iOS AudioQueues: глюки в аудио-поплавке

Question

Я записываю поток поплавков, идущих от микрофона (должно быть тишина)

Я установил аудио-очереди с размером буфера 256 поплавков

Типичный буфер выглядит так:

ПАКЕТ 0.004791, 0.012512,0.008423,0.000122, -0,000519, -0,002991, -0.000031,0.001801, -0,000641, 0.001190, -0,003143, -0.001587,0.001587, -0,015503, -0,019440, -0,015167, -0,017670, -0,018158, -0,019928, -0,019409, -0,024017, -0,019684, -0,024719, -0,044128, -0,043579, -0,043152, -0,046417, -0,045380, -0,050079, -0,050262, -0,049164, -0,040710, -0,036713, -0,051056, -0,045868, -0,035034, -0,033722, -0,028534, -0,027161, -0,022186, -0,018036, -0.012207,0.004303, -0,000824, -0.000610,0.014496,0.018005,0.019745,0.019226, 0.016144,0.013184,0.009003,0.014557,0.003357, -0,011353, -0,007751, -0,007660, -0,006409, -0,003357, -0,003510, -0,001038, -0.000092,0.007690,0.002655,0.000000, 0.000000,0.000000,0.000000,0.000000,0.000000,0.000000,0.000000,0.000000, 0.000000,0.000000,0.000000,0.000000,0.000000,0.000000,0.000000,0.000000, 0.000000,0.000000,0.000000,0.000000,0.000000,0.000000,0.000000,0.000000, 0.000000,0.000000,0.000000,0.000000,0.000000,0.000000,0.000000,0.000000, 0.000000,0.000000,0.000000,0.000000,0.000000,0.000000,0.000000,0.000000, 0.000000,0.000000,0.000000,0.000000,0.000000,0.000000,0.000000,0.000000, 0.000000,0.000000,0.000000,0.000000,0.000000,0.000000,0.000000,0.000000, 0.000000,0.000000,0.000000,0.000000,0.000000,0.000000,0.000000,0.000000, 0.000000,0.000000,0.000000, -0,006897, -0.000549,0.003174,0.003540,0.003632, 0.004578,0.005280,0.001831,0.014771,0.014954,0.001801,0.009247,0.011139, 0.005249,0.008087,0.008636,0.007385,0.007263,0.016571,0.020264,0.010590, 0.014801,0.023132,0.027039,0.031128,0.031799,0.037109,0.038757,0.049438, 0.057098,0.042786,0.045593,0.052032,0.045380,0.045227,0.045837,0.043793, 0.041931,0.043976,0.046570,0.030182,0.024475,0.029877,0.026184,0.026001, 0.026611,0.031921,0.035736,0.040710,0.053070,0.042572,0.039917,0.051636, 0.053009,0.053528,0.053009,0.054962,0.055603,0.053833,0.060638,0.050171, 0.041779,0.049194,0.046356,0.000000,0.000000,0.000000,0.000000,0.000000, 0.000000,0.000000,0.000000,0.000000,0.000000,0.000000,0.000000,0.000000, 0.000000,0.000000,0.000000,0.000000,0.000000,0.000000,0.000000,0.000000, 0.000000,0.000000,0.000000,0.000000,0.000000,0.000000,0.000000,0.000000, 0.000000,0.000000,0.000000,0.000000,0.000000,0.000000,0.000000,0.041931, 0.038879,0.034515,0.031494,0.026337,0.034576,0.028992,0.014038,0.018127, 0.017822,0.015137,0.015778,0.013519,0.015564,0.014832,0.023285,0.022034, 0,006317,0.010254,0.010742,0,004303,0,003784, -0,000153, -0,002502, ~

Я не могу понять, почему у меня, кажется, есть случайные группы нулей во входном сигнале. Кажется, что-то прерывистое.

