iOS 音频采集

采集方式

• 音频采集可以参考上次的视频采集方式，在里面添加相应的音频采集即可，只不过可定制型不强。(视频采集)
• 使用audioUnit，可定制型强，本文主要介绍这种方式。

实现方式

详细介绍参考（iOS 音频AudioComponentDescription类型设置）

 AudioComponentDescription acd;
    acd.componentType = kAudioUnitType_Output;//类型输出
    //acd.componentSubType = kAudioUnitSubType_VoiceProcessingIO;//
    acd.componentSubType = kAudioUnitSubType_RemoteIO;//
    acd.componentManufacturer = kAudioUnitManufacturer_Apple;//ios固定这么写，mac不同
    acd.componentFlags = 0;
    acd.componentFlagsMask = 0;
    //用来描述音频组件
    AudioComponent component = AudioComponentFindNext(NULL, &acd);
    
    //用来表示特定音频组件的实例
    AudioComponentInstance componetInstance;
    OSStatus status = noErr;
    //创建实例
    status = AudioComponentInstanceNew(component, &componetInstance);
    
    UInt32 flagOne = 1;
    //打开IO，1 是麦克风，0 是扬声器
    AudioUnitSetProperty(componetInstance, kAudioOutputUnitProperty_EnableIO, kAudioUnitScope_Input, 1, &flagOne, sizeof(flagOne));

设置输出音频属性

    AudioStreamBasicDescription desc = {0};
    desc.mSampleRate = 44100;//采样率
    desc.mFormatID = kAudioFormatLinearPCM;//类型交错存储PCM
    desc.mFormatFlags = kAudioFormatFlagIsSignedInteger | kAudioFormatFlagsNativeEndian | kAudioFormatFlagIsPacked;
    desc.mChannelsPerFrame = 2;//声道数
    desc.mFramesPerPacket = 1;// 非压缩数据，固定填1
    desc.mBitsPerChannel = 16;//每声道占的位数
    desc.mBytesPerFrame = desc.mBitsPerChannel / 8 * desc.mChannelsPerFrame;
    desc.mBytesPerPacket = desc.mBytesPerFrame * desc.mFramesPerPacket;

设置采集回调

    AURenderCallbackStruct cb;//采集回调
    cb.inputProcRefCon = (__bridge  void *)(self);
    cb.inputProc = handleInputBuffer;
    status = AudioUnitSetProperty(componetInstance, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Output, 1, &desc, sizeof(desc));//设置流格式
    status = AudioUnitSetProperty(componetInstance, kAudioOutputUnitProperty_SetInputCallback, kAudioUnitScope_Global, 1, &cb, sizeof(cb));//设置回调

初始化

  AVAudioSession *session = [AVAudioSession sharedInstance];

    NSError *error;
    //设置采样率
    [session setPreferredSampleRate:44100 error:&error];
    
    //设置类型
    [session setCategory:AVAudioSessionCategoryPlayAndRecord withOptions:AVAudioSessionCategoryOptionDefaultToSpeaker | AVAudioSessionCategoryOptionInterruptSpokenAudioAndMixWithOthers error:&error];
    
    //
    [session setActive:YES withOptions:kAudioSessionSetActiveFlag_NotifyOthersOnDeactivation error:&error];
    [session setActive:YES error:&error];
    
    //创建一个线程
    taskQueue = dispatch_queue_create("com.mt.audioCapture", NULL);

开始采集

- (void)startRecord{
    dispatch_async(taskQueue, ^{
        NSLog(@"开始录音");
        //每次设置一下状态，防止别的地方被修改或者出现其他情况
        [[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryPlayAndRecord withOptions:AVAudioSessionCategoryOptionDefaultToSpeaker | AVAudioSessionCategoryOptionInterruptSpokenAudioAndMixWithOthers error:nil];
        AudioOutputUnitStart(self->componetInstance);
    });
}

结束采集

- (void)endRecord{
    dispatch_async(taskQueue, ^{
        NSLog(@"停止录音");
        AudioOutputUnitStop(self->componetInstance);
    });
}

采集的回调，数据获取

static OSStatus handleInputBuffer(void *inRefCon,
                                  AudioUnitRenderActionFlags *ioActionFlags,
                                  const AudioTimeStamp *inTimeStamp,
                                  UInt32 inBusNumber,
                                  UInt32 inNumberFrames,
                                  AudioBufferList *ioData) {
    @autoreleasepool {
        Test *source = (__bridge Test *)inRefCon;
        
        if (!source) {
            return -1;
        }
        
        AudioBuffer buffer;
        buffer.mData = NULL;
        buffer.mDataByteSize = 0;
        buffer.mNumberChannels = 1;
        
        AudioBufferList bufferList;
        bufferList.mNumberBuffers = 1;
        bufferList.mBuffers[0] = buffer;
        
        static int64_t get_audio_base_timesss = 0;
        Float64 currentTime = CMTimeGetSeconds(CMClockMakeHostTimeFromSystemUnits(inTimeStamp->mHostTime));
        if (get_audio_base_timesss == 0) {
            get_audio_base_timesss = currentTime;
        }
        int64_t pts = (int64_t)((currentTime - get_audio_base_timesss) * 1000);
        
        ///获取数据
        OSStatus status = AudioUnitRender(source->componetInstance,
                                          ioActionFlags,
                                          inTimeStamp,
                                          inBusNumber,
                                          inNumberFrames,
                                          &bufferList);
        
        if ((NO)/*静音*/) {
            for (int i = 0; i < bufferList.mNumberBuffers; i++) {
                AudioBuffer ab = bufferList.mBuffers[i];
                memset(ab.mData, 0, ab.mDataByteSize);
            }
        }
        
        if (status == noErr) {
            //            //音频数据
            //            bufferList.mBuffers[0].mData
            //            //音频长度
            //            bufferList.mBuffers[0].mDataByteSize
            //            //pts
            //            pts
            //            //转为NSData
            //            [NSData dataWithBytes:bufferList.mBuffers[0].mData length:bufferList.mBuffers[0].mDataByteSize]
        }
        /*如果有分离左右声道需求的话
         //            NSData *data = [NSData dataWithBytes:buffers.mBuffers[0].mData length:buffers.mBuffers[0].mDataByteSize];
         //
         //               NSMutableData *leftData = [NSMutableData dataWithCapacity:0];
         //               NSMutableData *rightData = [NSMutableData dataWithCapacity:0];
         //            // 分离左右声道
         //             for (int i = 0; i < data.length; i+=4) {
         //                 [leftData appendData:[data subdataWithRange:NSMakeRange(i, 2)]];
         //                 [rightData appendData:[data subdataWithRange:NSMakeRange(i+2, 2)]];
         //             }
         */
        return noErr;
    }
}

Demo地址整理后奉上。
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