"Unfix" the filter length calculation

[openal-soft.git] / utils / makehrtf.c

/*
 * HRTF utility for producing and demonstrating the process of creating an
 * OpenAL Soft compatible HRIR data set.
 *
 * Copyright (C) 2011-2017  Christopher Fitzgerald
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Or visit:  http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
 *
 * --------------------------------------------------------------------------
 *
 * A big thanks goes out to all those whose work done in the field of
 * binaural sound synthesis using measured HRTFs makes this utility and the
 * OpenAL Soft implementation possible.
 *
 * The algorithm for diffuse-field equalization was adapted from the work
 * done by Rio Emmanuel and Larcher Veronique of IRCAM and Bill Gardner of
 * MIT Media Laboratory.  It operates as follows:
 *
 *  1.  Take the FFT of each HRIR and only keep the magnitude responses.
 *  2.  Calculate the diffuse-field power-average of all HRIRs weighted by
 *      their contribution to the total surface area covered by their
 *      measurement.
 *  3.  Take the diffuse-field average and limit its magnitude range.
 *  4.  Equalize the responses by using the inverse of the diffuse-field
 *      average.
 *  5.  Reconstruct the minimum-phase responses.
 *  5.  Zero the DC component.
 *  6.  IFFT the result and truncate to the desired-length minimum-phase FIR.
 *
 * The spherical head algorithm for calculating propagation delay was adapted
 * from the paper:
 *
 *  Modeling Interaural Time Difference Assuming a Spherical Head
 *  Joel David Miller
 *  Music 150, Musical Acoustics, Stanford University
 *  December 2, 2001
 *
 * The formulae for calculating the Kaiser window metrics are from the
 * the textbook:
 *
 *  Discrete-Time Signal Processing
 *  Alan V. Oppenheim and Ronald W. Schafer
 *  Prentice-Hall Signal Processing Series
 *  1999
 */

#include "config.h"

#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <string.h>
#include <limits.h>
#include <ctype.h>
#include <math.h>
#ifdef HAVE_STRINGS_H
#include <strings.h>
#endif

// Rely (if naively) on OpenAL's header for the types used for serialization.
#include "AL/al.h"
#include "AL/alext.h"

#ifndef M_PI
#define M_PI                         (3.14159265358979323846)
#endif

#ifndef HUGE_VAL
#define HUGE_VAL                     (1.0 / 0.0)
#endif

// The epsilon used to maintain signal stability.
#define EPSILON                      (1e-9)

// Constants for accessing the token reader's ring buffer.
#define TR_RING_BITS                 (16)
#define TR_RING_SIZE                 (1 << TR_RING_BITS)
#define TR_RING_MASK                 (TR_RING_SIZE - 1)

// The token reader's load interval in bytes.
#define TR_LOAD_SIZE                 (TR_RING_SIZE >> 2)

// The maximum identifier length used when processing the data set
// definition.
#define MAX_IDENT_LEN                (16)

// The maximum path length used when processing filenames.
#define MAX_PATH_LEN                 (256)

// The limits for the sample 'rate' metric in the data set definition and for
// resampling.
#define MIN_RATE                     (32000)
#define MAX_RATE                     (96000)

// The limits for the HRIR 'points' metric in the data set definition.
#define MIN_POINTS                   (16)
#define MAX_POINTS                   (8192)

// The limits to the number of 'azimuths' listed in the data set definition.
#define MIN_EV_COUNT                 (5)
#define MAX_EV_COUNT                 (128)

// The limits for each of the 'azimuths' listed in the data set definition.
#define MIN_AZ_COUNT                 (1)
#define MAX_AZ_COUNT                 (128)

// The limits for the listener's head 'radius' in the data set definition.
#define MIN_RADIUS                   (0.05)
#define MAX_RADIUS                   (0.15)

// The limits for the 'distance' from source to listener in the definition
// file.
#define MIN_DISTANCE                 (0.5)
#define MAX_DISTANCE                 (2.5)

// The maximum number of channels that can be addressed for a WAVE file
// source listed in the data set definition.
#define MAX_WAVE_CHANNELS            (65535)

// The limits to the byte size for a binary source listed in the definition
// file.
#define MIN_BIN_SIZE                 (2)
#define MAX_BIN_SIZE                 (4)

// The minimum number of significant bits for binary sources listed in the
// data set definition.  The maximum is calculated from the byte size.
#define MIN_BIN_BITS                 (16)

// The limits to the number of significant bits for an ASCII source listed in
// the data set definition.
#define MIN_ASCII_BITS               (16)
#define MAX_ASCII_BITS               (32)

// The limits to the FFT window size override on the command line.
#define MIN_FFTSIZE                  (65536)
#define MAX_FFTSIZE                  (131072)

// The limits to the equalization range limit on the command line.
#define MIN_LIMIT                    (2.0)
#define MAX_LIMIT                    (120.0)

// The limits to the truncation window size on the command line.
#define MIN_TRUNCSIZE                (16)
#define MAX_TRUNCSIZE                (512)

// The limits to the custom head radius on the command line.
#define MIN_CUSTOM_RADIUS            (0.05)
#define MAX_CUSTOM_RADIUS            (0.15)

// The truncation window size must be a multiple of the below value to allow
// for vectorized convolution.
#define MOD_TRUNCSIZE                (8)

// The defaults for the command line options.
#define DEFAULT_FFTSIZE              (65536)
#define DEFAULT_EQUALIZE             (1)
#define DEFAULT_SURFACE              (1)
#define DEFAULT_LIMIT                (24.0)
#define DEFAULT_TRUNCSIZE            (32)
#define DEFAULT_HEAD_MODEL           (HM_DATASET)
#define DEFAULT_CUSTOM_RADIUS        (0.0)

// The four-character-codes for RIFF/RIFX WAVE file chunks.
#define FOURCC_RIFF                  (0x46464952) // 'RIFF'
#define FOURCC_RIFX                  (0x58464952) // 'RIFX'
#define FOURCC_WAVE                  (0x45564157) // 'WAVE'
#define FOURCC_FMT                   (0x20746D66) // 'fmt '
#define FOURCC_DATA                  (0x61746164) // 'data'
#define FOURCC_LIST                  (0x5453494C) // 'LIST'
#define FOURCC_WAVL                  (0x6C766177) // 'wavl'
#define FOURCC_SLNT                  (0x746E6C73) // 'slnt'

// The supported wave formats.
#define WAVE_FORMAT_PCM              (0x0001)
#define WAVE_FORMAT_IEEE_FLOAT       (0x0003)
#define WAVE_FORMAT_EXTENSIBLE       (0xFFFE)

// The maximum propagation delay value supported by OpenAL Soft.
#define MAX_HRTD                     (63.0)

// The OpenAL Soft HRTF format marker.  It stands for minimum-phase head
// response protocol 01.
#define MHR_FORMAT                   ("MinPHR01")

#define MHR_FORMAT_EXPERIMENTAL      ("MinPHRTEMPDONOTUSE")

// Sample and channel type enum values
typedef enum SampleTypeT {
    ST_S16 = 0,
    ST_S24 = 1
} SampleTypeT;

typedef enum ChannelTypeT {
    CT_LEFTONLY  = 0,
    CT_LEFTRIGHT = 1
} ChannelTypeT;

// Byte order for the serialization routines.
typedef enum ByteOrderT {
    BO_NONE,
    BO_LITTLE,
    BO_BIG
} ByteOrderT;

// Source format for the references listed in the data set definition.
typedef enum SourceFormatT {
    SF_NONE,
    SF_WAVE,   // RIFF/RIFX WAVE file.
    SF_BIN_LE, // Little-endian binary file.
    SF_BIN_BE, // Big-endian binary file.
    SF_ASCII   // ASCII text file.
} SourceFormatT;

// Element types for the references listed in the data set definition.
typedef enum ElementTypeT {
    ET_NONE,
    ET_INT,   // Integer elements.
    ET_FP    // Floating-point elements.
} ElementTypeT;

