Move backend sources to a separate sub-directory

1 files changed, 719 insertions, 0 deletions

diff --git a/Alc/backends/coreaudio.c b/Alc/backends/coreaudio.c
new file mode 100644
index 00000000..c84be846
--- /dev/null
+++ b/Alc/backends/coreaudio.c
@@ -0,0 +1,719 @@
+/**
+ * OpenAL cross platform audio library
+ * Copyright (C) 1999-2007 by authors.
+ * This library is free software; you can redistribute it and/or
+ *  modify it under the terms of the GNU Library General Public
+ *  License as published by the Free Software Foundation; either
+ *  version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ *  Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ *  License along with this library; if not, write to the
+ *  Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ *  Boston, MA  02111-1307, USA.
+ * Or go to http://www.gnu.org/copyleft/lgpl.html
+ */
+
+#include "config.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "alMain.h"
+#include "AL/al.h"
+#include "AL/alc.h"
+
+#include <CoreServices/CoreServices.h>
+#include <unistd.h>
+#include <AudioUnit/AudioUnit.h>
+#include <AudioToolbox/AudioToolbox.h>
+
+
+typedef struct {
+    AudioUnit audioUnit;
+
+    ALuint frameSize;
+    ALdouble sampleRateRatio;              // Ratio of hardware sample rate / requested sample rate
+    AudioStreamBasicDescription format;    // This is the OpenAL format as a CoreAudio ASBD
+
+    AudioConverterRef audioConverter;      // Sample rate converter if needed
+    AudioBufferList *bufferList;           // Buffer for data coming from the input device
+    ALCvoid *resampleBuffer;               // Buffer for returned RingBuffer data when resampling
+
+    RingBuffer *ring;
+} ca_data;
+
+static const ALCchar ca_device[] = "CoreAudio Default";
+
+
+static void destroy_buffer_list(AudioBufferList* list)
+{
+    if(list)
+    {
+        UInt32 i;
+        for(i = 0;i < list->mNumberBuffers;i++)
+            free(list->mBuffers[i].mData);
+        free(list);
+    }
+}
+
+static AudioBufferList* allocate_buffer_list(UInt32 channelCount, UInt32 byteSize)
+{
+    AudioBufferList *list;
+
+    list = calloc(1, sizeof(AudioBufferList) + sizeof(AudioBuffer));
+    if(list)
+    {
+        list->mNumberBuffers = 1;
+
+        list->mBuffers[0].mNumberChannels = channelCount;
+        list->mBuffers[0].mDataByteSize = byteSize;
+        list->mBuffers[0].mData = malloc(byteSize);
+        if(list->mBuffers[0].mData == NULL)
+        {
+            free(list);
+            list = NULL;
+        }
+    }
+    return list;
+}
+
+static OSStatus ca_callback(void *inRefCon, AudioUnitRenderActionFlags *ioActionFlags, const AudioTimeStamp *inTimeStamp,
+                            UInt32 inBusNumber, UInt32 inNumberFrames, AudioBufferList *ioData)
+{
+    ALCdevice *device = (ALCdevice*)inRefCon;
+    ca_data *data = (ca_data*)device->ExtraData;
+
+    aluMixData(device, ioData->mBuffers[0].mData,
+               ioData->mBuffers[0].mDataByteSize / data->frameSize);
+
+    return noErr;
+}
+
+static OSStatus ca_capture_conversion_callback(AudioConverterRef inAudioConverter, UInt32 *ioNumberDataPackets,
+        AudioBufferList *ioData, AudioStreamPacketDescription **outDataPacketDescription, void* inUserData)
+{
+    ALCdevice *device = (ALCdevice*)inUserData;
+    ca_data *data = (ca_data*)device->ExtraData;
+
+    // Read from the ring buffer and store temporarily in a large buffer
+    ReadRingBuffer(data->ring, data->resampleBuffer, (ALsizei)(*ioNumberDataPackets));
