1 /*
2 * $Id: pa_minlat.c,v 1.1 2006/04/30 16:23:59 jcr13 Exp $
3 * paminlat.c
4 * Experiment with different numbers of buffers to determine the
5 * minimum latency for a computer.
6 *
7 * Author: Phil Burk http://www.softsynth.com
8 *
9 * This program uses the PortAudio Portable Audio Library.
10 * For more information see: http://www.portaudio.com
11 * Copyright (c) 1999-2000 Ross Bencina and Phil Burk
12 *
13 * Permission is hereby granted, free of charge, to any person obtaining
14 * a copy of this software and associated documentation files
15 * (the "Software"), to deal in the Software without restriction,
16 * including without limitation the rights to use, copy, modify, merge,
17 * publish, distribute, sublicense, and/or sell copies of the Software,
18 * and to permit persons to whom the Software is furnished to do so,
19 * subject to the following conditions:
20 *
21 * The above copyright notice and this permission notice shall be
22 * included in all copies or substantial portions of the Software.
23 *
24 * Any person wishing to distribute modifications to the Software is
25 * requested to send the modifications to the original developer so that
26 * they can be incorporated into the canonical version.
27 *
28 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
29 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
30 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
31 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR
32 * ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF
33 * CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
34 * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
35 *
36 */
37 #include <stdio.h>
38 #include <stdlib.h>
39 #include <math.h>
40 #include "portaudio.h"
41
42 #ifndef M_PI
43 #define M_PI (3.14159265)
44 #endif
45 #define TWOPI (M_PI * 2.0)
46
47 #define DEFAULT_BUFFER_SIZE (64)
48
49 typedef struct
50 {
51 double left_phase;
52 double right_phase;
53 }
54 paTestData;
55
56 /* Very simple synthesis routine to generate two sine waves. */
paminlatCallback(void * inputBuffer,void * outputBuffer,unsigned long framesPerBuffer,PaTimestamp outTime,void * userData)57 static int paminlatCallback( void *inputBuffer, void *outputBuffer,
58 unsigned long framesPerBuffer,
59 PaTimestamp outTime, void *userData )
60 {
61 paTestData *data = (paTestData*)userData;
62 float *out = (float*)outputBuffer;
63 unsigned int i;
64 double left_phaseInc = 0.02;
65 double right_phaseInc = 0.06;
66
67 double left_phase = data->left_phase;
68 double right_phase = data->right_phase;
69
70 for( i=0; i<framesPerBuffer; i++ )
71 {
72 left_phase += left_phaseInc;
73 if( left_phase > TWOPI ) left_phase -= TWOPI;
74 *out++ = (float) sin( left_phase );
75
76 right_phase += right_phaseInc;
77 if( right_phase > TWOPI ) right_phase -= TWOPI;
78 *out++ = (float) sin( right_phase );
79 }
80
81 data->left_phase = left_phase;
82 data->right_phase = right_phase;
83 return 0;
84 }
85 void main( int argc, char **argv );
main(int argc,char ** argv)86 void main( int argc, char **argv )
87 {
88 PortAudioStream *stream;
89 PaError err;
90 paTestData data;
91 int go;
92 int numBuffers = 0;
93 int minBuffers = 0;
94 int framesPerBuffer;
95 double sampleRate = 44100.0;
96 char str[256];
97 printf("paminlat - Determine minimum latency for your computer.\n");
98 printf(" usage: paminlat {framesPerBuffer}\n");
99 printf(" for example: paminlat 256\n");
100 printf("Adjust your stereo until you hear a smooth tone in each speaker.\n");
101 printf("Then try to find the smallest number of buffers that still sounds smooth.\n");
102 printf("Note that the sound will stop momentarily when you change the number of buffers.\n");
103 /* Get bufferSize from command line. */
104 framesPerBuffer = ( argc > 1 ) ? atol( argv[1] ) : DEFAULT_BUFFER_SIZE;
105 printf("Frames per buffer = %d\n", framesPerBuffer );
106
107 data.left_phase = data.right_phase = 0.0;
108 err = Pa_Initialize();
109 if( err != paNoError ) goto error;
110 /* Ask PortAudio for the recommended minimum number of buffers. */
111 numBuffers = minBuffers = Pa_GetMinNumBuffers( framesPerBuffer, sampleRate );
112 printf("NumBuffers set to %d based on a call to Pa_GetMinNumBuffers()\n", numBuffers );
113 /* Try different numBuffers in a loop. */
114 go = 1;
115 while( go )
116 {
117
118 printf("Latency = framesPerBuffer * numBuffers = %d * %d = %d frames = %d msecs.\n",
119 framesPerBuffer, numBuffers, framesPerBuffer*numBuffers,
120 (int)((1000 * framesPerBuffer * numBuffers) / sampleRate) );
121 err = Pa_OpenStream(
122 &stream,
123 paNoDevice,
124 0, /* no input */
125 paFloat32, /* 32 bit floating point input */
126 NULL,
127 Pa_GetDefaultOutputDeviceID(), /* default output device */
128 2, /* stereo output */
129 paFloat32, /* 32 bit floating point output */
130 NULL,
131 sampleRate,
132 framesPerBuffer,
133 numBuffers, /* number of buffers */
134 paClipOff, /* we won't output out of range samples so don't bother clipping them */
135 paminlatCallback,
136 &data );
137 if( err != paNoError ) goto error;
138 if( stream == NULL ) goto error;
139 /* Start audio. */
140 err = Pa_StartStream( stream );
141 if( err != paNoError ) goto error;
142 /* Ask user for a new number of buffers. */
143 printf("\nMove windows around to see if the sound glitches.\n");
144 printf("NumBuffers currently %d, enter new number, or 'q' to quit: ", numBuffers );
145 gets( str );
146 if( str[0] == 'q' ) go = 0;
147 else
148 {
149 numBuffers = atol( str );
150 if( numBuffers < minBuffers )
151 {
152 printf( "numBuffers below minimum of %d! Set to minimum!!!\n", minBuffers );
153 numBuffers = minBuffers;
154 }
155 }
156 /* Stop sound until ENTER hit. */
157 err = Pa_StopStream( stream );
158 if( err != paNoError ) goto error;
159 err = Pa_CloseStream( stream );
160 if( err != paNoError ) goto error;
161 }
162 printf("A good setting for latency would be somewhat higher than\n");
163 printf("the minimum latency that worked.\n");
164 printf("PortAudio: Test finished.\n");
165 Pa_Terminate();
166 return;
167 error:
168 Pa_Terminate();
169 fprintf( stderr, "An error occured while using the portaudio stream\n" );
170 fprintf( stderr, "Error number: %d\n", err );
171 fprintf( stderr, "Error message: %s\n", Pa_GetErrorText( err ) );
172 }
173