// Head model used for calculating the impulse delays.
typedef enum HeadModelT {
    HM_NONE,
    HM_DATASET, // Measure the onset from the dataset.
    HM_SPHERE   // Calculate the onset using a spherical head model.
} HeadModelT;

// Desired output format from the command line.
typedef enum OutputFormatT {
    OF_NONE,
    OF_MHR   // OpenAL Soft MHR data set file.
} OutputFormatT;

// Unsigned integer type.
typedef unsigned int uint;

// Serialization types.  The trailing digit indicates the number of bits.
typedef ALubyte      uint8;
typedef ALint        int32;
typedef ALuint       uint32;
typedef ALuint64SOFT uint64;

// Token reader state for parsing the data set definition.
typedef struct TokenReaderT {
    FILE *mFile;
    const char *mName;
    uint        mLine;
    uint        mColumn;
    char   mRing[TR_RING_SIZE];
    size_t mIn;
    size_t mOut;
} TokenReaderT;

// Source reference state used when loading sources.
typedef struct SourceRefT {
    SourceFormatT mFormat;
    ElementTypeT  mType;
    uint mSize;
    int  mBits;
    uint mChannel;
    uint mSkip;
    uint mOffset;
    char mPath[MAX_PATH_LEN+1];
} SourceRefT;

// The HRIR metrics and data set used when loading, processing, and storing
// the resulting HRTF.
typedef struct HrirDataT {
    uint mIrRate;
    SampleTypeT mSampleType;
    ChannelTypeT mChannelType;
    uint mIrCount;
    uint mIrSize;
    uint mIrPoints;
    uint mFftSize;
    uint mEvCount;
    uint mEvStart;
    uint mAzCount[MAX_EV_COUNT];
    uint mEvOffset[MAX_EV_COUNT];
    double mRadius;
    double mDistance;
    double *mHrirs;
    double *mHrtds;
    double  mMaxHrtd;
} HrirDataT;

// The resampler metrics and FIR filter.
typedef struct ResamplerT {
    uint mP, mQ, mM, mL;
    double *mF;
} ResamplerT;


/*****************************
 *** Token reader routines ***
 *****************************/

/* Whitespace is not significant. It can process tokens as identifiers, numbers
 * (integer and floating-point), strings, and operators. Strings must be
 * encapsulated by double-quotes and cannot span multiple lines.
 */

// Setup the reader on the given file.  The filename can be NULL if no error
// output is desired.
static void TrSetup(FILE *fp, const char *filename, TokenReaderT *tr)
{
    const char *name = NULL;

    if(filename)
    {
        const char *slash = strrchr(filename, '/');
        if(slash)
        {
            const char *bslash = strrchr(slash+1, '\\');
            if(bslash) name = bslash+1;
            else name = slash+1;
        }
        else
        {
            const char *bslash = strrchr(filename, '\\');
            if(bslash) name = bslash+1;
            else name = filename;
        }
    }

    tr->mFile = fp;
    tr->mName = name;
    tr->mLine = 1;
    tr->mColumn = 1;
    tr->mIn = 0;
    tr->mOut = 0;
}

// Prime the reader's ring buffer, and return a result indicating that there
// is text to process.
static int TrLoad(TokenReaderT *tr)
{
    size_t toLoad, in, count;

    toLoad = TR_RING_SIZE - (tr->mIn - tr->mOut);
    if(toLoad >= TR_LOAD_SIZE && !feof(tr->mFile))
    {
        // Load TR_LOAD_SIZE (or less if at the end of the file) per read.
        toLoad = TR_LOAD_SIZE;
        in = tr->mIn&TR_RING_MASK;
        count = TR_RING_SIZE - in;
        if(count < toLoad)
        {
            tr->mIn += fread(&tr->mRing[in], 1, count, tr->mFile);
            tr->mIn += fread(&tr->mRing[0], 1, toLoad-count, tr->mFile);
        }
        else
            tr->mIn += fread(&tr->mRing[in], 1, toLoad, tr->mFile);

        if(tr->mOut >= TR_RING_SIZE)
        {
            tr->mOut -= TR_RING_SIZE;
            tr->mIn -= TR_RING_SIZE;
        }
    }
    if(tr->mIn > tr->mOut)
        return 1;
    return 0;
}

// Error display routine.  Only displays when the base name is not NULL.
static void TrErrorVA(const TokenReaderT *tr, uint line, uint column, const char *format, va_list argPtr)
{
    if(!tr->mName)
        return;
    fprintf(stderr, "Error (%s:%u:%u): ", tr->mName, line, column);
    vfprintf(stderr, format, argPtr);
}

// Used to display an error at a saved line/column.
static void TrErrorAt(const TokenReaderT *tr, uint line, uint column, const char *format, ...)
{
    va_list argPtr;

    va_start(argPtr, format);
    TrErrorVA(tr, line, column, format, argPtr);
    va_end(argPtr);
}

// Used to display an error at the current line/column.
static void TrError(const TokenReaderT *tr, const char *format, ...)
{
    va_list argPtr;

    va_start(argPtr, format);
    TrErrorVA(tr, tr->mLine, tr->mColumn, format, argPtr);
    va_end(argPtr);
}

// Skips to the next line.
static void TrSkipLine(TokenReaderT *tr)
{
    char ch;

    while(TrLoad(tr))
    {
        ch = tr->mRing[tr->mOut&TR_RING_MASK];
        tr->mOut++;
        if(ch == '\n')
        {
            tr->mLine++;
            tr->mColumn = 1;
            break;
        }
        tr->mColumn ++;
    }
}

// Skips to the next token.
static int TrSkipWhitespace(TokenReaderT *tr)
{
    char ch;

    while(TrLoad(tr))
    {
        ch = tr->mRing[tr->mOut&TR_RING_MASK];
        if(isspace(ch))
        {
            tr->mOut++;
            if(ch == '\n')
            {
                tr->mLine++;
                tr->mColumn = 1;
            }
            else
                tr->mColumn++;
        }
        else if(ch == '#')
            TrSkipLine(tr);
        else
            return 1;
    }
    return 0;
}

// Get the line and/or column of the next token (or the end of input).
static void TrIndication(TokenReaderT *tr, uint *line, uint *column)
{
    TrSkipWhitespace(tr);
    if(line) *line = tr->mLine;
    if(column) *column = tr->mColumn;
}

// Checks to see if a token is the given operator.  It does not display any
// errors and will not proceed to the next token.
static int TrIsOperator(TokenReaderT *tr, const char *op)
{
    size_t out, len;
    char ch;

    if(!TrSkipWhitespace(tr))
        return 0;
    out = tr->mOut;
    len = 0;
    while(op[len] != '\0' && out < tr->mIn)
    {
        ch = tr->mRing[out&TR_RING_MASK];
        if(ch != op[len]) break;
        len++;
        out++;
    }
    if(op[len] == '\0')
        return 1;
    return 0;
}

/* The TrRead*() routines obtain the value of a matching token type.  They
 * display type, form, and boundary errors and will proceed to the next
 * token.
 */

// Reads and validates an identifier token.
static int TrReadIdent(TokenReaderT *tr, const uint maxLen, char *ident)
{
    uint col, len;
    char ch;

    col = tr->mColumn;
    if(TrSkipWhitespace(tr))
    {
        col = tr->mColumn;
        ch = tr->mRing[tr->mOut&TR_RING_MASK];
        if(ch == '_' || isalpha(ch))
        {
            len = 0;
            do {
                if(len < maxLen)
                    ident[len] = ch;
                len++;
                tr->mOut++;
                if(!TrLoad(tr))
                    break;
                ch = tr->mRing[tr->mOut&TR_RING_MASK];
            } while(ch == '_' || isdigit(ch) || isalpha(ch));

            tr->mColumn += len;
            if(len < maxLen)
            {
                ident[len] = '\0';
                return 1;
            }
            TrErrorAt(tr, tr->mLine, col, "Identifier is too long.\n");
            return 0;
        }
    }
    TrErrorAt(tr, tr->mLine, col, "Expected an identifier.\n");
    return 0;
}

