Naive recording of 16384 frames of the Remote IO input

RecordRemoteIO.m

//
//  RecordRemoteIO.m
//  AudioTest
//
//  Created by Mark Stultz on 5/5/15.
//  Copyright (c) 2015 Mark Stultz. All rights reserved.
//

#import <AudioToolbox/AudioToolbox.h>
#import "RecordRemoteIO.h"

#define kOutputBus 0
#define kInputBus 1

@interface RecordRemoteIO ()
{
@public
    AUGraph m_graph;
    AUNode m_nodeRemoteIO;
    AudioUnit m_unitRemoteIO;
    uint8_t *m_buffer;
    ExtAudioFileRef m_file;
    UInt32 m_frames;
}

@end

OSStatus OnRenderNotify(void *inRefCon, AudioUnitRenderActionFlags *ioActionFlags, const AudioTimeStamp *inTimeStamp, UInt32 inBusNumber, UInt32 inNumberFrames, AudioBufferList *ioData)
{
    AudioEngine *engine = (__bridge AudioEngine *)inRefCon;
    
    AudioBufferList bufferList;
    
    // redundant
    bufferList.mNumberBuffers = 1;
    bufferList.mBuffers[0].mData = engine->m_buffer;
    bufferList.mBuffers[0].mDataByteSize = 2 * inNumberFrames;
    bufferList.mBuffers[0].mNumberChannels = 1;
    
    ioData = &bufferList;
    
    OSStatus status = AudioUnitRender(engine->m_unitRemoteIO, ioActionFlags, inTimeStamp, 1, inNumberFrames, ioData);
    if (status != noErr) {
        printf("AudioUnitRender error: %d\n", status);
        return status;
    }
    
    // the sample buffer now contains samples you can work with
    
    if (engine->m_file) {
        OSStatus status = ExtAudioFileWrite(engine->m_file, inNumberFrames, ioData);
        if (status != noErr) {
            printf("ExtAudioFileWrite error: %d\n", status);
            return status;
        }
        
        engine->m_frames += inNumberFrames;
        if (engine->m_frames > 4096 * 4) {
            OSStatus status = ExtAudioFileDispose(engine->m_file);
            if (status != noErr) {
                printf("ExtAudioFileDispose error: %d\n", status);
                return status;
            }
            
            engine->m_file = nil;
        }
    }
    
    return noErr;
}

@implementation AudioEngine

- (instancetype)init
{
    self = [super init];
    if (self != nil) {
        m_buffer = malloc(4 * 1024);
        m_frames = 0;
        
        // 1. Create graph
        {
            OSStatus status = NewAUGraph(&m_graph);
            if (status != noErr) {
                NSLog(@"NewAUGraph failed: %d", status);
                return nil;
            }
            
            status = AUGraphOpen(m_graph);
            if (status != noErr) {
                NSLog(@"NewAUGraph failed: %d", status);
                return nil;
            }
        }
        
        // 2. Create, add, and configure RemoteIO
        {
            AudioComponentDescription description;
            memset(&description, 0, sizeof(AudioComponentDescription));
            description.componentType = kAudioUnitType_Output;
            description.componentSubType = kAudioUnitSubType_RemoteIO;
            description.componentManufacturer = kAudioUnitManufacturer_Apple;

            OSStatus status = AUGraphAddNode(m_graph, &description, &m_nodeRemoteIO);
            if (status != noErr) {
                NSLog(@"AUGraphAddNode failed: %d", status);
                return nil;
            }
            
            status = AUGraphNodeInfo(m_graph, m_nodeRemoteIO, &description, &m_unitRemoteIO);
            if (status != noErr) {
                NSLog(@"AUGraphNodeInfo failed: %d", status);
                return nil;
            }
            
