From baefbbdc4a79daeefbb9c5dcb24c96baf4300167 Mon Sep 17 00:00:00 2001
From: philburk <philburk@0f58301d-fd10-0410-b4af-bbb618454e57>
Date: Fri, 19 Apr 2002 18:31:13 +0000
Subject: [PATCH] Change sine generation method so that sine waves don't line
 up with PA buffers. This was causing it to appear that audio was OK even when
 buffers were dropped..

---
 pa_tests/pa_minlat.c | 40 ++++++++++++++++++++++++----------------
 1 file changed, 24 insertions(+), 16 deletions(-)

diff --git a/pa_tests/pa_minlat.c b/pa_tests/pa_minlat.c
index bc9f185..533b8c4 100644
--- a/pa_tests/pa_minlat.c
+++ b/pa_tests/pa_minlat.c
@@ -38,18 +38,21 @@
 #include <stdlib.h>
 #include <math.h>
 #include "portaudio.h"
+
 #ifndef M_PI
 #define M_PI  (3.14159265)
 #endif
+#define TWOPI (M_PI * 2.0)
+
 #define DEFAULT_BUFFER_SIZE   (64)
 #define TABLE_SIZE   (200)
 typedef struct
 {
-    float sine[TABLE_SIZE];
-    int left_phase;
-    int right_phase;
+    double left_phase;
+    double right_phase;
 }
 paTestData;
+
 /* Very simple synthesis routine to generate two sine waves. */
 static int paminlatCallback( void *inputBuffer, void *outputBuffer,
                              unsigned long framesPerBuffer,
@@ -58,15 +61,25 @@ static int paminlatCallback( void *inputBuffer, void *outputBuffer,
     paTestData *data = (paTestData*)userData;
     float *out = (float*)outputBuffer;
     unsigned int i;
+    double left_phaseInc = 0.02;
+    double right_phaseInc = 0.06;
+
+    double left_phase = data->left_phase;
+    double right_phase = data->right_phase;
+
     for( i=0; i<framesPerBuffer; i++ )
     {
-        *out++ = data->sine[data->left_phase];  /* left */
-        *out++ = data->sine[data->right_phase];  /* right */
-        data->left_phase += 1;
-        if( data->left_phase >= TABLE_SIZE ) data->left_phase -= TABLE_SIZE;
-        data->right_phase += 3; /* higher pitch so we can distinguish left and right. */
-        if( data->right_phase >= TABLE_SIZE ) data->right_phase -= TABLE_SIZE;
+        left_phase += left_phaseInc;
+        if( left_phase > TWOPI ) left_phase -= TWOPI;
+        *out++ = (float) sin( left_phase );
+
+        right_phase += right_phaseInc;
+        if( right_phase > TWOPI ) right_phase -= TWOPI;
+        *out++ = (float) sin( right_phase );
     }
+
+    data->left_phase = left_phase;
+    data->right_phase = right_phase;
     return 0;
 }
 void main( int argc, char **argv );
@@ -75,7 +88,6 @@ void main( int argc, char **argv )
     PortAudioStream *stream;
     PaError err;
     paTestData data;
-    int    i;
     int    go;
     int    numBuffers = 0;
     int    minBuffers = 0;
@@ -91,12 +103,8 @@ void main( int argc, char **argv )
     /* Get bufferSize from command line. */
     framesPerBuffer = ( argc > 1 ) ? atol( argv[1] ) : DEFAULT_BUFFER_SIZE;
     printf("Frames per buffer = %d\n", framesPerBuffer );
-    /* Initialise sinusoidal wavetable. */
-    for( i=0; i<TABLE_SIZE; i++ )
-    {
-        data.sine[i] = (float) sin( ((double)i/(double)TABLE_SIZE) * M_PI * 2. );
-    }
-    data.left_phase = data.right_phase = 0;
+
+    data.left_phase = data.right_phase = 0.0;
     err = Pa_Initialize();
     if( err != paNoError ) goto error;
     /* Ask PortAudio for the recommended minimum number of buffers. */
-- 
2.43.0