iPhone microphone输入事件捕获

利用麦克风做为一种事件的输入方式
核心:
通过AudioSession与AudioQueue实现麦克风输入的数据捕捉.

开启AudioSession:
1.    AudioSessionInitialize
2.    AudioSessionSetProperty(kAudioSessionProperty_AudioCategory)
3.    AudioSessionSetActive

建立声音格式:
1.    声音格式的数据结构AudioStreamBasicDescription
2.    使用kAudioFormatLinearPCM来做为声音格式

建立AudioQueue:
1.    AudioQueueNewInput
2.    AudioQueueStart
3.    AudioQueueSetProperty(kAudioQueueProperty_EnableLevelMetering)

获取声音峰值数据:
1.    记录峰值的数据结构AudioQueueLevelMeterState
2.    AudioQueueGetProperty(kAudioQueueProperty_CurrentLevelMeterDB)

关闭AudioQueue:
1.    AudioQueueStop
2.    AudioQueueDispose

代码:

 

 
#import <UIKit/UIKit.h>
#include <AudioToolbox/AudioToolbox.h>
 
@interface MicrophoneTestViewController : UIViewController {
 
    IBOutlet UILabel*    _averagePower;
    IBOutlet UILabel*    _peakPower;
 
    AudioQueueRef                mQueue;
    AudioStreamBasicDescription    mFormat;
    AudioQueueLevelMeterState    *_chan_lvls;
    NSArray                        *_channelNumbers;
}
 
-(void)setChannelNumbers:(NSArray *)v;
-(void)initAudioSession;
 
- (IBAction)startstop: (id) sender;
 
@end
[/code]
 
[code]
#import "MicrophoneTestViewController.h"
 
static void MyInputBufferHandler(void *                                    inUserData,
                                 AudioQueueRef                            inAQ,
                                 AudioQueueBufferRef                    inBuffer,
                                 const AudioTimeStamp *                    inStartTime,
                                 UInt32                                    inNumPackets,
                                 const AudioStreamPacketDescription*    inPacketDesc)
{
    // 如果要记录声音,可以在这里做记录处理.
    // 如果要分析声音数据,可以在这里做记录处理.
}
 
static void interruptionListener(void *    inClientData,
                                 UInt32    inInterruptionState)
{
    // 声音中断通知(BEGIN,END)
}
 
@implementation MicrophoneTestViewController
 
// Implement viewDidLoad to do additional setup after loading the view, typically from a nib.
- (void)viewDidLoad {
    [super viewDidLoad];
 
    _averagePower.text = @"0";
    _peakPower.text = @"0";
    mQueue = NULL;
    _channelNumbers = [[NSArray alloc] initWithObjects:[NSNumber numberWithInt:0], nil];
    _chan_lvls = (AudioQueueLevelMeterState*)malloc(sizeof(AudioQueueLevelMeterState) * [_channelNumbers count]);
 
    [self initAudioSession];
 
    [NSTimer 
     scheduledTimerWithTimeInterval:1.f/30.f
     target:self 
     selector:@selector(_refresh) 
     userInfo:nil 
     repeats:YES
     ];
}
 
- (void)didReceiveMemoryWarning {
    // Releases the view if it doesn't have a superview.
    [super didReceiveMemoryWarning];
 
    // Release any cached data, images, etc that aren't in use.
}
 
- (void)viewDidUnload {
    // Release any retained subviews of the main view.
    // e.g. self.myOutlet = nil;
    [_channelNumbers release];
    free(_chan_lvls);
}
 
 
- (void)dealloc {
    [super dealloc];
}
 
-(void)initAudioSession
{
    OSStatus error = AudioSessionInitialize(NULL, NULL, interruptionListener, self);
    if (error) printf("ERROR INITIALIZING AUDIO SESSION! %d\n", (int)error);
    else 
    {
        UInt32 category = kAudioSessionCategory_PlayAndRecord;    
        error = AudioSessionSetProperty(kAudioSessionProperty_AudioCategory, sizeof(category), &category);
        if (error) printf("couldn't set audio category!");
 
        error = AudioSessionSetActive(true);
        if (error) printf("AudioSessionSetActive (true) failed");
    }
}
 
