
||||
/* Generate simple sawtooth phaser that ranges between -1.0 and 1.0. */
|
||||
data->left_phase += 0.01f;
|
||||
/* When signal reaches top, drop back down. */
|
||||
if( data->left_phase >= 1.0f ) data->left_phase -= 2.0f;
|
||||
|
||||
/* higher pitch so we can distinguish left and right. */
|
||||
data->right_phase += 0.03f;
|
||||
if( data->right_phase >= 1.0f ) data->right_phase -= 2.0f;
|
||||
}
|
||||
return 0;
|
||||
}</pre>
|
||||
</blockquote>
|
||||
</blockquote>
|
||||
<font size=+2><a href="http://www.portaudio.com/">home</a> |
|
||||
<a href="pa_tutorial.html">contents</a>
|
||||
| <a href="pa_tut_over.html">previous</a> | <a href="pa_tut_init.html">next</a></font>
|
||||
</body>
|
||||
</html>
|
||||
|
||||
Reference in New Issue
Block a user