shithub: aacenc

ref: a0be8d87f3c4d762ddcfbe587096fe832356c0f9
dir: /libfaac/tns.c/

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/*
 * FAAC - Freeware Advanced Audio Coder
 * Copyright (C) 2001 Menno Bakker
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.

 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * $Id: tns.c,v 1.8 2001/06/08 18:01:09 menno Exp $
 */

#include <math.h>
#include "frame.h"
#include "coder.h"
#include "bitstream.h"
#include "tns.h"
#include "util.h"

/***********************************************/
/* TNS Profile/Frequency Dependent Parameters  */
/***********************************************/
static unsigned long tnsSupportedSamplingRates[13] =
{ 96000,88200,64000,48000,44100,32000,24000,22050,16000,12000,11025,8000,0 };

/* Limit bands to > 2.0 kHz */
static unsigned short tnsMinBandNumberLong[12] =
{ 11, 12, 15, 16, 17, 20, 25, 26, 24, 28, 30, 31 };
static unsigned short tnsMinBandNumberShort[12] =
{ 2, 2, 2, 3, 3, 4, 6, 6, 8, 10, 10, 12 };

/**************************************/
/* Main/Low Profile TNS Parameters    */
/**************************************/
static unsigned short tnsMaxBandsLongMainLow[12] =
{ 31, 31, 34, 40, 42, 51, 46, 46, 42, 42, 42, 39 };

static unsigned short tnsMaxBandsShortMainLow[12] =
{ 9, 9, 10, 14, 14, 14, 14, 14, 14, 14, 14, 14 };

static unsigned short tnsMaxOrderLongMain = 20;
static unsigned short tnsMaxOrderLongLow = 12;
static unsigned short tnsMaxOrderShortMainLow = 7;


/*****************************************************/
/* InitTns:                                          */
/*****************************************************/
void TnsInit(faacEncHandle hEncoder)
{
    unsigned int channel;
    int fsIndex = hEncoder->sampleRateIdx;
    int profile = hEncoder->config.aacObjectType;

    for (channel = 0; channel < hEncoder->numChannels; channel++) {
        TnsInfo *tnsInfo = &hEncoder->coderInfo[channel].tnsInfo;

        switch( profile ) {
        case MAIN:
        case LTP:
            tnsInfo->tnsMaxBandsLong = tnsMaxBandsLongMainLow[fsIndex];
            tnsInfo->tnsMaxBandsShort = tnsMaxBandsShortMainLow[fsIndex];
            if (hEncoder->config.mpegVersion == 1) { /* MPEG2 */
                tnsInfo->tnsMaxOrderLong = tnsMaxOrderLongMain;
            } else { /* MPEG4 */
                if (fsIndex <= 5) /* fs > 32000Hz */
                    tnsInfo->tnsMaxOrderLong = 12;
                else
                    tnsInfo->tnsMaxOrderLong = 20;
            }
            tnsInfo->tnsMaxOrderShort = tnsMaxOrderShortMainLow;
            break;
        case LOW :
            tnsInfo->tnsMaxBandsLong = tnsMaxBandsLongMainLow[fsIndex];
            tnsInfo->tnsMaxBandsShort = tnsMaxBandsShortMainLow[fsIndex];
            if (hEncoder->config.mpegVersion == 1) { /* MPEG2 */
                tnsInfo->tnsMaxOrderLong = tnsMaxOrderLongLow;
            } else { /* MPEG4 */
                if (fsIndex <= 5) /* fs > 32000Hz */
                    tnsInfo->tnsMaxOrderLong = 12;
                else
                    tnsInfo->tnsMaxOrderLong = 20;
            }
            tnsInfo->tnsMaxOrderShort = tnsMaxOrderShortMainLow;
            break;
        }
        tnsInfo->tnsMinBandNumberLong = tnsMinBandNumberLong[fsIndex];
        tnsInfo->tnsMinBandNumberShort = tnsMinBandNumberShort[fsIndex];
    }
}