// Reads and validates (including bounds) an integer token.
static int TrReadInt(TokenReaderT *tr, const int loBound, const int hiBound, int *value)
{
    uint col, digis, len;
    char ch, temp[64+1];

    col = tr->mColumn;
    if(TrSkipWhitespace(tr))
    {
        col = tr->mColumn;
        len = 0;
        ch = tr->mRing[tr->mOut&TR_RING_MASK];
        if(ch == '+' || ch == '-')
        {
            temp[len] = ch;
            len++;
            tr->mOut++;
        }
        digis = 0;
        while(TrLoad(tr))
        {
            ch = tr->mRing[tr->mOut&TR_RING_MASK];
            if(!isdigit(ch)) break;
            if(len < 64)
                temp[len] = ch;
            len++;
            digis++;
            tr->mOut++;
        }
        tr->mColumn += len;
        if(digis > 0 && ch != '.' && !isalpha(ch))
        {
            if(len > 64)
            {
                TrErrorAt(tr, tr->mLine, col, "Integer is too long.");
                return 0;
            }
            temp[len] = '\0';
            *value = strtol(temp, NULL, 10);
            if(*value < loBound || *value > hiBound)
            {
                TrErrorAt(tr, tr->mLine, col, "Expected a value from %d to %d.\n", loBound, hiBound);
                return (0);
            }
            return (1);
        }
    }
    TrErrorAt(tr, tr->mLine, col, "Expected an integer.\n");
    return 0;
}

// Reads and validates (including bounds) a float token.
static int TrReadFloat(TokenReaderT *tr, const double loBound, const double hiBound, double *value)
{
    uint col, digis, len;
    char ch, temp[64+1];

    col = tr->mColumn;
    if(TrSkipWhitespace(tr))
    {
        col = tr->mColumn;
        len = 0;
        ch = tr->mRing[tr->mOut&TR_RING_MASK];
        if(ch == '+' || ch == '-')
        {
            temp[len] = ch;
            len++;
            tr->mOut++;
        }

        digis = 0;
        while(TrLoad(tr))
        {
            ch = tr->mRing[tr->mOut&TR_RING_MASK];
            if(!isdigit(ch)) break;
            if(len < 64)
                temp[len] = ch;
            len++;
            digis++;
            tr->mOut++;
        }
        if(ch == '.')
        {
            if(len < 64)
                temp[len] = ch;
            len++;
            tr->mOut++;
        }
        while(TrLoad(tr))
        {
            ch = tr->mRing[tr->mOut&TR_RING_MASK];
            if(!isdigit(ch)) break;
            if(len < 64)
                temp[len] = ch;
            len++;
            digis++;
            tr->mOut++;
        }
        if(digis > 0)
        {
            if(ch == 'E' || ch == 'e')
            {
                if(len < 64)
                    temp[len] = ch;
                len++;
                digis = 0;
                tr->mOut++;
                if(ch == '+' || ch == '-')
                {
                    if(len < 64)
                        temp[len] = ch;
                    len++;
                    tr->mOut++;
                }
                while(TrLoad(tr))
                {
                    ch = tr->mRing[tr->mOut&TR_RING_MASK];
                    if(!isdigit(ch)) break;
                    if(len < 64)
                        temp[len] = ch;
                    len++;
                    digis++;
                    tr->mOut++;
                }
            }
            tr->mColumn += len;
            if(digis > 0 && ch != '.' && !isalpha(ch))
            {
                if(len > 64)
                {
                    TrErrorAt(tr, tr->mLine, col, "Float is too long.");
                    return 0;
                }
                temp[len] = '\0';
                *value = strtod(temp, NULL);
                if(*value < loBound || *value > hiBound)
                {
                    TrErrorAt (tr, tr->mLine, col, "Expected a value from %f to %f.\n", loBound, hiBound);
                    return 0;
                }
                return 1;
            }
        }
        else
            tr->mColumn += len;
    }
    TrErrorAt(tr, tr->mLine, col, "Expected a float.\n");
    return 0;
}

// Reads and validates a string token.
static int TrReadString(TokenReaderT *tr, const uint maxLen, char *text)
{
    uint col, len;
    char ch;

    col = tr->mColumn;
    if(TrSkipWhitespace(tr))
    {
        col = tr->mColumn;
        ch = tr->mRing[tr->mOut&TR_RING_MASK];
        if(ch == '\"')
        {
            tr->mOut++;
            len = 0;
            while(TrLoad(tr))
            {
                ch = tr->mRing[tr->mOut&TR_RING_MASK];
                tr->mOut++;
                if(ch == '\"')
                    break;
                if(ch == '\n')
                {
                    TrErrorAt (tr, tr->mLine, col, "Unterminated string at end of line.\n");
                    return 0;
                }
                if(len < maxLen)
                    text[len] = ch;
                len++;
            }
            if(ch != '\"')
            {
                tr->mColumn += 1 + len;
                TrErrorAt(tr, tr->mLine, col, "Unterminated string at end of input.\n");
                return 0;
            }
            tr->mColumn += 2 + len;
            if(len > maxLen)
            {
                TrErrorAt (tr, tr->mLine, col, "String is too long.\n");
                return 0;
            }
            text[len] = '\0';
            return 1;
        }
    }
    TrErrorAt(tr, tr->mLine, col, "Expected a string.\n");
    return 0;
}

// Reads and validates the given operator.
static int TrReadOperator(TokenReaderT *tr, const char *op)
{
    uint col, len;
    char ch;

    col = tr->mColumn;
    if(TrSkipWhitespace(tr))
    {
        col = tr->mColumn;
        len = 0;
        while(op[len] != '\0' && TrLoad(tr))
        {
            ch = tr->mRing[tr->mOut&TR_RING_MASK];
            if(ch != op[len]) break;
            len++;
            tr->mOut++;
        }
        tr->mColumn += len;
        if(op[len] == '\0')
            return 1;
    }
    TrErrorAt(tr, tr->mLine, col, "Expected '%s' operator.\n", op);
    return 0;
}

/* Performs a string substitution.  Any case-insensitive occurrences of the
 * pattern string are replaced with the replacement string.  The result is
 * truncated if necessary.
 */
static int StrSubst(const char *in, const char *pat, const char *rep, const size_t maxLen, char *out)
{
    size_t inLen, patLen, repLen;
    size_t si, di;
    int truncated;

    inLen = strlen(in);
    patLen = strlen(pat);
    repLen = strlen(rep);
    si = 0;
    di = 0;
    truncated = 0;
    while(si < inLen && di < maxLen)
    {
        if(patLen <= inLen-si)
        {
            if(strncasecmp(&in[si], pat, patLen) == 0)
            {
                if(repLen > maxLen-di)
                {
                    repLen = maxLen - di;
                    truncated = 1;
                }
                strncpy(&out[di], rep, repLen);
                si += patLen;
                di += repLen;
            }
        }
        out[di] = in[si];
        si++;
        di++;
    }
    if(si < inLen)
        truncated = 1;
    out[di] = '\0';
    return !truncated;
}


/*********************
 *** Math routines ***
 *********************/

// Provide missing math routines for MSVC versions < 1800 (Visual Studio 2013).
#if defined(_MSC_VER) && _MSC_VER < 1800
static double round(double val)
{
    if(val < 0.0)
        return ceil(val-0.5);
    return floor(val+0.5);
}

static double fmin(double a, double b)
{
    return (a<b) ? a : b;
}

static double fmax(double a, double b)
{
    return (a>b) ? a : b;
}
#endif

// Simple clamp routine.
static double Clamp(const double val, const double lower, const double upper)
{
    return fmin(fmax(val, lower), upper);
}

// Performs linear interpolation.
static double Lerp(const double a, const double b, const double f)
{
    return a + (f * (b - a));
}

static inline uint dither_rng(uint *seed)
{
    *seed = (*seed * 96314165) + 907633515;
    return *seed;
}

// Performs a triangular probability density function dither. It assumes the
// input sample is already scaled.
static inline double TpdfDither(const double in, uint *seed)
{
    static const double PRNG_SCALE = 1.0 / UINT_MAX;
    uint prn0, prn1;

    prn0 = dither_rng(seed);
    prn1 = dither_rng(seed);
    return round(in + (prn0*PRNG_SCALE - prn1*PRNG_SCALE));
}

// Allocates an array of doubles.
static double *CreateArray(size_t n)
{
    double *a;

    if(n == 0) n = 1;
    a = calloc(n, sizeof(double));
    if(a == NULL)
    {
        fprintf(stderr, "Error:  Out of memory.\n");
        exit(-1);
    }
    return a;
}

// Frees an array of doubles.
static void DestroyArray(double *a)
{ free(a); }

// Complex number routines.  All outputs must be non-NULL.