Сначала я подумал, что, возможно, у меня был левый и правый канал, а правый канал всегда записывал ноль. Но, просматривая мой код, я четко настроил его для одного канала.

Тогда я подумал, может быть, это просто места молчания в сигнале. Но это не имеет смысла. Если бы у меня только что была дюжина нулей, то, конечно, 0,000000, я бы ожидал, что последуют очень очень маленькие числа, например, .000007 .000014, но ненулевые числа, кажется, находятся около отметки 0,01.

Я только что попытался переключить свой аудиовход на внешний USB-микрофон, и это улучшает разрешение. Ненулевые числа теперь, кажется, находятся вокруг отметки .001. но все же есть заметный разрыв ...

Интересно, выполняется ли какой-либо расчет на чипе, который округляется до 0. Если это так, можно ли его откалибровать? Что здесь происходит?

Вторая действительно странная проблема, которую я замечаю, это мошеннические ценности.

Вот пример пакета, который содержит некоторые из этих значений (на этот раз с помощью микрофона USB; вы можете увидеть, как улучшается разрешение):

~ ПАКЕТ -0.001343, -0.001190, -0.001526, -0.001373, -0.000946, -0.001526, -0.001221, -0.001190, -0.001221, -0.001251, -0.001373, -0.001190, -0.001312, -0.001312, -0-0.001282, -0.001312, -0.001099, -0.001007, -0.001221, -0.001160, -0.001312, -0.001343, -0.001221, -0.001007, -0.001099, -0.001404, -0.001068, -0.001038, -0.001404, -0.00104038, -0.00104038, -0.00104038, -0.00104038, -0.00104038, -0.001404, -0.001099, -0.001282, -0.001221, -0.001007, -0.001007, -0.001099, -0.001221, -0.001160, -0.001038, -0.001038, -0.001007, -0.000946, -0.001129, -0.000946, -0.000916, -0.000.0000.000946, -0.000946, -0.000824, -0.000824, -0.001007, -0.000763, -0.001038, -0.000854, -0.000977, -0.000916, -0.000641, -0.000977, -0.000916, -0.000946, -0.000732, -0.0008240000, 0,000000,0,000000,0,000000,0,000000,0,000000,0,000000,0,000000, 0,000000,0,000000,0,000000,0,000000,0,000000,0,000000,0,000000,0,000000, 0,000000,0,000000,0,000000,0,000000,0,000000,0,000000,0,000000,0,0000,00,00,0000,000,000000,0,000000,0,000000,0,000000,0,000000,0,000000 0,000000,0,000000,0,000000,0,000000, 0,000000,0,000000,0,000000,0,000000, 0,000000,0,000000,0,000000,0,000000,0,000000,0,000000,0,000000,0,000000, 0,000000,0,000000,0,000000,0,000000,0,000000,0,000000,0,000000,0,000000,00,00,00,00,00,00, 0,000000,0,000000,0,000000, 0,000000,0,000000,0,000000,0,000000,0,000000,0,000000,0,000000,0,000000, 0,000000,0,000000,0,000000,0,000000,0,000000,0,000000,0,000000,0,0000,00,00,00,00,00,0000,00,00,00,00, 0,000000,0,000000, 0,000000,0,000000,0,000000,0,000000,0,000000,0,000000,0,000000,0,000000, 0,000000,0,000000,0,000000,0,000000,0,000000,0,000000,0,000000,0,000000,0,0000,00,00,00,00,00,000000,00,00,00,00000000,0000,00000000,00 чтобы зачитать, 0.000000, -0.000000,2.000000, -2.000000,0.000000, -0.000000,36893488147419103232.000000, -36893488147419103232.000000,0.000000, -0.000000,8589934592.000000, -8589934592.000000,0.000000, -0.000000,158456325028528675187087900672.000000, -158456325028528675187087900672.000000,0.000000, -0.000000,131072.000000, -131072,000000,0.000000, -0.000000,2417851639229258349412352.000000, -2417851639229258349412352.000000,0.000000, -0.000000,562949953421312.000000, -562949953421312.000000,0.000031, -0.000031,10384593717069655257060992658440192.000000, -10384593717069655257060992658440192.000000,0.000000, 0.000000,0.000000,0.000000,0.000000,0.000000,0.000000,0.000000,0.000000,0,000000,0,000000,0,000000,0,000000,0,000000,0,000000,0,000000,0,000000, 0,000000,0,000000,0,000000,0,000000,0,000000,0,000000,0,000000,0,000000, 0,000000,0,000000,0,000000,0,000000,0,000000,0,000000,00,0000,00,00,0000,00,00,000,000000,0,000000,0,000000,0,000000,0,000000,0,000000,0,000000, 0,000000,0,000000,0,000000,0,000000,0,000000,0,000000,0,000000,