/*****************************************************/
/* TnsEncode:                                        */
/*****************************************************/
void TnsEncode(TnsInfo* tnsInfo,       /* TNS info */
               int numberOfBands,       /* Number of bands per window */
               int maxSfb,              /* max_sfb */
               enum WINDOW_TYPE blockType,   /* block type */
               int* sfbOffsetTable,     /* Scalefactor band offset table */
               double* spec)            /* Spectral data array */
{
    int numberOfWindows,windowSize;
    int startBand,stopBand,order;    /* Bands over which to apply TNS */
    int lengthInBands;               /* Length to filter, in bands */
    int w;
    int startIndex,length;
    double gain;

    switch( blockType ) {
    case ONLY_SHORT_WINDOW :

        /* TNS not used for short blocks currently */
        tnsInfo->tnsDataPresent = 0;
        return;

        numberOfWindows = MAX_SHORT_WINDOWS;
        windowSize = BLOCK_LEN_SHORT;
        startBand = tnsInfo->tnsMinBandNumberShort;
        stopBand = numberOfBands;
        lengthInBands = stopBand-startBand;
        order = tnsInfo->tnsMaxOrderShort;
        startBand = min(startBand,tnsInfo->tnsMaxBandsShort);
        stopBand = min(stopBand,tnsInfo->tnsMaxBandsShort);
        break;

    default:
        numberOfWindows = 1;
        windowSize = BLOCK_LEN_SHORT;
        startBand = tnsInfo->tnsMinBandNumberLong;
        stopBand = numberOfBands;
        lengthInBands = stopBand - startBand;
        order = tnsInfo->tnsMaxOrderLong;
        startBand = min(startBand,tnsInfo->tnsMaxBandsLong);
        stopBand = min(stopBand,tnsInfo->tnsMaxBandsLong);
        break;
    }

    /* Make sure that start and stop bands < maxSfb */
    /* Make sure that start and stop bands >= 0 */
    startBand = min(startBand,maxSfb);
    stopBand = min(stopBand,maxSfb);
    startBand = max(startBand,0);
    stopBand = max(stopBand,0);

    tnsInfo->tnsDataPresent = 0;     /* default TNS not used */

    /* Perform analysis and filtering for each window */
    for (w=0;w<numberOfWindows;w++) {

        TnsWindowData* windowData = &tnsInfo->windowData[w];
        TnsFilterData* tnsFilter = windowData->tnsFilter;
        double* k = tnsFilter->kCoeffs;    /* reflection coeffs */
        double* a = tnsFilter->aCoeffs;    /* prediction coeffs */

        windowData->numFilters=0;
        windowData->coefResolution = DEF_TNS_COEFF_RES;
        startIndex = w * windowSize + sfbOffsetTable[startBand];
        length = sfbOffsetTable[stopBand] - sfbOffsetTable[startBand];
        gain = LevinsonDurbin(order,length,&spec[startIndex],k);

        if (gain>DEF_TNS_GAIN_THRESH) {  /* Use TNS */
            int truncatedOrder;
            windowData->numFilters++;
            tnsInfo->tnsDataPresent=1;
            tnsFilter->direction = 0;
            tnsFilter->coefCompress = 0;
            tnsFilter->length = lengthInBands;
            QuantizeReflectionCoeffs(order,DEF_TNS_COEFF_RES,k,tnsFilter->index);
            truncatedOrder = TruncateCoeffs(order,DEF_TNS_COEFF_THRESH,k);
            tnsFilter->order = truncatedOrder;
            StepUp(truncatedOrder,k,a);    /* Compute predictor coefficients */
            TnsInvFilter(length,&spec[startIndex],tnsFilter);      /* Filter */
        }
    }
}


/*****************************************************/
/* TnsEncodeFilterOnly:                              */
/* This is a stripped-down version of TnsEncode()    */
/* which performs TNS analysis filtering only        */
/*****************************************************/
void TnsEncodeFilterOnly(TnsInfo* tnsInfo,           /* TNS info */
                         int numberOfBands,          /* Number of bands per window */
                         int maxSfb,                 /* max_sfb */
                         enum WINDOW_TYPE blockType, /* block type */
                         int* sfbOffsetTable,        /* Scalefactor band offset table */
                         double* spec)               /* Spectral data array */
{
    int numberOfWindows,windowSize;
    int startBand,stopBand;    /* Bands over which to apply TNS */
    int w;
    int startIndex,length;