// Magnitude/absolute value.
static double ComplexAbs(const double r, const double i)
{
    return sqrt(r*r + i*i);
}

// Multiply.
static void ComplexMul(const double aR, const double aI, const double bR, const double bI, double *outR, double *outI)
{
    *outR = (aR * bR) - (aI * bI);
    *outI = (aI * bR) + (aR * bI);
}

// Base-e exponent.
static void ComplexExp(const double inR, const double inI, double *outR, double *outI)
{
    double e = exp(inR);
    *outR = e * cos(inI);
    *outI = e * sin(inI);
}

/* Fast Fourier transform routines.  The number of points must be a power of
 * two.  In-place operation is possible only if both the real and imaginary
 * parts are in-place together.
 */

// Performs bit-reversal ordering.
static void FftArrange(const uint n, const double *inR, const double *inI, double *outR, double *outI)
{
    uint rk, k, m;
    double tempR, tempI;

    if(inR == outR && inI == outI)
    {
        // Handle in-place arrangement.
        rk = 0;
        for(k = 0;k < n;k++)
        {
            if(rk > k)
            {
                tempR = inR[rk];
                tempI = inI[rk];
                outR[rk] = inR[k];
                outI[rk] = inI[k];
                outR[k] = tempR;
                outI[k] = tempI;
            }
            m = n;
            while(rk&(m >>= 1))
                rk &= ~m;
            rk |= m;
        }
    }
    else
    {
        // Handle copy arrangement.
        rk = 0;
        for(k = 0;k < n;k++)
        {
            outR[rk] = inR[k];
            outI[rk] = inI[k];
            m = n;
            while(rk&(m >>= 1))
                rk &= ~m;
            rk |= m;
        }
    }
}

// Performs the summation.
static void FftSummation(const uint n, const double s, double *re, double *im)
{
    double pi;
    uint m, m2;
    double vR, vI, wR, wI;
    uint i, k, mk;
    double tR, tI;

    pi = s * M_PI;
    for(m = 1, m2 = 2;m < n; m <<= 1, m2 <<= 1)
    {
        // v = Complex (-2.0 * sin (0.5 * pi / m) * sin (0.5 * pi / m), -sin (pi / m))
        vR = sin(0.5 * pi / m);
        vR = -2.0 * vR * vR;
        vI = -sin(pi / m);
        // w = Complex (1.0, 0.0)
        wR = 1.0;
        wI = 0.0;
        for(i = 0;i < m;i++)
        {
            for(k = i;k < n;k += m2)
            {
                mk = k + m;
                // t = ComplexMul(w, out[km2])
                tR = (wR * re[mk]) - (wI * im[mk]);
                tI = (wR * im[mk]) + (wI * re[mk]);
                // out[mk] = ComplexSub (out [k], t)
                re[mk] = re[k] - tR;
                im[mk] = im[k] - tI;
                // out[k] = ComplexAdd (out [k], t)
                re[k] += tR;
                im[k] += tI;
            }
            // t = ComplexMul (v, w)
            tR = (vR * wR) - (vI * wI);
            tI = (vR * wI) + (vI * wR);
            // w = ComplexAdd (w, t)
            wR += tR;
            wI += tI;
        }
    }
}

// Performs a forward FFT.
static void FftForward(const uint n, const double *inR, const double *inI, double *outR, double *outI)
{
    FftArrange(n, inR, inI, outR, outI);
    FftSummation(n, 1.0, outR, outI);
}

// Performs an inverse FFT.
static void FftInverse(const uint n, const double *inR, const double *inI, double *outR, double *outI)
{
    double f;
    uint i;

    FftArrange(n, inR, inI, outR, outI);
    FftSummation(n, -1.0, outR, outI);
    f = 1.0 / n;
    for(i = 0;i < n;i++)
    {
        outR[i] *= f;
        outI[i] *= f;
    }
}

/* Calculate the complex helical sequence (or discrete-time analytical signal)
 * of the given input using the Hilbert transform. Given the natural logarithm
 * of a signal's magnitude response, the imaginary components can be used as
 * the angles for minimum-phase reconstruction.
 */
static void Hilbert(const uint n, const double *in, double *outR, double *outI)
{
    uint i;

    if(in == outR)
    {
        // Handle in-place operation.
        for(i = 0;i < n;i++)
            outI[i] = 0.0;
    }
    else
    {
        // Handle copy operation.
        for(i = 0;i < n;i++)
        {
            outR[i] = in[i];
            outI[i] = 0.0;
        }
    }
    FftInverse(n, outR, outI, outR, outI);
    for(i = 1;i < (n+1)/2;i++)
    {
        outR[i] *= 2.0;
        outI[i] *= 2.0;
    }
    /* Increment i if n is even. */
    i += (n&1)^1;
    for(;i < n;i++)
    {
        outR[i] = 0.0;
        outI[i] = 0.0;
    }
    FftForward(n, outR, outI, outR, outI);
}

/* Calculate the magnitude response of the given input.  This is used in
 * place of phase decomposition, since the phase residuals are discarded for
 * minimum phase reconstruction.  The mirrored half of the response is also
 * discarded.
 */
static void MagnitudeResponse(const uint n, const double *inR, const double *inI, double *out)
{
    const uint m = 1 + (n / 2);
    uint i;
    for(i = 0;i < m;i++)
        out[i] = fmax(ComplexAbs(inR[i], inI[i]), EPSILON);
}

/* Apply a range limit (in dB) to the given magnitude response.  This is used
 * to adjust the effects of the diffuse-field average on the equalization
 * process.
 */
static void LimitMagnitudeResponse(const uint n, const double limit, const double *in, double *out)
{
    const uint m = 1 + (n / 2);
    double halfLim;
    uint i, lower, upper;
    double ave;

    halfLim = limit / 2.0;
    // Convert the response to dB.
    for(i = 0;i < m;i++)
        out[i] = 20.0 * log10(in[i]);
    // Use six octaves to calculate the average magnitude of the signal.
    lower = ((uint)ceil(n / pow(2.0, 8.0))) - 1;
    upper = ((uint)floor(n / pow(2.0, 2.0))) - 1;
    ave = 0.0;
    for(i = lower;i <= upper;i++)
        ave += out[i];
    ave /= upper - lower + 1;
    // Keep the response within range of the average magnitude.
    for(i = 0;i < m;i++)
        out[i] = Clamp(out[i], ave - halfLim, ave + halfLim);
    // Convert the response back to linear magnitude.
    for(i = 0;i < m;i++)
        out[i] = pow(10.0, out[i] / 20.0);
}