Меня это смущает.встречаемость этих глюков низкая;меньше, чем один из 10 кадров.

Означает ли это, что я должен предварительно обработать свой аудиопоток?

В прошлый раз, когда я использовал аудиоустройства, я никогда этого не делал.Я просто передал звук прямо в процедуру определения высоты тона.И с этим проблем не было.Вот мне и интересно, получал ли я там глюки ..

Я получаю глюки как со встроенным микрофоном MacBook, так и с внешним USB-микрофоном

Вот мой код:

//
//  MicRecord.m
//  PitchDetect
//
//  Created by Pi on 05/01/2011.
//

#import "MicRecord.h"

void AudioInputCallback(
                        void * inUserData, 
                        AudioQueueRef inAQ, 
                        AudioQueueBufferRef inBuffer, 
                        const AudioTimeStamp * inStartTime, 
                        UInt32 inNumberPacketDescriptions, 
                        const AudioStreamPacketDescription * inPacketDescs) ;


@implementation MicRecord

@synthesize fftFrame;

/*
- (id) init 
{
    if (self = [super init]) 
    {
        [self setupWithSampleRate: 44100
                          buffers: 12
                           bufLen: 512 ];
    }

    return self;
}
 */

// - - - - - - - -

- (void) setupWithSampleRate: (int) in_sampRate
                     buffers: (int) in_nBuffers
                        step: (int) in_step
                   frameSize: (int) in_frameSize
                      target: (id) in_target
                         sel: (SEL) in_sel
{
    sampRate = in_sampRate;

    nBuffers = in_nBuffers;

    bufLen = in_step;

    frameSize = in_frameSize;

    targ = in_target;
    sel = in_sel;

    audioBuffer = calloc(nBuffers, sizeof(AudioQueueBufferRef *) );
    [self setupAudioFormat];
    [self setupAudioQueue];

    fftFrame = calloc(frameSize, sizeof(float) );
}

// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

- (void) setupAudioFormat
{
    // 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;

    memset(& dataFormat, 
           (int) 0x00, 
           sizeof(dataFormat) );

    dataFormat.mSampleRate = sampRate;
    dataFormat.mFormatID = kAudioFormatLinearPCM;
    dataFormat.mFormatFlags = kAudioFormatFlagsNativeFloatPacked | kAudioFormatFlagIsNonInterleaved;
    dataFormat.mBytesPerPacket = four_bytes_per_float;
    dataFormat.mFramesPerPacket = 1;    
    dataFormat.mBytesPerFrame = four_bytes_per_float;       
    dataFormat.mChannelsPerFrame = 1;   
    dataFormat.mBitsPerChannel = four_bytes_per_float * eight_bits_per_byte;
}

// - - - - - - - - - - - - - - - - -

- (void) setupAudioQueue
{
    currentPacket = 0;

