From 2e416ee0095f1bf608f849f156d564e0f45fb8ab Mon Sep 17 00:00:00 2001 From: Guenter Geiger Date: Mon, 2 Feb 2004 12:18:59 +0000 Subject: merged in version_0_37_1test6 svn path=/trunk/; revision=1305 --- pd/portaudio/docs/pa_tut_callback.html | 91 ---------------------------------- 1 file changed, 91 deletions(-) delete mode 100644 pd/portaudio/docs/pa_tut_callback.html (limited to 'pd/portaudio/docs/pa_tut_callback.html') diff --git a/pd/portaudio/docs/pa_tut_callback.html b/pd/portaudio/docs/pa_tut_callback.html deleted file mode 100644 index f5ccaf0f..00000000 --- a/pd/portaudio/docs/pa_tut_callback.html +++ /dev/null @@ -1,91 +0,0 @@ - - - - - - - - - PortAudio Tutorial - - -  -
- - - -
-
-

-PortAudio Tutorial

-
- -

-Writing a Callback Function

- -
To write a program using PortAudio, you must include the "portaudio.h" -include file. You may wish to read "portaudio.h" -because it contains a complete description of the PortAudio functions and -constants. -
-
#include "portaudio.h"
-
-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. -

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(). -

Your callback function must return an int and accept the exact parameters -specified in this typedef: -

-
typedef int (PortAudioCallback)(
-               void *inputBuffer, void *outputBuffer,
-               unsigned long framesPerBuffer,
-               PaTimestamp outTime, void *userData );
-
-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 float -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 userData. -
-
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;
-}
-
-
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