-(void)setupAudioFormat:(UInt32)inFormatID
{
    memset(&mFormat, 0, sizeof(mFormat));
 
    UInt32 size = sizeof(mFormat.mSampleRate);
    OSStatus result = AudioSessionGetProperty(kAudioSessionProperty_CurrentHardwareSampleRate,
                            &size, 
                            &mFormat.mSampleRate);
 
    size = sizeof(mFormat.mChannelsPerFrame);
    result = AudioSessionGetProperty(kAudioSessionProperty_CurrentHardwareInputNumberChannels, 
                            &size, 
                            &mFormat.mChannelsPerFrame);
 
    mFormat.mFormatID = inFormatID;
    if (inFormatID == kAudioFormatLinearPCM)
    {
        // if we want pcm, default to signed 16-bit little-endian
        mFormat.mFormatFlags = kLinearPCMFormatFlagIsSignedInteger | kLinearPCMFormatFlagIsPacked;
        mFormat.mBitsPerChannel = 16;
        mFormat.mBytesPerPacket = mFormat.mBytesPerFrame = (mFormat.mBitsPerChannel / 8) * mFormat.mChannelsPerFrame;
        mFormat.mFramesPerPacket = 1;
    }
}
 
-(void)startMicrophone
{
    [self setupAudioFormat:kAudioFormatLinearPCM];
    OSStatus result = AudioQueueNewInput(&mFormat, MyInputBufferHandler, NULL, NULL, NULL, 0, &mQueue);
    if (result == noErr) {
        result = AudioQueueStart(mQueue, NULL);
        if (result == noErr) {
            UInt32 val = 1;
            AudioQueueSetProperty(mQueue, kAudioQueueProperty_EnableLevelMetering, &val, sizeof(UInt32));
 
            if (mFormat.mChannelsPerFrame != [_channelNumbers count])
            {
                NSArray *chan_array;
                if (mFormat.mChannelsPerFrame < 2)
                    chan_array = [[NSArray alloc] initWithObjects:[NSNumber numberWithInt:0], nil];
                else
                    chan_array = [[NSArray alloc] initWithObjects:[NSNumber numberWithInt:0], [NSNumber numberWithInt:1], nil];
 
                [self setChannelNumbers:chan_array];
                [chan_array release];
 
                _chan_lvls = (AudioQueueLevelMeterState*)realloc(_chan_lvls, mFormat.mChannelsPerFrame * sizeof(AudioQueueLevelMeterState));
            }
 
            return;
        }
    }
 
    // 失败
    mQueue = NULL;
    NSLog(@"startMicrophone:失败.");
    return;
}
 
-(void)stopMicrophone
{
    if (mQueue) {
        AudioQueueStop(mQueue, true);
        AudioQueueDispose(mQueue, true);
        mQueue = NULL;
    }
}
 
-(void)_refresh
{
    if (mQueue) {
        UInt32 data_sz = sizeof(AudioQueueLevelMeterState) * [_channelNumbers count];
        OSErr status = AudioQueueGetProperty(mQueue, kAudioQueueProperty_CurrentLevelMeterDB, _chan_lvls, &data_sz);
        if (status == noErr)
        {
            // 这里没有去处理多个通道的数据显示,直接就显示最后一个通道的结果了
            // 这里的值就是我们打算用来做为一些触发机制的值了,需要用到的时候直接访问_chan_lvls这个数组
            for (int i=0; i<[_channelNumbers count]; i++)
            {
                NSInteger channelIdx = [(NSNumber *)[_channelNumbers objectAtIndex:i] intValue];
                if (channelIdx < [_channelNumbers count] && channelIdx <= 127)
                {
                    _averagePower.text = [NSString stringWithFormat:@"%f", _chan_lvls[channelIdx].mAveragePower];
                    _peakPower.text = [NSString stringWithFormat:@"%f", _chan_lvls[channelIdx].mPeakPower];
                }
            }
        }
    }
}
 
-(void)setChannelNumbers:(NSArray *)v
{
    [v retain];
    [_channelNumbers release];
    _channelNumbers = v;
}
 
- (IBAction)startstop: (id) sender
{
    if (mQueue) {
        [self stopMicrophone];
    } else {
        [self startMicrophone];
    }
}
 
@end