    OSStatus status;

    status = AudioQueueNewInput(& dataFormat,
                                AudioInputCallback,
                                self,
                                CFRunLoopGetCurrent(),
                                kCFRunLoopCommonModes,
                                0,
                                & queue);

    for(int i = 0; i < nBuffers; i++)
    {
        status = AudioQueueAllocateBuffer(queue,
                                          bufLen, 
                                          & audioBuffer[i]);

        status = AudioQueueEnqueueBuffer(queue,
                                         audioBuffer[i], 0, NULL);
    }

    status = AudioQueueFlush (queue);

    printf("Status: %d", (int) status);
}

// - - - - - - - - - - - - - - - - -

- (void) start
{
    OSStatus status = AudioQueueStart(queue, NULL);

    printf("Status: %d", (int) status);
}

// - - - - - - - - - - - - - - -

- (void) stop
{
    AudioQueueStop(queue, true);

    for(int i = 0; i < nBuffers; i++)
        AudioQueueFreeBuffer(queue, audioBuffer[i]);

    AudioQueueDispose(queue, true);
}

// - - - - - - - - - -

- (void) dealloc
{
    [self stop];

    free (audioBuffer);

    [super dealloc];
}


@end

// = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = 

void AudioInputCallback(
                        void                    * inUserData, 
                        AudioQueueRef           inAQ, 
                        AudioQueueBufferRef     inBuffer, 
                        const AudioTimeStamp    * inStartTime, 
                        UInt32                  inNumberPacketDescriptions, 
                        const AudioStreamPacketDescription * inPacketDescs
                        )
{
    MicRecord * x = (MicRecord *) inUserData;

    //if(inNumberPacketDescriptions == 0 && recordState->dataFormat.mBytesPerPacket != 0)
    //{
    //    inNumberPacketDescriptions = inBuffer->mAudioDataByteSize / recordState->dataFormat.mBytesPerPacket;
    //}

    if (0)
        printf("Handling buffer %d\n", (int) x->currentPacket);

    int step = x->bufLen;

    if (inBuffer->mAudioDataBytesCapacity != step)
    {
        printf("---");
    }

    static int k = -1;
    k++;
    static float lastVal = 0;
    static int count = 0;
    if (k < 32) {
        if (k == 0)
            printf("\nfloat buf[32*%d=%d] = {", step, 32*step);
        float * in_buf = (float *) inBuffer->mAudioData;
        printf("\n ~\nPACKET\n");
        for (int i = 0; i < step; i++)
        {
            /*
            if (fabs(in_buf[i]) < .0001 && fabs(lastVal) > .0001)
            {
                printf("%d Nonzeros\n",count);
                count = 0;
            }
            if (fabs(in_buf[i]) > .0001 && fabs(lastVal) < .0001)
            {
                printf("%d Zeros\n",count);
                count = 0;
            }
            count++;
            lastVal = in_buf[i];*/
            printf("%f,", in_buf[i] );

            if (i % 8 == 0)
                printf("\n");
            //if (count % (8 * 64) == 0)
            //  printf("\n");

            count++;
        }
        if (k == 31)
            printf("}\n");
    }


    // shifty frame data down by 'step' elements 
    // to make room for new data
    // imagine cutting out elts [0] thru [step-1] (ie 'step' of them)
    // first new elt at pos [0] will be [step]
    memmove(& x->fftFrame[0], // dest first
            & x->fftFrame[step], // src
            x->frameSize - step
            );

    memcpy(& x->fftFrame[x->frameSize - step],
           inBuffer->mAudioData,
           step * sizeof(float)
           );

    x->currentPacket += inNumberPacketDescriptions;
    // }

    AudioQueueEnqueueBuffer(x->queue, inBuffer, 0, NULL);

    [x->targ performSelector: x->sel];
}

Answer 1

Моим первым предложением было бы вывести любые printf из обратного вызова самого низкого уровня. Если они медленные, вполне возможно, что вы пропустили буфер здесь или там. Я не знаю, будут ли они отображаться в виде блоков нулей или ложных образцов, которые вы наблюдаете, но это может произойти.

Что произойдет с вашей очередью, если вы заполните ее быстрее, чем опустошите?