+
+    // Set the input data
+    ioData->mNumberBuffers = 1;
+    ioData->mBuffers[0].mNumberChannels = data->format.mChannelsPerFrame;
+    ioData->mBuffers[0].mData = data->resampleBuffer;
+    ioData->mBuffers[0].mDataByteSize = (*ioNumberDataPackets) * data->format.mBytesPerFrame;
+
+    return noErr;
+}
+
+static OSStatus ca_capture_callback(void *inRefCon, AudioUnitRenderActionFlags *ioActionFlags,
+                                    const AudioTimeStamp *inTimeStamp, UInt32 inBusNumber,
+                                    UInt32 inNumberFrames, AudioBufferList *ioData)
+{
+    ALCdevice *device = (ALCdevice*)inRefCon;
+    ca_data *data = (ca_data*)device->ExtraData;
+    AudioUnitRenderActionFlags flags = 0;
+    OSStatus err;
+
+    // fill the bufferList with data from the input device
+    err = AudioUnitRender(data->audioUnit, &flags, inTimeStamp, 1, inNumberFrames, data->bufferList);
+    if(err != noErr)
+    {
+        ERR("AudioUnitRender error: %d\n", err);
+        return err;
+    }
+
+    WriteRingBuffer(data->ring, data->bufferList->mBuffers[0].mData, inNumberFrames);
+
+    return noErr;
+}
+
+static ALCboolean ca_open_playback(ALCdevice *device, const ALCchar *deviceName)
+{
+    ComponentDescription desc;
+    Component comp;
+    ca_data *data;
+    OSStatus err;
+
+    if(!deviceName)
+        deviceName = ca_device;
+    else if(strcmp(deviceName, ca_device) != 0)
+        return ALC_FALSE;
+
+    /* open the default output unit */
+    desc.componentType = kAudioUnitType_Output;
+    desc.componentSubType = kAudioUnitSubType_DefaultOutput;
+    desc.componentManufacturer = kAudioUnitManufacturer_Apple;
+    desc.componentFlags = 0;
+    desc.componentFlagsMask = 0;
+
+    comp = FindNextComponent(NULL, &desc);
+    if(comp == NULL)
+    {
+        ERR("FindNextComponent failed\n");
+        return ALC_FALSE;
+    }
+
+    data = calloc(1, sizeof(*data));
+    device->ExtraData = data;
+
+    err = OpenAComponent(comp, &data->audioUnit);
+    if(err != noErr)
+    {
+        ERR("OpenAComponent failed\n");
+        free(data);
+        device->ExtraData = NULL;
+        return ALC_FALSE;
+    }
+
+    return ALC_TRUE;
+}
+
+static void ca_close_playback(ALCdevice *device)
+{
+    ca_data *data = (ca_data*)device->ExtraData;
+
+    CloseComponent(data->audioUnit);
+
+    free(data);
+    device->ExtraData = NULL;
+}
+
+static ALCboolean ca_reset_playback(ALCdevice *device)
+{
+    ca_data *data = (ca_data*)device->ExtraData;
+    AudioStreamBasicDescription streamFormat;
+    AURenderCallbackStruct input;
+    OSStatus err;
+    UInt32 size;
+
+    /* init and start the default audio unit... */
+    err = AudioUnitInitialize(data->audioUnit);
+    if(err != noErr)
+    {
+        ERR("AudioUnitInitialize failed\n");
+        return ALC_FALSE;
+    }
+
+    err = AudioOutputUnitStart(data->audioUnit);
+    if(err != noErr)
+    {
+        ERR("AudioOutputUnitStart failed\n");
+        return ALC_FALSE;
+    }
+
+    /* retrieve default output unit's properties (output side) */
+    size = sizeof(AudioStreamBasicDescription);
+    err = AudioUnitGetProperty(data->audioUnit, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Output, 0, &streamFormat, &size);
+    if(err != noErr || size != sizeof(AudioStreamBasicDescription))
+    {
+        ERR("AudioUnitGetProperty failed\n");
+        return ALC_FALSE;
+    }
+
+#if 0
+    TRACE("Output streamFormat of default output unit -\n");