    switch( blockType ) {
    case ONLY_SHORT_WINDOW :
        numberOfWindows = MAX_SHORT_WINDOWS;
        windowSize = BLOCK_LEN_SHORT;
        startBand = tnsInfo->tnsMinBandNumberShort;
        stopBand = numberOfBands;
        startBand = min(startBand,tnsInfo->tnsMaxBandsShort);
        stopBand = min(stopBand,tnsInfo->tnsMaxBandsShort);
        break;

    default:
        numberOfWindows = 1;
        windowSize = BLOCK_LEN_LONG;
        startBand = tnsInfo->tnsMinBandNumberLong;
        stopBand = numberOfBands;
        startBand = min(startBand,tnsInfo->tnsMaxBandsLong);
        stopBand = min(stopBand,tnsInfo->tnsMaxBandsLong);
        break;
    }

    /* Make sure that start and stop bands < maxSfb */
    /* Make sure that start and stop bands >= 0 */
    startBand = min(startBand,maxSfb);
    stopBand = min(stopBand,maxSfb);
    startBand = max(startBand,0);
    stopBand = max(stopBand,0);


    /* Perform filtering for each window */
    for(w=0;w<numberOfWindows;w++)
    {
        TnsWindowData* windowData = &tnsInfo->windowData[w];
        TnsFilterData* tnsFilter = windowData->tnsFilter;

        startIndex = w * windowSize + sfbOffsetTable[startBand];
        length = sfbOffsetTable[stopBand] - sfbOffsetTable[startBand];

        if (tnsInfo->tnsDataPresent  &&  windowData->numFilters) {  /* Use TNS */
            TnsInvFilter(length,&spec[startIndex],tnsFilter);
        }
    }
}


/*****************************************************/
/* TnsDecodeFilterOnly:                              */
/* This is a stripped-down version of TnsEncode()    */
/* which performs TNS synthesis filtering only       */
/*****************************************************/
void TnsDecodeFilterOnly(TnsInfo* tnsInfo,           /* TNS info */
                         int numberOfBands,          /* Number of bands per window */
                         int maxSfb,                 /* max_sfb */
                         enum WINDOW_TYPE blockType, /* block type */
                         int* sfbOffsetTable,        /* Scalefactor band offset table */
                         double* spec)               /* Spectral data array */
{
    int numberOfWindows,windowSize;
    int startBand,stopBand;    /* Bands over which to apply TNS */
    int w;
    int startIndex,length;

    switch( blockType ) {
    case ONLY_SHORT_WINDOW :
        numberOfWindows = MAX_SHORT_WINDOWS;
        windowSize = BLOCK_LEN_SHORT;
        startBand = tnsInfo->tnsMinBandNumberShort;
        stopBand = numberOfBands;
        startBand = min(startBand,tnsInfo->tnsMaxBandsShort);
        stopBand = min(stopBand,tnsInfo->tnsMaxBandsShort);
        break;

    default:
        numberOfWindows = 1;
        windowSize = BLOCK_LEN_LONG;
        startBand = tnsInfo->tnsMinBandNumberLong;
        stopBand = numberOfBands;
        startBand = min(startBand,tnsInfo->tnsMaxBandsLong);
        stopBand = min(stopBand,tnsInfo->tnsMaxBandsLong);
        break;
    }

    /* Make sure that start and stop bands < maxSfb */
    /* Make sure that start and stop bands >= 0 */
    startBand = min(startBand,maxSfb);
    stopBand = min(stopBand,maxSfb);
    startBand = max(startBand,0);
    stopBand = max(stopBand,0);


    /* Perform filtering for each window */
    for(w=0;w<numberOfWindows;w++)
    {
        TnsWindowData* windowData = &tnsInfo->windowData[w];
        TnsFilterData* tnsFilter = windowData->tnsFilter;

        startIndex = w * windowSize + sfbOffsetTable[startBand];
        length = sfbOffsetTable[stopBand] - sfbOffsetTable[startBand];

        if (tnsInfo->tnsDataPresent  &&  windowData->numFilters) {  /* Use TNS */
            TnsFilter(length,&spec[startIndex],tnsFilter);
        }
    }
}


