2 * OpenAL Loopback Example
4 * Copyright (c) 2013 by Chris Robinson <chris.kcat@gmail.com>
6 * Permission is hereby granted, free of charge, to any person obtaining a copy
7 * of this software and associated documentation files (the "Software"), to deal
8 * in the Software without restriction, including without limitation the rights
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10 * copies of the Software, and to permit persons to whom the Software is
11 * furnished to do so, subject to the following conditions:
13 * The above copyright notice and this permission notice shall be included in
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16 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
17 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
18 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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21 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
25 /* This file contains an example for using the loopback device for custom
39 #include "common/alhelpers.h"
42 #define M_PI (3.14159265358979323846)
52 static LPALCLOOPBACKOPENDEVICESOFT alcLoopbackOpenDeviceSOFT
;
53 static LPALCISRENDERFORMATSUPPORTEDSOFT alcIsRenderFormatSupportedSOFT
;
54 static LPALCRENDERSAMPLESSOFT alcRenderSamplesSOFT
;
57 void SDLCALL
RenderSDLSamples(void *userdata
, Uint8
*stream
, int len
)
59 PlaybackInfo
*playback
= (PlaybackInfo
*)userdata
;
60 alcRenderSamplesSOFT(playback
->Device
, stream
, len
/playback
->FrameSize
);
64 /* Creates a one second buffer containing a sine wave, and returns the new
66 static ALuint
CreateSineWave(void)
73 for(i
= 0;i
< 44100;i
++)
74 data
[i
] = (ALshort
)(sin(i
* 441.0 / 44100.0 * 2.0*M_PI
)*32767.0);
76 /* Buffer the audio data into a new buffer object. */
78 alGenBuffers(1, &buffer
);
79 alBufferData(buffer
, AL_FORMAT_MONO16
, data
, sizeof(data
), 44100);
81 /* Check if an error occured, and clean up if so. */
83 if(err
!= AL_NO_ERROR
)
85 fprintf(stderr
, "OpenAL Error: %s\n", alGetString(err
));
86 if(alIsBuffer(buffer
))
87 alDeleteBuffers(1, &buffer
);
97 PlaybackInfo playback
= { NULL
, NULL
, 0 };
98 SDL_AudioSpec desired
, obtained
;
99 ALuint source
, buffer
;
103 /* Print out error if extension is missing. */
104 if(!alcIsExtensionPresent(NULL
, "ALC_SOFT_loopback"))
106 fprintf(stderr
, "Error: ALC_SOFT_loopback not supported!\n");
110 /* Define a macro to help load the function pointers. */
111 #define LOAD_PROC(x) ((x) = alcGetProcAddress(NULL, #x))
112 LOAD_PROC(alcLoopbackOpenDeviceSOFT
);
113 LOAD_PROC(alcIsRenderFormatSupportedSOFT
);
114 LOAD_PROC(alcRenderSamplesSOFT
);
117 if(SDL_Init(SDL_INIT_AUDIO
) == -1)
119 fprintf(stderr
, "Failed to init SDL audio: %s\n", SDL_GetError());
123 /* Set up SDL audio with our requested format and callback. */
124 desired
.channels
= 2;
125 desired
.format
= AUDIO_S16SYS
;
126 desired
.freq
= 44100;
128 desired
.samples
= 4096;
129 desired
.callback
= RenderSDLSamples
;
130 desired
.userdata
= &playback
;
131 if(SDL_OpenAudio(&desired
, &obtained
) != 0)
134 fprintf(stderr
, "Failed to open SDL audio: %s\n", SDL_GetError());
138 /* Set up our OpenAL attributes based on what we got from SDL. */
139 attrs
[0] = ALC_FORMAT_CHANNELS_SOFT
;
140 if(obtained
.channels
== 1)
141 attrs
[1] = ALC_MONO_SOFT
;
142 else if(obtained
.channels
== 2)
143 attrs
[1] = ALC_STEREO_SOFT
;
146 fprintf(stderr
, "Unhandled SDL channel count: %d\n", obtained
.channels
);
150 attrs
[2] = ALC_FORMAT_TYPE_SOFT
;
151 if(obtained
.format
== AUDIO_U8
)
152 attrs
[3] = ALC_UNSIGNED_BYTE_SOFT
;
153 else if(obtained
.format
== AUDIO_S8
)
154 attrs
[3] = ALC_BYTE_SOFT
;
155 else if(obtained
.format
== AUDIO_U16SYS
)
156 attrs
[3] = ALC_UNSIGNED_SHORT_SOFT
;
157 else if(obtained
.format
== AUDIO_S16SYS
)
158 attrs
[3] = ALC_SHORT_SOFT
;
161 fprintf(stderr
, "Unhandled SDL format: 0x%04x\n", obtained
.format
);
165 attrs
[4] = ALC_FREQUENCY
;
166 attrs
[5] = obtained
.freq
;
168 attrs
[6] = 0; /* end of list */
170 /* Initialize OpenAL loopback device, using our format attributes. */
171 playback
.Device
= alcLoopbackOpenDeviceSOFT(NULL
);
174 fprintf(stderr
, "Failed to open loopback device!\n");
177 /* Make sure the format is supported before setting them on the device. */
178 if(alcIsRenderFormatSupportedSOFT(playback
.Device
, attrs
[5], attrs
[1], attrs
[3]) == ALC_FALSE
)
180 fprintf(stderr
, "Render format not supported: %s, %s, %dhz\n",
181 ChannelsName(attrs
[1]), TypeName(attrs
[3]), attrs
[5]);
184 playback
.Context
= alcCreateContext(playback
.Device
, attrs
);
185 if(!playback
.Context
|| alcMakeContextCurrent(playback
.Context
) == ALC_FALSE
)
187 fprintf(stderr
, "Failed to set an OpenAL audio context\n");
190 playback
.FrameSize
= FramesToBytes(1, attrs
[1], attrs
[3]);
192 /* Start SDL playing. Our callback (thus alcRenderSamplesSOFT) will now
193 * start being called regularly to update the AL playback state. */
196 /* Load the sound into a buffer. */
197 buffer
= CreateSineWave();
201 alcDestroyContext(playback
.Context
);
202 alcCloseDevice(playback
.Device
);
207 /* Create the source to play the sound with. */
209 alGenSources(1, &source
);
210 alSourcei(source
, AL_BUFFER
, buffer
);
211 assert(alGetError()==AL_NO_ERROR
&& "Failed to setup sound source");
213 /* Play the sound until it finishes. */
214 alSourcePlay(source
);
217 alGetSourcei(source
, AL_SOURCE_STATE
, &state
);
218 } while(alGetError() == AL_NO_ERROR
&& state
== AL_PLAYING
);
220 /* All done. Delete resources, and close OpenAL. */
221 alDeleteSources(1, &source
);
222 alDeleteBuffers(1, &buffer
);
224 /* Stop SDL playing. */
227 /* Close up OpenAL and SDL. */
229 alcDestroyContext(playback
.Context
);
230 alcCloseDevice(playback
.Device
);
238 alcDestroyContext(playback
.Context
);
240 alcCloseDevice(playback
.Device
);