+    TRACE("  streamFormat.mFramesPerPacket = %d\n", streamFormat.mFramesPerPacket);
+    TRACE("  streamFormat.mChannelsPerFrame = %d\n", streamFormat.mChannelsPerFrame);
+    TRACE("  streamFormat.mBitsPerChannel = %d\n", streamFormat.mBitsPerChannel);
+    TRACE("  streamFormat.mBytesPerPacket = %d\n", streamFormat.mBytesPerPacket);
+    TRACE("  streamFormat.mBytesPerFrame = %d\n", streamFormat.mBytesPerFrame);
+    TRACE("  streamFormat.mSampleRate = %5.0f\n", streamFormat.mSampleRate);
+#endif
+
+    /* set default output unit's input side to match output side */
+    err = AudioUnitSetProperty(data->audioUnit, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Input, 0, &streamFormat, size);
+    if(err != noErr)
+    {
+        ERR("AudioUnitSetProperty failed\n");
+        return ALC_FALSE;
+    }
+
+    if(device->Frequency != streamFormat.mSampleRate)
+    {
+        if((device->Flags&DEVICE_FREQUENCY_REQUEST))
+            ERR("CoreAudio does not support changing sample rates (wanted %dhz, got %dhz)\n", device->Frequency, streamFormat.mSampleRate);
+        device->Flags &= ~DEVICE_FREQUENCY_REQUEST;
+
+        device->UpdateSize = (ALuint)((ALuint64)device->UpdateSize *
+                                      streamFormat.mSampleRate /
+                                      device->Frequency);
+        device->Frequency = streamFormat.mSampleRate;
+    }
+
+    /* FIXME: How to tell what channels are what in the output device, and how
+     * to specify what we're giving?  eg, 6.0 vs 5.1 */
+    switch(streamFormat.mChannelsPerFrame)
+    {
+        case 1:
+            if((device->Flags&DEVICE_CHANNELS_REQUEST) &&
+               device->FmtChans != DevFmtMono)
+            {
+                ERR("Failed to set %s, got Mono instead\n", DevFmtChannelsString(device->FmtChans));
+                device->Flags &= ~DEVICE_CHANNELS_REQUEST;
+            }
+            device->FmtChans = DevFmtMono;
+            break;
+        case 2:
+            if((device->Flags&DEVICE_CHANNELS_REQUEST) &&
+               device->FmtChans != DevFmtStereo)
+            {
+                ERR("Failed to set %s, got Stereo instead\n", DevFmtChannelsString(device->FmtChans));
+                device->Flags &= ~DEVICE_CHANNELS_REQUEST;
+            }
+            device->FmtChans = DevFmtStereo;
+            break;
+        case 4:
+            if((device->Flags&DEVICE_CHANNELS_REQUEST) &&
+               device->FmtChans != DevFmtQuad)
+            {
+                ERR("Failed to set %s, got Quad instead\n", DevFmtChannelsString(device->FmtChans));
+                device->Flags &= ~DEVICE_CHANNELS_REQUEST;
+            }
+            device->FmtChans = DevFmtQuad;
+            break;
+        case 6:
+            if((device->Flags&DEVICE_CHANNELS_REQUEST) &&
+               device->FmtChans != DevFmtX51)
+            {
+                ERR("Failed to set %s, got 5.1 Surround instead\n", DevFmtChannelsString(device->FmtChans));
+                device->Flags &= ~DEVICE_CHANNELS_REQUEST;
+            }
+            device->FmtChans = DevFmtX51;
+            break;
+        case 7:
+            if((device->Flags&DEVICE_CHANNELS_REQUEST) &&
+               device->FmtChans != DevFmtX61)
+            {
+                ERR("Failed to set %s, got 6.1 Surround instead\n", DevFmtChannelsString(device->FmtChans));
+                device->Flags &= ~DEVICE_CHANNELS_REQUEST;
+            }
+            device->FmtChans = DevFmtX61;
+            break;
