Add a loopback extension example

1 files changed, 244 insertions, 0 deletions

diff --git a/examples/alloopback.c b/examples/alloopback.c
new file mode 100644
index 00000000..649ef6ef
--- /dev/null
+++ b/examples/alloopback.c
@@ -0,0 +1,244 @@
+/*
+ * OpenAL Loopback Example
+ *
+ * Copyright (c) 2013 by Chris Robinson <[email protected]>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+/* This file contains an example for using the loopback device for custom
+ * output handling.
+ */
+
+#include <stdio.h>
+#include <assert.h>
+#include <math.h>
+
+#include <SDL.h>
+
+#include "AL/al.h"
+#include "AL/alc.h"
+#include "AL/alext.h"
+
+#include "common/alhelpers.h"
+
+#ifndef M_PI
+#define M_PI    (3.14159265358979323846)
+#endif
+
+typedef struct {
+    ALCdevice *Device;
+    ALCcontext *Context;
+
+    ALCsizei FrameSize;
+} PlaybackInfo;
+
+static LPALCLOOPBACKOPENDEVICESOFT alcLoopbackOpenDeviceSOFT;
+static LPALCISRENDERFORMATSUPPORTEDSOFT alcIsRenderFormatSupportedSOFT;
+static LPALCRENDERSAMPLESSOFT alcRenderSamplesSOFT;
+
+
+void SDLCALL RenderSDLSamples(void *userdata, Uint8 *stream, int len)
+{
+    PlaybackInfo *playback = (PlaybackInfo*)userdata;
+    alcRenderSamplesSOFT(playback->Device, stream, len/playback->FrameSize);
+}
+
+
+/* Creates a one second buffer containing a sine wave, and returns the new
+ * buffer ID. */
+static ALuint CreateSineWave(void)
+{
+    ALshort data[44100];
+    ALuint buffer;
+    ALenum err;
+    ALuint i;
+
+    for(i = 0;i < 44100;i++)
+        data[i] = (ALshort)(sin(i * 441.0 / 44100.0 * 2.0*M_PI)*32767.0);
+
+    /* Buffer the audio data into a new buffer object. */
+    buffer = 0;
+    alGenBuffers(1, &buffer);
+    alBufferData(buffer, AL_FORMAT_MONO16, data, sizeof(data), 44100);
+
+    /* Check if an error occured, and clean up if so. */
+    err = alGetError();
+    if(err != AL_NO_ERROR)
+    {
+        fprintf(stderr, "OpenAL Error: %s\n", alGetString(err));
+        if(alIsBuffer(buffer))
+            alDeleteBuffers(1, &buffer);
+        return 0;
+    }
+
+    return buffer;
+}
+
+
+int main()
+{
+    PlaybackInfo playback = { NULL, NULL, 0 };
+    SDL_AudioSpec desired, obtained;
+    ALuint source, buffer;
+    ALCint attrs[16];
+    ALenum state;
+
+    /* Print out error if extension is missing. */
+    if(!alcIsExtensionPresent(NULL, "ALC_SOFT_loopback"))
+    {
+        fprintf(stderr, "Error: ALC_SOFT_loopback not supported!\n");
+        return 1;
+    }
+
+    /* Define a macro to help load the function pointers. */
+#define LOAD_PROC(x)  ((x) = alcGetProcAddress(NULL, #x))
+    LOAD_PROC(alcLoopbackOpenDeviceSOFT);
+    LOAD_PROC(alcIsRenderFormatSupportedSOFT);
+    LOAD_PROC(alcRenderSamplesSOFT);
+#undef LOAD_PROC
+
+    if(SDL_Init(SDL_INIT_AUDIO) == -1)
+    {
+        fprintf(stderr, "Failed to init SDL audio: %s\n", SDL_GetError());
+        return 1;
+    }
+
+    /* Set up SDL audio with our requested format and callback. */
+    desired.channels = 2;
+    desired.format = AUDIO_S16SYS;
+    desired.freq = 44100;
+    desired.padding = 0;
+    desired.samples = 4096;
+    desired.callback = RenderSDLSamples;
+    desired.userdata = &playback;
+    if(SDL_OpenAudio(&desired, &obtained) != 0)
+    {
+        SDL_Quit();
+        fprintf(stderr, "Failed to open SDL audio: %s\n", SDL_GetError());
+        return 1;
+    }
+
