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comparison src/audio/dummy/SDL_dummyaudio.c @ 1537:60620d71e324

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Corrected dummy audio callback firing to be realistic, cleaned up tabs.
author Ryan C. Gordon <icculus@icculus.org>
date Tue, 14 Mar 2006 19:12:49 +0000
parents 38c1eb6b0083
children b1f8c14f0df5
comparison
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1536:5151662ab728 1537:60620d71e324
17 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA 17 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
18 18
19 Sam Lantinga 19 Sam Lantinga
20 slouken@libsdl.org 20 slouken@libsdl.org
21 21
22 This file hacked^H^H^H^H^H^Hwritten by Ryan C. Gordon 22 This file written by Ryan C. Gordon (icculus@icculus.org)
23 (icculus@icculus.org)
24 */ 23 */
25 #include "SDL_config.h" 24 #include "SDL_config.h"
26 25
27 /* Output audio to nowhere... */ 26 /* Output audio to nowhere... */
28 27
34 #include "../SDL_audiodev_c.h" 33 #include "../SDL_audiodev_c.h"
35 #include "SDL_dummyaudio.h" 34 #include "SDL_dummyaudio.h"
36 35
37 /* The tag name used by DUMMY audio */ 36 /* The tag name used by DUMMY audio */
38 #define DUMMYAUD_DRIVER_NAME "dummy" 37 #define DUMMYAUD_DRIVER_NAME "dummy"
39
40 /* environment variables and defaults. */
41 #define DUMMYENVR_WRITEDELAY "SDL_DUMMYAUDIODELAY"
42 #define DUMMYDEFAULT_WRITEDELAY 150
43 38
44 /* Audio driver functions */ 39 /* Audio driver functions */
45 static int DUMMYAUD_OpenAudio(_THIS, SDL_AudioSpec *spec); 40 static int DUMMYAUD_OpenAudio(_THIS, SDL_AudioSpec *spec);
46 static void DUMMYAUD_WaitAudio(_THIS); 41 static void DUMMYAUD_WaitAudio(_THIS);
47 static void DUMMYAUD_PlayAudio(_THIS); 42 static void DUMMYAUD_PlayAudio(_THIS);
83 } 78 }
84 return(0); 79 return(0);
85 } 80 }
86 SDL_memset(this->hidden, 0, (sizeof *this->hidden)); 81 SDL_memset(this->hidden, 0, (sizeof *this->hidden));
87 82
88 envr = SDL_getenv(DUMMYENVR_WRITEDELAY);
89 this->hidden->write_delay = (envr) ? SDL_atoi(envr) : DUMMYDEFAULT_WRITEDELAY;
90
91 /* Set the function pointers */ 83 /* Set the function pointers */
92 this->OpenAudio = DUMMYAUD_OpenAudio; 84 this->OpenAudio = DUMMYAUD_OpenAudio;
93 this->WaitAudio = DUMMYAUD_WaitAudio; 85 this->WaitAudio = DUMMYAUD_WaitAudio;
94 this->PlayAudio = DUMMYAUD_PlayAudio; 86 this->PlayAudio = DUMMYAUD_PlayAudio;
95 this->GetAudioBuf = DUMMYAUD_GetAudioBuf; 87 this->GetAudioBuf = DUMMYAUD_GetAudioBuf;
106 }; 98 };
107 99
108 /* This function waits until it is possible to write a full sound buffer */ 100 /* This function waits until it is possible to write a full sound buffer */
109 static void DUMMYAUD_WaitAudio(_THIS) 101 static void DUMMYAUD_WaitAudio(_THIS)
110 { 102 {
111 SDL_Delay(this->hidden->write_delay); 103 /* Don't block on first calls to simulate initial fragment filling. */
104 if (this->hidden->initial_calls)
105 this->hidden->initial_calls--;
106 else
107 SDL_Delay(this->hidden->write_delay);
112 } 108 }
113 109
114 static void DUMMYAUD_PlayAudio(_THIS) 110 static void DUMMYAUD_PlayAudio(_THIS)
115 { 111 {
116 /* no-op...this is a null driver. */ 112 /* no-op...this is a null driver. */
117 } 113 }
118 114
119 static Uint8 *DUMMYAUD_GetAudioBuf(_THIS) 115 static Uint8 *DUMMYAUD_GetAudioBuf(_THIS)
120 { 116 {
121 return(this->hidden->mixbuf); 117 return(this->hidden->mixbuf);
129 } 125 }
130 } 126 }
131 127
132 static int DUMMYAUD_OpenAudio(_THIS, SDL_AudioSpec *spec) 128 static int DUMMYAUD_OpenAudio(_THIS, SDL_AudioSpec *spec)
133 { 129 {
130 float bytes_per_sec = 0.0f;
131
134 /* Allocate mixing buffer */ 132 /* Allocate mixing buffer */
135 this->hidden->mixlen = spec->size; 133 this->hidden->mixlen = spec->size;
136 this->hidden->mixbuf = (Uint8 *) SDL_AllocAudioMem(this->hidden->mixlen); 134 this->hidden->mixbuf = (Uint8 *) SDL_AllocAudioMem(this->hidden->mixlen);
137 if ( this->hidden->mixbuf == NULL ) { 135 if ( this->hidden->mixbuf == NULL ) {
138 return(-1); 136 return(-1);
139 } 137 }
140 SDL_memset(this->hidden->mixbuf, spec->silence, spec->size); 138 SDL_memset(this->hidden->mixbuf, spec->silence, spec->size);
141 139
140 bytes_per_sec = (float) (((spec->format & 0xFF) / 8) *
141 spec->channels * spec->freq);
142
143 /*
144 * We try to make this request more audio at the correct rate for
145 * a given audio spec, so timing stays fairly faithful.
146 * Also, we have it not block at all for the first two calls, so
147 * it seems like we're filling two audio fragments right out of the
148 * gate, like other SDL drivers tend to do.
149 */
150 this->hidden->initial_calls = 2;
151 this->hidden->write_delay =
152 (Uint32) ((((float) spec->size) / bytes_per_sec) * 1000.0f);
153
142 /* We're ready to rock and roll. :-) */ 154 /* We're ready to rock and roll. :-) */
143 return(0); 155 return(0);
144 } 156 }
145 157