+        case 8:
+            if((device->Flags&DEVICE_CHANNELS_REQUEST) &&
+               device->FmtChans != DevFmtX71)
+            {
+                ERR("Failed to set %s, got 7.1 Surround instead\n", DevFmtChannelsString(device->FmtChans));
+                device->Flags &= ~DEVICE_CHANNELS_REQUEST;
+            }
+            device->FmtChans = DevFmtX71;
+            break;
+        default:
+            ERR("Unhandled channel count (%d), using Stereo\n", streamFormat.mChannelsPerFrame);
+            device->Flags &= ~DEVICE_CHANNELS_REQUEST;
+            device->FmtChans = DevFmtStereo;
+            streamFormat.mChannelsPerFrame = 2;
+            break;
+    }
+    SetDefaultWFXChannelOrder(device);
+
+    /* use channel count and sample rate from the default output unit's current
+     * parameters, but reset everything else */
+    streamFormat.mFramesPerPacket = 1;
+    switch(device->FmtType)
+    {
+        case DevFmtUByte:
+            device->FmtType = DevFmtByte;
+            /* fall-through */
+        case DevFmtByte:
+            streamFormat.mBitsPerChannel = 8;
+            streamFormat.mBytesPerPacket = streamFormat.mChannelsPerFrame;
+            streamFormat.mBytesPerFrame = streamFormat.mChannelsPerFrame;
+            break;
+        case DevFmtUShort:
+        case DevFmtFloat:
+            device->FmtType = DevFmtShort;
+            /* fall-through */
+        case DevFmtShort:
+            streamFormat.mBitsPerChannel = 16;
+            streamFormat.mBytesPerPacket = 2 * streamFormat.mChannelsPerFrame;
+            streamFormat.mBytesPerFrame = 2 * streamFormat.mChannelsPerFrame;
+            break;
+    }
+    streamFormat.mFormatID = kAudioFormatLinearPCM;
+    streamFormat.mFormatFlags = kLinearPCMFormatFlagIsSignedInteger |
+                                kAudioFormatFlagsNativeEndian |
+                                kLinearPCMFormatFlagIsPacked;
+
+    err = AudioUnitSetProperty(data->audioUnit, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Input, 0, &streamFormat, sizeof(AudioStreamBasicDescription));
+    if(err != noErr)
+    {
+        ERR("AudioUnitSetProperty failed\n");
+        return ALC_FALSE;
+    }
+
+    /* setup callback */
+    data->frameSize = FrameSizeFromDevFmt(device->FmtChans, device->FmtType);
+    input.inputProc = ca_callback;
+    input.inputProcRefCon = device;
+
+    err = AudioUnitSetProperty(data->audioUnit, kAudioUnitProperty_SetRenderCallback, kAudioUnitScope_Input, 0, &input, sizeof(AURenderCallbackStruct));
+    if(err != noErr)
+    {
+        ERR("AudioUnitSetProperty failed\n");
+        return ALC_FALSE;
+    }
+
+    return ALC_TRUE;
+}
+
+static void ca_stop_playback(ALCdevice *device)
+{
+    ca_data *data = (ca_data*)device->ExtraData;
+    OSStatus err;
+
+    AudioOutputUnitStop(data->audioUnit);
+    err = AudioUnitUninitialize(data->audioUnit);
+    if(err != noErr)
+        ERR("-- AudioUnitUninitialize failed.\n");
+}
+
+static ALCboolean ca_open_capture(ALCdevice *device, const ALCchar *deviceName)
+{
+    AudioStreamBasicDescription requestedFormat;  // The application requested format
+    AudioStreamBasicDescription hardwareFormat;   // The hardware format
+    AudioStreamBasicDescription outputFormat;     // The AudioUnit output format
+    AURenderCallbackStruct input;
+    ComponentDescription desc;
+    AudioDeviceID inputDevice;
+    UInt32 outputFrameCount;
+    UInt32 propertySize;
+    UInt32 enableIO;
+    Component comp;
+    ca_data *data;