/*****************************************************/
/* TnsFilter:                                        */
/*   Filter the given spec with specified length     */
/*   using the coefficients specified in filter.     */
/*   Not that the order and direction are specified  */
/*   withing the TNS_FILTER_DATA structure.          */
/*****************************************************/
static void TnsFilter(int length,double* spec,TnsFilterData* filter)
{
    int i,j,k=0;
    int order=filter->order;
    double* a=filter->aCoeffs;

    /* Determine loop parameters for given direction */
    if (filter->direction) {

        /* Startup, initial state is zero */
        for (i=length-2;i>(length-1-order);i--) {
            k++;
            for (j=1;j<=k;j++) {
                spec[i]-=spec[i+j]*a[j];
            }
        }

        /* Now filter completely inplace */
        for (i=length-1-order;i>=0;i--) {
            for (j=1;j<=order;j++) {
                spec[i]-=spec[i+j]*a[j];
            }
        }


    } else {

        /* Startup, initial state is zero */
        for (i=1;i<order;i++) {
            for (j=1;j<=i;j++) {
                spec[i]-=spec[i-j]*a[j];
            }
        }

        /* Now filter completely inplace */
        for (i=order;i<length;i++) {
            for (j=1;j<=order;j++) {
                spec[i]-=spec[i-j]*a[j];
            }
        }
    }
}


/********************************************************/
/* TnsInvFilter:                                        */
/*   Inverse filter the given spec with specified       */
/*   length using the coefficients specified in filter. */
/*   Not that the order and direction are specified     */
/*   withing the TNS_FILTER_DATA structure.             */
/********************************************************/
static void TnsInvFilter(int length,double* spec,TnsFilterData* filter)
{
    int i,j,k=0;
    int order=filter->order;
    double* a=filter->aCoeffs;
    double* temp;

    temp = (double *)AllocMemory(length * sizeof (double));

    /* Determine loop parameters for given direction */
    if (filter->direction) {

        /* Startup, initial state is zero */
        temp[length-1]=spec[length-1];
        for (i=length-2;i>(length-1-order);i--) {
            temp[i]=spec[i];
            k++;
            for (j=1;j<=k;j++) {
                spec[i]+=temp[i+j]*a[j];
            }
        }

        /* Now filter the rest */
        for (i=length-1-order;i>=0;i--) {
            temp[i]=spec[i];
            for (j=1;j<=order;j++) {
                spec[i]+=temp[i+j]*a[j];
            }
        }


    } else {

        /* Startup, initial state is zero */
        temp[0]=spec[0];
        for (i=1;i<order;i++) {
            temp[i]=spec[i];
            for (j=1;j<=i;j++) {
                spec[i]+=temp[i-j]*a[j];
            }
        }

        /* Now filter the rest */
        for (i=order;i<length;i++) {
            temp[i]=spec[i];
            for (j=1;j<=order;j++) {
                spec[i]+=temp[i-j]*a[j];
            }
        }
    }
    if (temp) FreeMemory(temp);
}





/*****************************************************/
/* TruncateCoeffs:                                   */
/*   Truncate the given reflection coeffs by zeroing */
/*   coefficients in the tail with absolute value    */
/*   less than the specified threshold.  Return the  */
/*   truncated filter order.                         */
/*****************************************************/
static int TruncateCoeffs(int fOrder,double threshold,double* kArray)
{
    int i;

    for (i = fOrder; i >= 0; i--) {
        kArray[i] = (fabs(kArray[i])>threshold) ? kArray[i] : 0.0;
        if (kArray[i]!=0.0) return i;
    }

    return 0;
}

/*****************************************************/
/* QuantizeReflectionCoeffs:                         */
/*   Quantize the given array of reflection coeffs   */
/*   to the specified resolution in bits.            */
/*****************************************************/
static void QuantizeReflectionCoeffs(int fOrder,
                              int coeffRes,
                              double* kArray,
                              int* indexArray)
{
    double iqfac,iqfac_m;
    int i;

    iqfac = ((1<<(coeffRes-1))-0.5)/(M_PI/2);
    iqfac_m = ((1<<(coeffRes-1))+0.5)/(M_PI/2);