/* Reconstructs the minimum-phase component for the given magnitude response
 * of a signal.  This is equivalent to phase recomposition, sans the missing
 * residuals (which were discarded).  The mirrored half of the response is
 * reconstructed.
 */
static void MinimumPhase(const uint n, const double *in, double *outR, double *outI)
{
    const uint m = 1 + (n / 2);
    double *mags;
    double aR, aI;
    uint i;

    mags = CreateArray(n);
    for(i = 0;i < m;i++)
    {
        mags[i] = fmax(EPSILON, in[i]);
        outR[i] = log(mags[i]);
    }
    for(;i < n;i++)
    {
        mags[i] = mags[n - i];
        outR[i] = outR[n - i];
    }
    Hilbert(n, outR, outR, outI);
    // Remove any DC offset the filter has.
    mags[0] = EPSILON;
    for(i = 0;i < n;i++)
    {
        ComplexExp(0.0, outI[i], &aR, &aI);
        ComplexMul(mags[i], 0.0, aR, aI, &outR[i], &outI[i]);
    }
    DestroyArray(mags);
}


/***************************
 *** Resampler functions ***
 ***************************/

/* This is the normalized cardinal sine (sinc) function.
 *
 *   sinc(x) = { 1,                   x = 0
 *             { sin(pi x) / (pi x),  otherwise.
 */
static double Sinc(const double x)
{
    if(fabs(x) < EPSILON)
        return 1.0;
    return sin(M_PI * x) / (M_PI * x);
}

/* The zero-order modified Bessel function of the first kind, used for the
 * Kaiser window.
 *
 *   I_0(x) = sum_{k=0}^inf (1 / k!)^2 (x / 2)^(2 k)
 *          = sum_{k=0}^inf ((x / 2)^k / k!)^2
 */
static double BesselI_0(const double x)
{
    double term, sum, x2, y, last_sum;
    int k;

    // Start at k=1 since k=0 is trivial.
    term = 1.0;
    sum = 1.0;
    x2 = x/2.0;
    k = 1;

    // Let the integration converge until the term of the sum is no longer
    // significant.
    do {
        y = x2 / k;
        k++;
        last_sum = sum;
        term *= y * y;
        sum += term;
    } while(sum != last_sum);
    return sum;
}

/* Calculate a Kaiser window from the given beta value and a normalized k
 * [-1, 1].
 *
 *   w(k) = { I_0(B sqrt(1 - k^2)) / I_0(B),  -1 <= k <= 1
 *          { 0,                              elsewhere.
 *
 * Where k can be calculated as:
 *
 *   k = i / l,         where -l <= i <= l.
 *
 * or:
 *
 *   k = 2 i / M - 1,   where 0 <= i <= M.
 */
static double Kaiser(const double b, const double k)
{
    if(!(k >= -1.0 && k <= 1.0))
        return 0.0;
    return BesselI_0(b * sqrt(1.0 - k*k)) / BesselI_0(b);
}

// Calculates the greatest common divisor of a and b.
static uint Gcd(uint x, uint y)
{
    while(y > 0)
    {
        uint z = y;
        y = x % y;
        x = z;
    }
    return x;
}

/* Calculates the size (order) of the Kaiser window.  Rejection is in dB and
 * the transition width is normalized frequency (0.5 is nyquist).
 *
 *   M = { ceil((r - 7.95) / (2.285 2 pi f_t)),  r > 21
 *       { ceil(5.79 / 2 pi f_t),                r <= 21.
 *
 */
static uint CalcKaiserOrder(const double rejection, const double transition)
{
    double w_t = 2.0 * M_PI * transition;
    if(rejection > 21.0)
        return (uint)ceil((rejection - 7.95) / (2.285 * w_t));
    return (uint)ceil(5.79 / w_t);
}

// Calculates the beta value of the Kaiser window.  Rejection is in dB.
static double CalcKaiserBeta(const double rejection)
{
    if(rejection > 50.0)
        return 0.1102 * (rejection - 8.7);
    if(rejection >= 21.0)
        return (0.5842 * pow(rejection - 21.0, 0.4)) +
               (0.07886 * (rejection - 21.0));
    return 0.0;
}

/* Calculates a point on the Kaiser-windowed sinc filter for the given half-
 * width, beta, gain, and cutoff.  The point is specified in non-normalized
 * samples, from 0 to M, where M = (2 l + 1).
 *
 *   w(k) 2 p f_t sinc(2 f_t x)
 *
 *   x    -- centered sample index (i - l)
 *   k    -- normalized and centered window index (x / l)
 *   w(k) -- window function (Kaiser)
 *   p    -- gain compensation factor when sampling
 *   f_t  -- normalized center frequency (or cutoff; 0.5 is nyquist)
 */
static double SincFilter(const int l, const double b, const double gain, const double cutoff, const int i)
{
    return Kaiser(b, (double)(i - l) / l) * 2.0 * gain * cutoff * Sinc(2.0 * cutoff * (i - l));
}

/* This is a polyphase sinc-filtered resampler.
 *
 *              Upsample                      Downsample
 *
 *              p/q = 3/2                     p/q = 3/5
 *
 *          M-+-+-+->                     M-+-+-+->
 *         -------------------+          ---------------------+
 *   p  s * f f f f|f|        |    p  s * f f f f f           |
 *   |  0 *   0 0 0|0|0       |    |  0 *   0 0 0 0|0|        |
 *   v  0 *     0 0|0|0 0     |    v  0 *     0 0 0|0|0       |
 *      s *       f|f|f f f   |       s *       f f|f|f f     |
 *      0 *        |0|0 0 0 0 |       0 *         0|0|0 0 0   |
 *         --------+=+--------+       0 *          |0|0 0 0 0 |
 *          d . d .|d|. d . d            ----------+=+--------+
 *                                        d . . . .|d|. . . .
 *          q->
 *                                        q-+-+-+->
 *
 *   P_f(i,j) = q i mod p + pj
 *   P_s(i,j) = floor(q i / p) - j
 *   d[i=0..N-1] = sum_{j=0}^{floor((M - 1) / p)} {
 *                   { f[P_f(i,j)] s[P_s(i,j)],  P_f(i,j) < M
 *                   { 0,                        P_f(i,j) >= M. }
 */

// Calculate the resampling metrics and build the Kaiser-windowed sinc filter
// that's used to cut frequencies above the destination nyquist.
static void ResamplerSetup(ResamplerT *rs, const uint srcRate, const uint dstRate)
{
    double cutoff, width, beta;
    uint gcd, l;
    int i;

    gcd = Gcd(srcRate, dstRate);
    rs->mP = dstRate / gcd;
    rs->mQ = srcRate / gcd;
    /* The cutoff is adjusted by half the transition width, so the transition
     * ends before the nyquist (0.5).  Both are scaled by the downsampling
     * factor.
     */
    if(rs->mP > rs->mQ)
    {
        cutoff = 0.475 / rs->mP;
        width = 0.05 / rs->mP;
    }
    else
    {
        cutoff = 0.475 / rs->mQ;
        width = 0.05 / rs->mQ;
    }
    // A rejection of -180 dB is used for the stop band. Round up when
    // calculating the left offset to avoid increasing the transition width.
    l = (CalcKaiserOrder(180.0, width)+1) / 2;
    beta = CalcKaiserBeta(180.0);
    rs->mM = l*2 + 1;
    rs->mL = l;
    rs->mF = CreateArray(rs->mM);
    for(i = 0;i < ((int)rs->mM);i++)
        rs->mF[i] = SincFilter((int)l, beta, rs->mP, cutoff, i);
}

// Clean up after the resampler.
static void ResamplerClear(ResamplerT *rs)
{
    DestroyArray(rs->mF);
    rs->mF = NULL;
}

// Perform the upsample-filter-downsample resampling operation using a
// polyphase filter implementation.
static void ResamplerRun(ResamplerT *rs, const uint inN, const double *in, const uint outN, double *out)
{
    const uint p = rs->mP, q = rs->mQ, m = rs->mM, l = rs->mL;
    const double *f = rs->mF;
    uint j_f, j_s;
    double *work;
    uint i;

    if(outN == 0)
        return;

