iOS AudioQueue实时录音

在iOS中，AVCaptureSession、AudioUnit、AudioQueue均可以实现实时录制音频。
其中，AVCaptureSession采集出来的PCM采样率默认为44100Hz，如果想要自定义采样率又不想重采样的话，可以使用AudioUnit和AudioQueue实现。

比如我需要采集编码8k16位的G711，那么采集时就需要设置8000Hz的采样率

code如下：

#import 

@protocol AQCaptureDelegate 
- (void)returnData:(NSMutableData *)data;
@end

@interface AQCapture : NSObject
@property (nonatomic,strong) iddelegate;
- (void)startRecord;
- (void)stopRecord;
@end

#import "AQCapture.h"
#import 
#import 

#define QUEUE_BUFFER_SIZE 3      //输出音频队列缓冲个数
#define kDefaultBufferDurationSeconds 0.06      //调整这个值使得录音的缓冲区大小为960,实际会小于或等于960,需要处理小于960的情况
#define kDefaultSampleRate 8000      //定义采样率为8000

static BOOL isRecording = NO;

@interface AQCapture(){
    AudioQueueRef _audioQueue;      //输出音频播放队列
    AudioStreamBasicDescription _recordFormat;
    AudioQueueBufferRef _audioBuffers[QUEUE_BUFFER_SIZE];      //输出音频缓存
}
@property (nonatomic, assign) BOOL isRecording;
@end

@implementation AQCapture

- (instancetype)init
{
    self = [super init];
    if (self) {
        [[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryPlayAndRecord error:nil];//PlayAndRecord
        [[AVAudioSession sharedInstance] setActive:YES error:nil];//如果录音时同时需要播放媒体，那么必须加上这两行代码
        memset(&_recordFormat, 0, sizeof(_recordFormat));
        _recordFormat.mSampleRate = kDefaultSampleRate;
        _recordFormat.mChannelsPerFrame = 1;
        _recordFormat.mFormatID = kAudioFormatLinearPCM;
        _recordFormat.mFormatFlags = kLinearPCMFormatFlagIsSignedInteger | kLinearPCMFormatFlagIsPacked;
        _recordFormat.mBitsPerChannel = 16;
        _recordFormat.mBytesPerPacket = _recordFormat.mBytesPerFrame = (_recordFormat.mBitsPerChannel / 8) * _recordFormat.mChannelsPerFrame;
        _recordFormat.mFramesPerPacket = 1;
        //初始化音频输入队列
        AudioQueueNewInput(&_recordFormat, inputBufferHandler, (__bridge void *)(self), NULL, NULL, 0, &_audioQueue);
        //计算估算的缓存区大小
        int frames = (int)ceil(kDefaultBufferDurationSeconds * _recordFormat.mSampleRate);
        int bufferByteSize = frames * _recordFormat.mBytesPerFrame;
        //        NSLog(@"缓存区大小%d",bufferByteSize);
        //创建缓冲器
        for (int i = 0; i < QUEUE_BUFFER_SIZE; i++){
            AudioQueueAllocateBuffer(_audioQueue, bufferByteSize, &_audioBuffers[i]);
            AudioQueueEnqueueBuffer(_audioQueue, _audioBuffers[i], 0, NULL);
        }
    }
    return self;
}

void inputBufferHandler(void *inUserData, AudioQueueRef inAQ, AudioQueueBufferRef inBuffer, const AudioTimeStamp *inStartTime,UInt32 inNumPackets, const AudioStreamPacketDescription *inPacketDesc)
{
    if (inNumPackets > 0) {
        AQCapture *recorder = (__bridge AQCapture*)inUserData;
        [recorder processAudioBuffer:inBuffer withQueue:inAQ];
    }
    if (isRecording) {
        AudioQueueEnqueueBuffer(inAQ, inBuffer, 0, NULL);
    }
}

- (void)processAudioBuffer:(AudioQueueBufferRef)audioQueueBufferRef withQueue:(AudioQueueRef)audioQueueRef
{
    NSMutableData *data = [NSMutableData dataWithBytes:audioQueueBufferRef->mAudioData length:audioQueueBufferRef->mAudioDataByteSize];
    if (data.length < 960) { //处理长度小于960的情况,此处是补00
        Byte byte[] = {0x00};
        NSData *zeroData = [[NSData alloc] initWithBytes:byte length:1];
        for (NSUInteger i = data.length; i < 960; i++) {
            [data appendData:zeroData];
        }
    }
//    NSLog(@"%@",data);
    [self.delegate returnData:data];
}

- (void)startRecord
{
    // 开始录音
    AudioQueueStart(_audioQueue, NULL);
    isRecording = YES;
}

- (void)stopRecord
{
    if (isRecording)
    {
        isRecording = NO;
        //停止录音队列和移除缓冲区,以及关闭session，这里无需考虑成功与否
        AudioQueueStop(_audioQueue, true);
        //移除缓冲区,true代表立即结束录制，false代表将缓冲区处理完再结束
        AudioQueueDispose(_audioQueue, true);
    }
//    NSLog(@"停止录制");
}

- (void)dealloc {
    _audioQueue = nil;
}


@end