+    /* Set up our OpenAL attributes based on what we got from SDL. */
+    attrs[0] = ALC_FORMAT_CHANNELS_SOFT;
+    if(obtained.channels == 1)
+        attrs[1] = ALC_MONO_SOFT;
+    else if(obtained.channels == 2)
+        attrs[1] = ALC_STEREO_SOFT;
+    else
+    {
+        fprintf(stderr, "Unhandled SDL channel count: %d\n", obtained.channels);
+        goto error;
+    }
+
+    attrs[2] = ALC_FORMAT_TYPE_SOFT;
+    if(obtained.format == AUDIO_U8)
+        attrs[3] = ALC_UNSIGNED_BYTE_SOFT;
+    else if(obtained.format == AUDIO_S8)
+        attrs[3] = ALC_BYTE_SOFT;
+    else if(obtained.format == AUDIO_U16SYS)
+        attrs[3] = ALC_UNSIGNED_SHORT_SOFT;
+    else if(obtained.format == AUDIO_S16SYS)
+        attrs[3] = ALC_SHORT_SOFT;
+    else
+    {
+        fprintf(stderr, "Unhandled SDL format: 0x%04x\n", obtained.format);
+        goto error;
+    }
+
+    attrs[4] = ALC_FREQUENCY;
+    attrs[5] = obtained.freq;
+
+    attrs[6] = 0; /* end of list */
+
+    /* Initialize OpenAL loopback device, using our format attributes. */
+    playback.Device = alcLoopbackOpenDeviceSOFT(NULL);
+    if(!playback.Device)
+    {
+        fprintf(stderr, "Failed to open loopback device!\n");
+        goto error;
+    }
+    /* Make sure the format is supported before setting them on the device. */
+    if(alcIsRenderFormatSupportedSOFT(playback.Device, attrs[5], attrs[1], attrs[3]) == ALC_FALSE)
+    {
+        fprintf(stderr, "Render format not supported: %s, %s, %dhz\n",
+                        ChannelsName(attrs[1]), TypeName(attrs[3]), attrs[5]);
+        goto error;
+    }
+    playback.Context = alcCreateContext(playback.Device, attrs);
+    if(!playback.Context || alcMakeContextCurrent(playback.Context) == ALC_FALSE)
+    {
+        fprintf(stderr, "Failed to set an OpenAL audio context\n");
+        goto error;
+    }
+    playback.FrameSize = FramesToBytes(1, attrs[1], attrs[3]);
+
+    /* Start SDL playing. Our callback (thus alcRenderSamplesSOFT) will now
+     * start being called regularly to update the AL playback state. */
+    SDL_PauseAudio(0);
+
+    /* Load the sound into a buffer. */
+    buffer = CreateSineWave();
+    if(!buffer)
+    {
+        SDL_CloseAudio();
+        alcDestroyContext(playback.Context);
+        alcCloseDevice(playback.Device);
+        SDL_Quit();
+        return 1;
+    }
+
+    /* Create the source to play the sound with. */
+    source = 0;
+    alGenSources(1, &source);
+    alSourcei(source, AL_BUFFER, buffer);
+    assert(alGetError()==AL_NO_ERROR && "Failed to setup sound source");
+
+    /* Play the sound until it finishes. */
+    alSourcePlay(source);
+    do {
+        Sleep(10);
+        alGetSourcei(source, AL_SOURCE_STATE, &state);
+    } while(alGetError() == AL_NO_ERROR && state == AL_PLAYING);
+
+    /* All done. Delete resources, and close OpenAL. */
+    alDeleteSources(1, &source);
+    alDeleteBuffers(1, &buffer);
+
+    /* Stop SDL playing. */
+    SDL_PauseAudio(1);
+
+    /* Close up OpenAL and SDL. */
+    SDL_CloseAudio();
+    alcDestroyContext(playback.Context);
+    alcCloseDevice(playback.Device);
+    SDL_Quit();
+
+    return 0;
+
+error:
+    SDL_CloseAudio();
+    if(playback.Context)
+        alcDestroyContext(playback.Context);
+    if(playback.Device)
+        alcCloseDevice(playback.Device);
+    SDL_Quit();
+
+    return 1;
+}