    // Handle in-place operation.
    if(in == out)
        work = CreateArray(outN);
    else
        work = out;
    // Resample the input.
    for(i = 0;i < outN;i++)
    {
        double r = 0.0;
        // Input starts at l to compensate for the filter delay.  This will
        // drop any build-up from the first half of the filter.
        j_f = (l + (q * i)) % p;
        j_s = (l + (q * i)) / p;
        while(j_f < m)
        {
            // Only take input when 0 <= j_s < inN.  This single unsigned
            // comparison catches both cases.
            if(j_s < inN)
                r += f[j_f] * in[j_s];
            j_f += p;
            j_s--;
        }
        work[i] = r;
    }
    // Clean up after in-place operation.
    if(in == out)
    {
        for(i = 0;i < outN;i++)
            out[i] = work[i];
        DestroyArray(work);
    }
}

/*************************
 *** File source input ***
 *************************/

// Read a binary value of the specified byte order and byte size from a file,
// storing it as a 32-bit unsigned integer.
static int ReadBin4(FILE *fp, const char *filename, const ByteOrderT order, const uint bytes, uint32 *out)
{
    uint8 in[4];
    uint32 accum;
    uint i;

    if(fread(in, 1, bytes, fp) != bytes)
    {
        fprintf(stderr, "Error: Bad read from file '%s'.\n", filename);
        return 0;
    }
    accum = 0;
    switch(order)
    {
        case BO_LITTLE:
            for(i = 0;i < bytes;i++)
                accum = (accum<<8) | in[bytes - i - 1];
            break;
        case BO_BIG:
            for(i = 0;i < bytes;i++)
                accum = (accum<<8) | in[i];
            break;
        default:
            break;
    }
    *out = accum;
    return 1;
}

// Read a binary value of the specified byte order from a file, storing it as
// a 64-bit unsigned integer.
static int ReadBin8(FILE *fp, const char *filename, const ByteOrderT order, uint64 *out)
{
    uint8 in [8];
    uint64 accum;
    uint i;

    if(fread(in, 1, 8, fp) != 8)
    {
        fprintf(stderr, "Error: Bad read from file '%s'.\n", filename);
        return 0;
    }
    accum = 0ULL;
    switch(order)
    {
        case BO_LITTLE:
            for(i = 0;i < 8;i++)
                accum = (accum<<8) | in[8 - i - 1];
            break;
        case BO_BIG:
            for(i = 0;i < 8;i++)
                accum = (accum<<8) | in[i];
            break;
        default:
            break;
    }
    *out = accum;
    return 1;
}

/* Read a binary value of the specified type, byte order, and byte size from
 * a file, converting it to a double.  For integer types, the significant
 * bits are used to normalize the result.  The sign of bits determines
 * whether they are padded toward the MSB (negative) or LSB (positive).
 * Floating-point types are not normalized.
 */
static int ReadBinAsDouble(FILE *fp, const char *filename, const ByteOrderT order, const ElementTypeT type, const uint bytes, const int bits, double *out)
{
    union {
        uint32 ui;
        int32 i;
        float f;
    } v4;
    union {
        uint64 ui;
        double f;
    } v8;

    *out = 0.0;
    if(bytes > 4)
    {
        if(!ReadBin8(fp, filename, order, &v8.ui))
            return 0;
        if(type == ET_FP)
            *out = v8.f;
    }
    else
    {
        if(!ReadBin4(fp, filename, order, bytes, &v4.ui))
            return 0;
        if(type == ET_FP)
            *out = v4.f;
        else
        {
            if(bits > 0)
                v4.ui >>= (8*bytes) - ((uint)bits);
            else
                v4.ui &= (0xFFFFFFFF >> (32+bits));

            if(v4.ui&(uint)(1<<(abs(bits)-1)))
                v4.ui |= (0xFFFFFFFF << abs (bits));
            *out = v4.i / (double)(1<<(abs(bits)-1));
        }
    }
    return 1;
}

/* Read an ascii value of the specified type from a file, converting it to a
 * double.  For integer types, the significant bits are used to normalize the
 * result.  The sign of the bits should always be positive.  This also skips
 * up to one separator character before the element itself.
 */
static int ReadAsciiAsDouble(TokenReaderT *tr, const char *filename, const ElementTypeT type, const uint bits, double *out)
{
    if(TrIsOperator(tr, ","))
        TrReadOperator(tr, ",");
    else if(TrIsOperator(tr, ":"))
        TrReadOperator(tr, ":");
    else if(TrIsOperator(tr, ";"))
        TrReadOperator(tr, ";");
    else if(TrIsOperator(tr, "|"))
        TrReadOperator(tr, "|");

    if(type == ET_FP)
    {
        if(!TrReadFloat(tr, -HUGE_VAL, HUGE_VAL, out))
        {
            fprintf(stderr, "Error: Bad read from file '%s'.\n", filename);
            return 0;
        }
    }
    else
    {
        int v;
        if(!TrReadInt(tr, -(1<<(bits-1)), (1<<(bits-1))-1, &v))
        {
            fprintf(stderr, "Error: Bad read from file '%s'.\n", filename);
            return 0;
        }
        *out = v / (double)((1<<(bits-1))-1);
    }
    return 1;
}

// Read the RIFF/RIFX WAVE format chunk from a file, validating it against
// the source parameters and data set metrics.
static int ReadWaveFormat(FILE *fp, const ByteOrderT order, const uint hrirRate, SourceRefT *src)
{
    uint32 fourCC, chunkSize;
    uint32 format, channels, rate, dummy, block, size, bits;

    chunkSize = 0;
    do {
        if (chunkSize > 0)
        fseek (fp, (long) chunkSize, SEEK_CUR);
        if(!ReadBin4(fp, src->mPath, BO_LITTLE, 4, &fourCC) ||
           !ReadBin4(fp, src->mPath, order, 4, &chunkSize))
        return 0;
    } while(fourCC != FOURCC_FMT);
    if(!ReadBin4(fp, src->mPath, order, 2, & format) ||
       !ReadBin4(fp, src->mPath, order, 2, & channels) ||
       !ReadBin4(fp, src->mPath, order, 4, & rate) ||
       !ReadBin4(fp, src->mPath, order, 4, & dummy) ||
       !ReadBin4(fp, src->mPath, order, 2, & block))
        return (0);
    block /= channels;
    if(chunkSize > 14)
    {
        if(!ReadBin4(fp, src->mPath, order, 2, &size))
            return 0;
        size /= 8;
        if(block > size)
            size = block;
    }
    else
        size = block;
    if(format == WAVE_FORMAT_EXTENSIBLE)
    {
        fseek(fp, 2, SEEK_CUR);
        if(!ReadBin4(fp, src->mPath, order, 2, &bits))
            return 0;
        if(bits == 0)
            bits = 8 * size;
        fseek(fp, 4, SEEK_CUR);
        if(!ReadBin4(fp, src->mPath, order, 2, &format))
            return 0;
        fseek(fp, (long)(chunkSize - 26), SEEK_CUR);
    }
    else
    {
        bits = 8 * size;
        if(chunkSize > 14)
            fseek(fp, (long)(chunkSize - 16), SEEK_CUR);
        else
            fseek(fp, (long)(chunkSize - 14), SEEK_CUR);
    }
    if(format != WAVE_FORMAT_PCM && format != WAVE_FORMAT_IEEE_FLOAT)
    {
        fprintf(stderr, "Error: Unsupported WAVE format in file '%s'.\n", src->mPath);
        return 0;
    }
    if(src->mChannel >= channels)
    {
        fprintf(stderr, "Error: Missing source channel in WAVE file '%s'.\n", src->mPath);
        return 0;
    }
    if(rate != hrirRate)
    {
        fprintf(stderr, "Error: Mismatched source sample rate in WAVE file '%s'.\n", src->mPath);
        return 0;
    }
    if(format == WAVE_FORMAT_PCM)
    {
        if(size < 2 || size > 4)
        {
            fprintf(stderr, "Error: Unsupported sample size in WAVE file '%s'.\n", src->mPath);
            return 0;
        }
        if(bits < 16 || bits > (8*size))
        {
            fprintf (stderr, "Error:  Bad significant bits in WAVE file '%s'.\n", src->mPath);
            return 0;
        }
        src->mType = ET_INT;
    }
    else
    {
        if(size != 4 && size != 8)
        {
            fprintf(stderr, "Error: Unsupported sample size in WAVE file '%s'.\n", src->mPath);
            return 0;
        }
        src->mType = ET_FP;
    }
    src->mSize = size;
    src->mBits = (int)bits;
    src->mSkip = channels;
    return 1;
}