    /* Quantize and inverse quantize */
    for (i=1;i<=fOrder;i++) {
        indexArray[i] = (int)(0.5+(asin(kArray[i])*((kArray[i]>=0)?iqfac:iqfac_m)));
        kArray[i] = sin((double)indexArray[i]/((indexArray[i]>=0)?iqfac:iqfac_m));
    }
}

/*****************************************************/
/* Autocorrelation,                                  */
/*   Compute the autocorrelation function            */
/*   estimate for the given data.                    */
/*****************************************************/
static void Autocorrelation(int maxOrder,        /* Maximum autocorr order */
                     int dataSize,        /* Size of the data array */
                     double* data,        /* Data array */
                     double* rArray)      /* Autocorrelation array */
{
    int order,index;

    for (order=0;order<=maxOrder;order++) {
        rArray[order]=0.0;
        for (index=0;index<dataSize;index++) {
            rArray[order]+=data[index]*data[index+order];
        }
        dataSize--;
    }
}



/*****************************************************/
/* LevinsonDurbin:                                   */
/*   Compute the reflection coefficients for the     */
/*   given data using LevinsonDurbin recursion.      */
/*   Return the prediction gain.                     */
/*****************************************************/
static double LevinsonDurbin(int fOrder,          /* Filter order */
                      int dataSize,        /* Size of the data array */
                      double* data,        /* Data array */
                      double* kArray)      /* Reflection coeff array */
{
    int order,i;
    double signal;
    double error, kTemp;                /* Prediction error */
    double aArray1[TNS_MAX_ORDER+1];    /* Predictor coeff array */
    double aArray2[TNS_MAX_ORDER+1];    /* Predictor coeff array 2 */
    double rArray[TNS_MAX_ORDER+1];     /* Autocorrelation coeffs */
    double* aPtr = aArray1;             /* Ptr to aArray1 */
    double* aLastPtr = aArray2;         /* Ptr to aArray2 */
    double* aTemp;

    /* Compute autocorrelation coefficients */
    Autocorrelation(fOrder,dataSize,data,rArray);
    signal=rArray[0];   /* signal energy */

    /* Set up pointers to current and last iteration */
    /* predictor coefficients.                       */
    aPtr = aArray1;
    aLastPtr = aArray2;
    /* If there is no signal energy, return */
    if (!signal) {
        kArray[0]=1.0;
        for (order=1;order<=fOrder;order++) {
            kArray[order]=0.0;
        }
        return 0;

    } else {

        /* Set up first iteration */
        kArray[0]=1.0;
        aPtr[0]=1.0;        /* Ptr to predictor coeffs, current iteration*/
        aLastPtr[0]=1.0;    /* Ptr to predictor coeffs, last iteration */
        error=rArray[0];

        /* Now perform recursion */
        for (order=1;order<=fOrder;order++) {
            kTemp = aLastPtr[0]*rArray[order-0];
            for (i=1;i<order;i++) {
                kTemp += aLastPtr[i]*rArray[order-i];
            }
            kTemp = -kTemp/error;
            kArray[order]=kTemp;
            aPtr[order]=kTemp;
            for (i=1;i<order;i++) {
                aPtr[i] = aLastPtr[i] + kTemp*aLastPtr[order-i];
            }
            error = error * (1 - kTemp*kTemp);

            /* Now make current iteration the last one */
            aTemp=aLastPtr;
            aLastPtr=aPtr;      /* Current becomes last */
            aPtr=aTemp;         /* Last becomes current */
        }
        return signal/error;    /* return the gain */
    }
}


/*****************************************************/
/* StepUp:                                           */
/*   Convert reflection coefficients into            */
/*   predictor coefficients.                         */
/*****************************************************/
static void StepUp(int fOrder,double* kArray,double* aArray)
{
    double aTemp[TNS_MAX_ORDER+2];
    int i,order;

    aArray[0]=1.0;
    aTemp[0]=1.0;
    for (order=1;order<=fOrder;order++) {
        aArray[order]=0.0;
        for (i=1;i<=order;i++) {
            aTemp[i] = aArray[i] + kArray[order]*aArray[order-i];
        }
        for (i=1;i<=order;i++) {
            aArray[i]=aTemp[i];
        }
    }
}