Ios 在20ms以下通过特殊频率创建音频

我想通过选择的频率创建声音。我的代码在23毫秒以上工作，但不低于23毫秒。因为我的RenderTone方法（我在互联网上发现这不是我的代码）每23毫秒调用一次。我如何减少迭代时间？音质可以改变（不要太多） 多谢各位

OSStatus RenderTone(
                void *inRefCon,
                AudioUnitRenderActionFlags  *ioActionFlags,
                const AudioTimeStamp        *inTimeStamp,
                UInt32                      inBusNumber,
                UInt32                      inNumberFrames,
                AudioBufferList             *ioData){
ViewController *viewController =
(__bridge ViewController *)inRefCon;
double theta = viewController->theta;
double theta_increment = 2.0 * M_PI * viewController->frequency / viewController->sampleRate;

// This is a mono tone generator so we only need the first buffer
const int channel = 0;
Float32 *buffer = (Float32 *)ioData->mBuffers[channel].mData;

// Generate the samples
NSLog(@"entered the method");
for (UInt32 frame = 0; frame < inNumberFrames; frame++)
{

    buffer[frame] = sin(theta) * viewController->amp1;

    theta += theta_increment;
    if (theta > 2.0 * M_PI)
    {
        theta -= 2.0 * M_PI;
    }
}

viewController->theta = theta;

return noErr;}


void ToneInterruptionListener(void *inClientData, UInt32 inInterruptionState){
ViewController *viewController =
(__bridge ViewController *)inClientData;

[viewController stop];}

- (void)createToneUnit{
// Configure the search parameters to find the default playback output unit
// (called the kAudioUnitSubType_RemoteIO on iOS but
// kAudioUnitSubType_DefaultOutput on Mac OS X)
AudioComponentDescription defaultOutputDescription;
defaultOutputDescription.componentType = kAudioUnitType_Output;
defaultOutputDescription.componentSubType = kAudioUnitSubType_RemoteIO;
defaultOutputDescription.componentManufacturer = kAudioUnitManufacturer_Apple;
defaultOutputDescription.componentFlags = 0;
defaultOutputDescription.componentFlagsMask = 0;

// Get the default playback output unit
AudioComponent defaultOutput = AudioComponentFindNext(NULL, &defaultOutputDescription);
NSAssert(defaultOutput, @"Can't find default output");

// Create a new unit based on this that we'll use for output
OSErr err = AudioComponentInstanceNew(defaultOutput, &toneUnit);
NSAssert1(toneUnit, @"Error creating unit: %hd", err);

// Set our tone rendering function on the unit
AURenderCallbackStruct input;
input.inputProc = RenderTone;
input.inputProcRefCon = (__bridge void *)(self);
err = AudioUnitSetProperty(toneUnit,
                           kAudioUnitProperty_SetRenderCallback,
                           kAudioUnitScope_Input,
                           0,
                           &input,
                           sizeof(input));
NSAssert1(err == noErr, @"Error setting callback: %hd", err);

// Set the format to 32 bit, single channel, floating point, linear PCM
const int four_bytes_per_float = 4;
const int eight_bits_per_byte = 8;
AudioStreamBasicDescription streamFormat;
streamFormat.mSampleRate = sampleRate;
streamFormat.mFormatID = kAudioFormatLinearPCM;
streamFormat.mFormatFlags =
kAudioFormatFlagsNativeFloatPacked | kAudioFormatFlagIsNonInterleaved;
streamFormat.mBytesPerPacket = four_bytes_per_float;
streamFormat.mFramesPerPacket = 1;
streamFormat.mBytesPerFrame = four_bytes_per_float;
streamFormat.mChannelsPerFrame = 1;
streamFormat.mBitsPerChannel = four_bytes_per_float * eight_bits_per_byte;
err = AudioUnitSetProperty (toneUnit,
                            kAudioUnitProperty_StreamFormat,
                            kAudioUnitScope_Input,
                            0,
                            &streamFormat,
                            sizeof(AudioStreamBasicDescription));
NSAssert1(err == noErr, @"Error setting stream format: %hd", err);}

这里有日志：（23毫秒）

    [[AVAudioSession sharedInstance] setDelegate:self];
[[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryPlayAndRecord error:nil];
[[AVAudioSession sharedInstance] setActive:YES error:nil];


UInt32 audioRouteOverride = kAudioSessionOverrideAudioRoute_None;

AudioSessionSetProperty (
                         kAudioSessionProperty_OverrideAudioRoute,
                         sizeof (audioRouteOverride),
                         &audioRouteOverride
                         );

        [self createToneUnit];
    amp1=0.25;
    // Stop changing parameters on the unit
    OSErr err = AudioUnitInitialize(toneUnit);
    NSAssert1(err == noErr, @"Error initializing unit: %ld", err);

    // Start playback
    err = AudioOutputUnitStart(toneUnit);
    NSAssert1(err == noErr, @"Error starting unit: %ld", err);

2015-05-21 10:26:39.145 CreateBinarySound[223:7676] entered the method
2015-05-21 10:26:39.168 CreateBinarySound[223:7676] entered the method