            // Enable IO
            UInt32 enableIO = 1;
            UInt32 size = sizeof(UInt32);
            status = AudioUnitSetProperty(m_unitRemoteIO, kAudioOutputUnitProperty_EnableIO, kAudioUnitScope_Input, kInputBus, &enableIO, size);
            if (status != noErr) {
                NSLog(@"AudioUnitSetProperty failed: %d", status);
                return nil;
            }
            
            status = AudioUnitGetProperty(m_unitRemoteIO, kAudioOutputUnitProperty_EnableIO, kAudioUnitScope_Input, kInputBus, &enableIO, &size);
            if (status != noErr) {
                NSLog(@"AudioUnitGetProperty failed: %d", status);
                return nil;
            }
            
            // Configure format
            AudioStreamBasicDescription format;
            format.mSampleRate = 44100.00;
            format.mFormatID = kAudioFormatLinearPCM;
            format.mFormatFlags = kAudioFormatFlagIsSignedInteger | kAudioFormatFlagIsPacked;
            format.mFramesPerPacket = 1;
            format.mChannelsPerFrame = 1;
            format.mBitsPerChannel = 16;
            format.mBytesPerPacket = 2;
            format.mBytesPerFrame = 2;
            
            status = AudioUnitSetProperty(m_unitRemoteIO, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Output, kInputBus, &format, sizeof(AudioStreamBasicDescription));
            if (status != noErr) {
                NSLog(@"AudioUnitSetProperty failed: %d", status);
                return nil;
            }
            
            status = AudioUnitSetProperty(m_unitRemoteIO, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Input, kOutputBus, &format, sizeof(AudioStreamBasicDescription));
            if (status != noErr) {
                NSLog(@"AudioUnitSetProperty failed: %d", status);
                return nil;
            }
            
            // Add callback
            AURenderCallbackStruct callback;
            callback.inputProc = OnRenderNotify;
            callback.inputProcRefCon = (__bridge void *)(self);
            status = AudioUnitSetProperty(m_unitRemoteIO, kAudioOutputUnitProperty_SetInputCallback, kAudioUnitScope_Global, kInputBus, &callback, sizeof(AURenderCallbackStruct));
            if (status != noErr) {
                NSLog(@"AudioUnitSetProperty failed: %d", status);
                return nil;
            }
        }
        
        // 3. Start it up
        {
            OSStatus status = AUGraphInitialize(m_graph);
            if (status != noErr) {
                switch (status) {
                    case kAUGraphErr_NodeNotFound:
                    case kAUGraphErr_InvalidConnection:
                    case kAUGraphErr_OutputNodeErr:
                    case kAUGraphErr_CannotDoInCurrentContext:
                    case kAUGraphErr_InvalidAudioUnit:
                        break;
                }
                
                NSLog(@"AUGraphInitialize failed: %d", status);
                return nil;
            }

            status = AUGraphStart(m_graph);
            if (status != noErr) {
                NSLog(@"AUGraphInitialize failed: %d", status);
                return nil;
            }
        }
        
        // 4. Create file
        {
            AudioStreamBasicDescription format;
            format.mSampleRate = 44100.00;
            format.mFormatID = kAudioFormatLinearPCM;
            format.mFormatFlags = kAudioFormatFlagIsSignedInteger | kAudioFormatFlagIsPacked;
            format.mFramesPerPacket = 1;
            format.mChannelsPerFrame = 1;
            format.mBitsPerChannel = 16;
            format.mBytesPerPacket = 2;
            format.mBytesPerFrame = 2;
            
            NSURL *URL = [NSURL URLWithString:[NSTemporaryDirectory() stringByAppendingPathComponent:@"mic.wav"]];
            NSLog(@"%@", URL.path);
            
            OSStatus status = ExtAudioFileCreateWithURL((__bridge CFURLRef)(URL), kAudioFileWAVEType, &format, 0, kAudioFileFlags_EraseFile, &m_file);
            if (status != noErr) {
                NSLog(@"AUGraphInitialize failed: %d", status);
                return nil;
            }
        }
        
        CAShow(m_graph);
    }
    
    return self;
}

@end