+    OSStatus err;
+
+    desc.componentType = kAudioUnitType_Output;
+    desc.componentSubType = kAudioUnitSubType_HALOutput;
+    desc.componentManufacturer = kAudioUnitManufacturer_Apple;
+    desc.componentFlags = 0;
+    desc.componentFlagsMask = 0;
+
+    // Search for component with given description
+    comp = FindNextComponent(NULL, &desc);
+    if(comp == NULL)
+    {
+        ERR("FindNextComponent failed\n");
+        return ALC_FALSE;
+    }
+
+    data = calloc(1, sizeof(*data));
+    device->ExtraData = data;
+
+    // Open the component
+    err = OpenAComponent(comp, &data->audioUnit);
+    if(err != noErr)
+    {
+        ERR("OpenAComponent failed\n");
+        goto error;
+    }
+
+    // Turn off AudioUnit output
+    enableIO = 0;
+    err = AudioUnitSetProperty(data->audioUnit, kAudioOutputUnitProperty_EnableIO, kAudioUnitScope_Output, 0, &enableIO, sizeof(ALuint));
+    if(err != noErr)
+    {
+        ERR("AudioUnitSetProperty failed\n");
+        goto error;
+    }
+
+    // Turn on AudioUnit input
+    enableIO = 1;
+    err = AudioUnitSetProperty(data->audioUnit, kAudioOutputUnitProperty_EnableIO, kAudioUnitScope_Input, 1, &enableIO, sizeof(ALuint));
+    if(err != noErr)
+    {
+        ERR("AudioUnitSetProperty failed\n");
+        goto error;
+    }
+
+    // Get the default input device
+    propertySize = sizeof(AudioDeviceID);
+    err = AudioHardwareGetProperty(kAudioHardwarePropertyDefaultInputDevice, &propertySize, &inputDevice);
+    if(err != noErr)
+    {
+        ERR("AudioHardwareGetProperty failed\n");
+        goto error;
+    }
+
+    if(inputDevice == kAudioDeviceUnknown)
+    {
+        ERR("No input device found\n");
+        goto error;
+    }
+
+    // Track the input device
+    err = AudioUnitSetProperty(data->audioUnit, kAudioOutputUnitProperty_CurrentDevice, kAudioUnitScope_Global, 0, &inputDevice, sizeof(AudioDeviceID));
+    if(err != noErr)
+    {
+        ERR("AudioUnitSetProperty failed\n");
+        goto error;
+    }
+
+    // set capture callback
+    input.inputProc = ca_capture_callback;
+    input.inputProcRefCon = device;
+
+    err = AudioUnitSetProperty(data->audioUnit, kAudioOutputUnitProperty_SetInputCallback, kAudioUnitScope_Global, 0, &input, sizeof(AURenderCallbackStruct));
+    if(err != noErr)
+    {
+        ERR("AudioUnitSetProperty failed\n");
+        goto error;
+    }
+
+    // Initialize the device
+    err = AudioUnitInitialize(data->audioUnit);
+    if(err != noErr)
+    {
+        ERR("AudioUnitInitialize failed\n");
+        goto error;
+    }
+
+    // Get the hardware format
+    propertySize = sizeof(AudioStreamBasicDescription);
+    err = AudioUnitGetProperty(data->audioUnit, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Input, 1, &hardwareFormat, &propertySize);
+    if(err != noErr || propertySize != sizeof(AudioStreamBasicDescription))
+    {
+        ERR("AudioUnitGetProperty failed\n");
+        goto error;
+    }
+
+    // Set up the requested format description
+    switch(device->FmtType)
+    {
+        case DevFmtUByte:
+            requestedFormat.mBitsPerChannel = 8;
+            requestedFormat.mFormatFlags = kAudioFormatFlagIsPacked;
+            break;
+        case DevFmtShort:
+            requestedFormat.mBitsPerChannel = 16;
+            requestedFormat.mFormatFlags = kAudioFormatFlagIsSignedInteger | kAudioFormatFlagsNativeEndian | kAudioFormatFlagIsPacked;
+            break;
+        case DevFmtFloat:
