From ae6b5d89ea93b95c2990895077cf5e8f0bba9ad9 Mon Sep 17 00:00:00 2001 From: Guenter Geiger Date: Mon, 2 Feb 2004 11:28:02 +0000 Subject: This commit was generated by cvs2svn to compensate for changes in r1301, which included commits to RCS files with non-trunk default branches. svn path=/trunk/; revision=1302 --- pd/portaudio_v18/docs/pa_tut_rw.html | 79 ++++++++++++++++++++++++++++++++++++ 1 file changed, 79 insertions(+) create mode 100644 pd/portaudio_v18/docs/pa_tut_rw.html (limited to 'pd/portaudio_v18/docs/pa_tut_rw.html') diff --git a/pd/portaudio_v18/docs/pa_tut_rw.html b/pd/portaudio_v18/docs/pa_tut_rw.html new file mode 100644 index 00000000..93c7b8bb --- /dev/null +++ b/pd/portaudio_v18/docs/pa_tut_rw.html @@ -0,0 +1,79 @@ + + + + + + + + + PortAudio Tutorial + + +  +
+ + + +
+
+

+PortAudio Tutorial

+
+ +

+Blocking Read/Write Functions

+ +
[Note: These functions are not part of the official PortAudio +API. They are simply built on top of PortAudio as an extra utility. Also +note that they are under evaluation and their definition may change.] +

There are two fundamentally different ways to design an audio API. One +is to use callback functions the way we have already shown. The callback +function operates under an interrupt or background thread This leaves the +foreground application free to do other things while the audio just runs +in the background. But this can sometimes be awkward. +

So we have provided an alternative technique that lets a program generate +audio in the foreground and then just write it to the audio stream as if +it was a file. If there is not enough room in the audio buffer for more +data, then the write function will just block until more room is available. +This can make it very easy to write an audio example. To use this tool, +you must add the files "pablio/pablio.c" and "pablio/ringbuffer.c" to your +project. You must also: +

+
#include "pablio.h"
+
+Here is a short excerpt of a program that opens a stream for input and +output. It then reads a block of samples from input, and writes them to +output, in a loop.  The complete example can be found in "pablio/test_rw.c". +
+
    #define SAMPLES_PER_FRAME     (2)
+    #define FRAMES_PER_BLOCK    (1024)
+    SAMPLE          samples[SAMPLES_PER_FRAME * FRAMES_PER_BLOCK];
+    PaError         err;
+    PABLIO_Stream  *aStream;
+
+/* Open simplified blocking I/O layer on top of PortAudio. */
+    err = OpenAudioStream( &rwbl, SAMPLE_RATE, paFloat32,
+                         (PABLIO_READ_WRITE | PABLIO_STEREO) );
+    if( err != paNoError ) goto error;
+
+/* Process samples in the foreground. */
+    for( i=0; i<(NUM_SECONDS * SAMPLE_RATE); i++ )
+    {
+    /* Read one block of data into sample array from audio input. */
+        ReadAudioStream( aStream, samples, FRAMES_PER_BLOCK );
+    /*
+    ** At this point you could process the data in samples array,
+    ** and write the result back to the same samples array.
+    */
+    /* Write that same frame of data to output. */
+        WriteAudioStream( aStream, samples, FRAMES_PER_BLOCK );
+    }
+
+    CloseAudioStream( aStream );
+
+
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