// Read a RIFF/RIFX WAVE data chunk, converting all elements to doubles.
static int ReadWaveData(FILE *fp, const SourceRefT *src, const ByteOrderT order, const uint n, double *hrir)
{
    int pre, post, skip;
    uint i;

    pre = (int)(src->mSize * src->mChannel);
    post = (int)(src->mSize * (src->mSkip - src->mChannel - 1));
    skip = 0;
    for(i = 0;i < n;i++)
    {
        skip += pre;
        if(skip > 0)
            fseek(fp, skip, SEEK_CUR);
        if(!ReadBinAsDouble(fp, src->mPath, order, src->mType, src->mSize, src->mBits, &hrir[i]))
            return 0;
        skip = post;
    }
    if(skip > 0)
        fseek(fp, skip, SEEK_CUR);
    return 1;
}

// Read the RIFF/RIFX WAVE list or data chunk, converting all elements to
// doubles.
static int ReadWaveList(FILE *fp, const SourceRefT *src, const ByteOrderT order, const uint n, double *hrir)
{
    uint32 fourCC, chunkSize, listSize, count;
    uint block, skip, offset, i;
    double lastSample;

    for (;;) {
        if(!ReadBin4(fp, src->mPath, BO_LITTLE, 4, & fourCC) ||
           !ReadBin4(fp, src->mPath, order, 4, & chunkSize))
            return (0);

        if(fourCC == FOURCC_DATA)
        {
            block = src->mSize * src->mSkip;
            count = chunkSize / block;
            if(count < (src->mOffset + n))
            {
                fprintf(stderr, "Error: Bad read from file '%s'.\n", src->mPath);
                return 0;
            }
            fseek(fp, (long)(src->mOffset * block), SEEK_CUR);
            if(!ReadWaveData(fp, src, order, n, &hrir[0]))
                return 0;
            return 1;
        }
        else if(fourCC == FOURCC_LIST)
        {
            if(!ReadBin4(fp, src->mPath, BO_LITTLE, 4, &fourCC))
                return 0;
            chunkSize -= 4;
            if(fourCC == FOURCC_WAVL)
                break;
        }
        if(chunkSize > 0)
            fseek(fp, (long)chunkSize, SEEK_CUR);
    }
    listSize = chunkSize;
    block = src->mSize * src->mSkip;
    skip = src->mOffset;
    offset = 0;
    lastSample = 0.0;
    while(offset < n && listSize > 8)
    {
        if(!ReadBin4(fp, src->mPath, BO_LITTLE, 4, &fourCC) ||
           !ReadBin4(fp, src->mPath, order, 4, &chunkSize))
            return 0;
        listSize -= 8 + chunkSize;
        if(fourCC == FOURCC_DATA)
        {
            count = chunkSize / block;
            if(count > skip)
            {
                fseek(fp, (long)(skip * block), SEEK_CUR);
                chunkSize -= skip * block;
                count -= skip;
                skip = 0;
                if(count > (n - offset))
                    count = n - offset;
                if(!ReadWaveData(fp, src, order, count, &hrir[offset]))
                    return 0;
                chunkSize -= count * block;
                offset += count;
                lastSample = hrir [offset - 1];
            }
            else
            {
                skip -= count;
                count = 0;
            }
        }
        else if(fourCC == FOURCC_SLNT)
        {
            if(!ReadBin4(fp, src->mPath, order, 4, &count))
                return 0;
            chunkSize -= 4;
            if(count > skip)
            {
                count -= skip;
                skip = 0;
                if(count > (n - offset))
                    count = n - offset;
                for(i = 0; i < count; i ++)
                    hrir[offset + i] = lastSample;
                offset += count;
            }
            else
            {
                skip -= count;
                count = 0;
            }
        }
        if(chunkSize > 0)
            fseek(fp, (long)chunkSize, SEEK_CUR);
    }
    if(offset < n)
    {
        fprintf(stderr, "Error: Bad read from file '%s'.\n", src->mPath);
        return 0;
    }
    return 1;
}

// Load a source HRIR from a RIFF/RIFX WAVE file.
static int LoadWaveSource(FILE *fp, SourceRefT *src, const uint hrirRate, const uint n, double *hrir)
{
    uint32 fourCC, dummy;
    ByteOrderT order;

    if(!ReadBin4(fp, src->mPath, BO_LITTLE, 4, &fourCC) ||
       !ReadBin4(fp, src->mPath, BO_LITTLE, 4, &dummy))
        return 0;
    if(fourCC == FOURCC_RIFF)
        order = BO_LITTLE;
    else if(fourCC == FOURCC_RIFX)
        order = BO_BIG;
    else
    {
        fprintf(stderr, "Error: No RIFF/RIFX chunk in file '%s'.\n", src->mPath);
        return 0;
    }

    if(!ReadBin4(fp, src->mPath, BO_LITTLE, 4, &fourCC))
        return 0;
    if(fourCC != FOURCC_WAVE)
    {
        fprintf(stderr, "Error: Not a RIFF/RIFX WAVE file '%s'.\n", src->mPath);
        return 0;
    }
    if(!ReadWaveFormat(fp, order, hrirRate, src))
        return 0;
    if(!ReadWaveList(fp, src, order, n, hrir))
        return 0;
    return 1;
}

// Load a source HRIR from a binary file.
static int LoadBinarySource(FILE *fp, const SourceRefT *src, const ByteOrderT order, const uint n, double *hrir)
{
    uint i;

    fseek(fp, (long)src->mOffset, SEEK_SET);
    for(i = 0;i < n;i++)
    {
        if(!ReadBinAsDouble(fp, src->mPath, order, src->mType, src->mSize, src->mBits, &hrir[i]))
            return 0;
        if(src->mSkip > 0)
            fseek(fp, (long)src->mSkip, SEEK_CUR);
    }
    return 1;
}

// Load a source HRIR from an ASCII text file containing a list of elements
// separated by whitespace or common list operators (',', ';', ':', '|').
static int LoadAsciiSource(FILE *fp, const SourceRefT *src, const uint n, double *hrir)
{
    TokenReaderT tr;
    uint i, j;
    double dummy;

    TrSetup(fp, NULL, &tr);
    for(i = 0;i < src->mOffset;i++)
    {
        if(!ReadAsciiAsDouble(&tr, src->mPath, src->mType, (uint)src->mBits, &dummy))
            return (0);
    }
    for(i = 0;i < n;i++)
    {
        if(!ReadAsciiAsDouble(&tr, src->mPath, src->mType, (uint)src->mBits, &hrir[i]))
            return 0;
        for(j = 0;j < src->mSkip;j++)
        {
            if(!ReadAsciiAsDouble(&tr, src->mPath, src->mType, (uint)src->mBits, &dummy))
                return 0;
        }
    }
    return 1;
}

// Load a source HRIR from a supported file type.
static int LoadSource(SourceRefT *src, const uint hrirRate, const uint n, double *hrir)
{
    int result;
    FILE *fp;

    if (src->mFormat == SF_ASCII)
        fp = fopen(src->mPath, "r");
    else
        fp = fopen(src->mPath, "rb");
    if(fp == NULL)
    {
        fprintf(stderr, "Error: Could not open source file '%s'.\n", src->mPath);
        return 0;
    }
    if(src->mFormat == SF_WAVE)
        result = LoadWaveSource(fp, src, hrirRate, n, hrir);
    else if(src->mFormat == SF_BIN_LE)
        result = LoadBinarySource(fp, src, BO_LITTLE, n, hrir);
    else if(src->mFormat == SF_BIN_BE)
        result = LoadBinarySource(fp, src, BO_BIG, n, hrir);
    else
        result = LoadAsciiSource(fp, src, n, hrir);
    fclose(fp);
    return result;
}