+            requestedFormat.mBitsPerChannel = 32;
+            requestedFormat.mFormatFlags = kAudioFormatFlagIsPacked;
+            break;
+        case DevFmtByte:
+        case DevFmtUShort:
+            ERR("%s samples not supported\n", DevFmtTypeString(device->FmtType));
+            goto error;
+    }
+
+    switch(device->FmtChans)
+    {
+        case DevFmtMono:
+            requestedFormat.mChannelsPerFrame = 1;
+            break;
+        case DevFmtStereo:
+            requestedFormat.mChannelsPerFrame = 2;
+            break;
+
+        case DevFmtQuad:
+        case DevFmtX51:
+        case DevFmtX51Side:
+        case DevFmtX61:
+        case DevFmtX71:
+            ERR("%s not supported\n", DevFmtChannelsString(device->FmtChans));
+            goto error;
+    }
+
+    requestedFormat.mBytesPerFrame = requestedFormat.mChannelsPerFrame * requestedFormat.mBitsPerChannel / 8;
+    requestedFormat.mBytesPerPacket = requestedFormat.mBytesPerFrame;
+    requestedFormat.mSampleRate = device->Frequency;
+    requestedFormat.mFormatID = kAudioFormatLinearPCM;
+    requestedFormat.mReserved = 0;
+    requestedFormat.mFramesPerPacket = 1;
+
+    // save requested format description for later use
+    data->format = requestedFormat;
+    data->frameSize = FrameSizeFromDevFmt(device->FmtChans, device->FmtType);
+
+    // Use intermediate format for sample rate conversion (outputFormat)
+    // Set sample rate to the same as hardware for resampling later
+    outputFormat = requestedFormat;
+    outputFormat.mSampleRate = hardwareFormat.mSampleRate;
+
+    // Determine sample rate ratio for resampling
+    data->sampleRateRatio = outputFormat.mSampleRate / device->Frequency;
+
+    // The output format should be the requested format, but using the hardware sample rate
+    // This is because the AudioUnit will automatically scale other properties, except for sample rate
+    err = AudioUnitSetProperty(data->audioUnit, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Output, 1, (void *)&outputFormat, sizeof(outputFormat));
+    if(err != noErr)
+    {
+        ERR("AudioUnitSetProperty failed\n");
+        goto error;
+    }
+
+    // Set the AudioUnit output format frame count
+    outputFrameCount = device->UpdateSize * data->sampleRateRatio;
+    err = AudioUnitSetProperty(data->audioUnit, kAudioUnitProperty_MaximumFramesPerSlice, kAudioUnitScope_Output, 0, &outputFrameCount, sizeof(outputFrameCount));
+    if(err != noErr)
+    {
+        ERR("AudioUnitSetProperty failed: %d\n", err);
+        goto error;
+    }
+
+    // Set up sample converter
+    err = AudioConverterNew(&outputFormat, &requestedFormat, &data->audioConverter);
+    if(err != noErr)
+    {
+        ERR("AudioConverterNew failed: %d\n", err);
+        goto error;
+    }
+
+    // Create a buffer for use in the resample callback
+    data->resampleBuffer = malloc(device->UpdateSize * data->frameSize * data->sampleRateRatio);
+
+    // Allocate buffer for the AudioUnit output
+    data->bufferList = allocate_buffer_list(outputFormat.mChannelsPerFrame, device->UpdateSize * data->frameSize * data->sampleRateRatio);
+    if(data->bufferList == NULL)
+    {
+        alcSetError(device, ALC_OUT_OF_MEMORY);
+        goto error;
+    }
+
+    data->ring = CreateRingBuffer(data->frameSize, (device->UpdateSize * data->sampleRateRatio) * device->NumUpdates);
+    if(data->ring == NULL)
+    {
+        alcSetError(device, ALC_OUT_OF_MEMORY);
+        goto error;
+    }
+
+    return ALC_TRUE;
+
+error:
+    DestroyRingBuffer(data->ring);
+    free(data->resampleBuffer);
+    destroy_buffer_list(data->bufferList);
+
+    if(data->audioConverter)
+        AudioConverterDispose(data->audioConverter);
+    if(data->audioUnit)
+        CloseComponent(data->audioUnit);
+
+    free(data);
+    device->ExtraData = NULL;
+
+    return ALC_FALSE;
+}
+
+static void ca_close_capture(ALCdevice *device)
+{
+    ca_data *data = (ca_data*)device->ExtraData;
+
+    DestroyRingBuffer(data->ring);
+    free(data->resampleBuffer);
+    destroy_buffer_list(data->bufferList);
+
+    AudioConverterDispose(data->audioConverter);
+    CloseComponent(data->audioUnit);
+
+    free(data);
+    device->ExtraData = NULL;
+}
+
+static void ca_start_capture(ALCdevice *device)
+{
+    ca_data *data = (ca_data*)device->ExtraData;
+    OSStatus err = AudioOutputUnitStart(data->audioUnit);
+    if(err != noErr)
+        ERR("AudioOutputUnitStart failed\n");
+}
+
+static void ca_stop_capture(ALCdevice *device)
+{
+    ca_data *data = (ca_data*)device->ExtraData;
+    OSStatus err = AudioOutputUnitStop(data->audioUnit);
+    if(err != noErr)
+        ERR("AudioOutputUnitStop failed\n");
+}
+
+static ALCuint ca_available_samples(ALCdevice *device)
+{
+    ca_data *data = device->ExtraData;
+    return RingBufferSize(data->ring) / data->sampleRateRatio;
+}
+
+static void ca_capture_samples(ALCdevice *device, ALCvoid *buffer, ALCuint samples)
+{
+    ca_data *data = (ca_data*)device->ExtraData;
+
+    if(samples <= ca_available_samples(device))
+    {
+        AudioBufferList *list;
+        UInt32 frameCount;
+        OSStatus err;
+
+        // If no samples are requested, just return
+        if(samples == 0)
+            return;
+
+        // Allocate a temporary AudioBufferList to use as the return resamples data
+        list = alloca(sizeof(AudioBufferList) + sizeof(AudioBuffer));
+
+        // Point the resampling buffer to the capture buffer
+        list->mNumberBuffers = 1;
+        list->mBuffers[0].mNumberChannels = data->format.mChannelsPerFrame;
+        list->mBuffers[0].mDataByteSize = samples * data->frameSize;
+        list->mBuffers[0].mData = buffer;
+
+        // Resample into another AudioBufferList
+        frameCount = samples;
+        err = AudioConverterFillComplexBuffer(data->audioConverter, ca_capture_conversion_callback, device,
+                                              &frameCount, list, NULL);
+        if(err != noErr)
+        {
+            ERR("AudioConverterFillComplexBuffer error: %d\n", err);
+            alcSetError(device, ALC_INVALID_VALUE);
+        }
+    }
+    else
+        alcSetError(device, ALC_INVALID_VALUE);
+}
+
+static const BackendFuncs ca_funcs = {
+    ca_open_playback,
+    ca_close_playback,
+    ca_reset_playback,
+    ca_stop_playback,
+    ca_open_capture,
+    ca_close_capture,
+    ca_start_capture,
+    ca_stop_capture,
+    ca_capture_samples,
+    ca_available_samples
+};
+
+ALCboolean alc_ca_init(BackendFuncs *func_list)
+{
+    *func_list = ca_funcs;
+    return ALC_TRUE;
+}
+
+void alc_ca_deinit(void)
+{
+}
+
+void alc_ca_probe(enum DevProbe type)
+{
+    switch(type)
+    {
+        case DEVICE_PROBE:
+            AppendDeviceList(ca_device);
+            break;
+        case ALL_DEVICE_PROBE:
+            AppendAllDeviceList(ca_device);
+            break;
+        case CAPTURE_DEVICE_PROBE:
+            AppendCaptureDeviceList(ca_device);
+            break;
+    }
+}