/***************************
 *** File storage output ***
 ***************************/

// Write an ASCII string to a file.
static int WriteAscii(const char *out, FILE *fp, const char *filename)
{
    size_t len;

    len = strlen(out);
    if(fwrite(out, 1, len, fp) != len)
    {
        fclose(fp);
        fprintf(stderr, "Error: Bad write to file '%s'.\n", filename);
        return 0;
    }
    return 1;
}

// Write a binary value of the given byte order and byte size to a file,
// loading it from a 32-bit unsigned integer.
static int WriteBin4(const ByteOrderT order, const uint bytes, const uint32 in, FILE *fp, const char *filename)
{
    uint8 out[4];
    uint i;

    switch(order)
    {
        case BO_LITTLE:
            for(i = 0;i < bytes;i++)
                out[i] = (in>>(i*8)) & 0x000000FF;
            break;
        case BO_BIG:
            for(i = 0;i < bytes;i++)
                out[bytes - i - 1] = (in>>(i*8)) & 0x000000FF;
            break;
        default:
            break;
    }
    if(fwrite(out, 1, bytes, fp) != bytes)
    {
        fprintf(stderr, "Error: Bad write to file '%s'.\n", filename);
        return 0;
    }
    return 1;
}

// Store the OpenAL Soft HRTF data set.
static int StoreMhr(const HrirDataT *hData, const int experimental, const char *filename)
{
    uint e, step, end, n, j, i;
    uint dither_seed;
    FILE *fp;
    int v;

    if((fp=fopen(filename, "wb")) == NULL)
    {
        fprintf(stderr, "Error: Could not open MHR file '%s'.\n", filename);
        return 0;
    }
    if(!WriteAscii(experimental ? MHR_FORMAT_EXPERIMENTAL : MHR_FORMAT, fp, filename))
        return 0;
    if(!WriteBin4(BO_LITTLE, 4, (uint32)hData->mIrRate, fp, filename))
        return 0;
    if(experimental)
    {
        if(!WriteBin4(BO_LITTLE, 1, (uint32)hData->mSampleType, fp, filename))
            return 0;
        if(!WriteBin4(BO_LITTLE, 1, (uint32)hData->mChannelType, fp, filename))
            return 0;
    }
    if(!WriteBin4(BO_LITTLE, 1, (uint32)hData->mIrPoints, fp, filename))
        return 0;
    if(!WriteBin4(BO_LITTLE, 1, (uint32)hData->mEvCount, fp, filename))
        return 0;
    for(e = 0;e < hData->mEvCount;e++)
    {
        if(!WriteBin4(BO_LITTLE, 1, (uint32)hData->mAzCount[e], fp, filename))
            return 0;
    }
    step = hData->mIrSize;
    end = hData->mIrCount * step;
    n = hData->mIrPoints;
    dither_seed = 22222;
    for(j = 0;j < end;j += step)
    {
        const double scale = (!experimental || hData->mSampleType == ST_S16) ? 32767.0 :
                             ((hData->mSampleType == ST_S24) ? 8388607.0 : 0.0);
        const int bps = (!experimental || hData->mSampleType == ST_S16) ? 2 :
                        ((hData->mSampleType == ST_S24) ? 3 : 0);
        double out[MAX_TRUNCSIZE];
        for(i = 0;i < n;i++)
            out[i] = TpdfDither(scale * hData->mHrirs[j+i], &dither_seed);
        for(i = 0;i < n;i++)
        {
            v = (int)Clamp(out[i], -scale-1.0, scale);
            if(!WriteBin4(BO_LITTLE, bps, (uint32)v, fp, filename))
                return 0;
        }
    }
    for(j = 0;j < hData->mIrCount;j++)
    {
        v = (int)fmin(round(hData->mIrRate * hData->mHrtds[j]), MAX_HRTD);
        if(!WriteBin4(BO_LITTLE, 1, (uint32)v, fp, filename))
            return 0;
    }
    fclose(fp);
    return 1;
}


/***********************
 *** HRTF processing ***
 ***********************/

// Calculate the onset time of an HRIR and average it with any existing
// timing for its elevation and azimuth.
static void AverageHrirOnset(const double *hrir, const double f, const uint ei, const uint ai, const HrirDataT *hData)
{
    double mag;
    uint n, i, j;

    mag = 0.0;
    n = hData->mIrPoints;
    for(i = 0;i < n;i++)
        mag = fmax(fabs(hrir[i]), mag);
    mag *= 0.15;
    for(i = 0;i < n;i++)
    {
        if(fabs(hrir[i]) >= mag)
            break;
    }
    j = hData->mEvOffset[ei] + ai;
    hData->mHrtds[j] = Lerp(hData->mHrtds[j], ((double)i) / hData->mIrRate, f);
}

// Calculate the magnitude response of an HRIR and average it with any
// existing responses for its elevation and azimuth.
static void AverageHrirMagnitude(const double *hrir, const double f, const uint ei, const uint ai, const HrirDataT *hData)
{
    double *re, *im;
    uint n, m, i, j;

    n = hData->mFftSize;
    re = CreateArray(n);
    im = CreateArray(n);
    for(i = 0;i < hData->mIrPoints;i++)
    {
        re[i] = hrir[i];
        im[i] = 0.0;
    }
    for(;i < n;i++)
    {
        re[i] = 0.0;
        im[i] = 0.0;
    }
    FftForward(n, re, im, re, im);
    MagnitudeResponse(n, re, im, re);
    m = 1 + (n / 2);
    j = (hData->mEvOffset[ei] + ai) * hData->mIrSize;
    for(i = 0;i < m;i++)
        hData->mHrirs[j+i] = Lerp(hData->mHrirs[j+i], re[i], f);
    DestroyArray(im);
    DestroyArray(re);
}

/* Calculate the contribution of each HRIR to the diffuse-field average based
 * on the area of its surface patch.  All patches are centered at the HRIR
 * coordinates on the unit sphere and are measured by solid angle.
 */
static void CalculateDfWeights(const HrirDataT *hData, double *weights)
{
    double evs, sum, ev, up_ev, down_ev, solidAngle;
    uint ei;

    evs = 90.0 / (hData->mEvCount - 1);
    sum = 0.0;
    for(ei = hData->mEvStart;ei < hData->mEvCount;ei++)
    {
        // For each elevation, calculate the upper and lower limits of the
        // patch band.
        ev = -90.0 + (ei * 2.0 * evs);
        if(ei < (hData->mEvCount - 1))
            up_ev = (ev + evs) * M_PI / 180.0;
        else
            up_ev = M_PI / 2.0;
        if(ei > 0)
            down_ev = (ev - evs) * M_PI / 180.0;
        else
            down_ev = -M_PI / 2.0;
        // Calculate the area of the patch band.
        solidAngle = 2.0 * M_PI * (sin(up_ev) - sin(down_ev));
        // Each weight is the area of one patch.
        weights[ei] = solidAngle / hData->mAzCount [ei];
        // Sum the total surface area covered by the HRIRs.
        sum += solidAngle;
    }
    // Normalize the weights given the total surface coverage.
    for(ei = hData->mEvStart;ei < hData->mEvCount;ei++)
        weights[ei] /= sum;
}

/* Calculate the diffuse-field average from the given magnitude responses of
 * the HRIR set.  Weighting can be applied to compensate for the varying
 * surface area covered by each HRIR.  The final average can then be limited
 * by the specified magnitude range (in positive dB; 0.0 to skip).
 */
static void CalculateDiffuseFieldAverage(const HrirDataT *hData, const int weighted, const double limit, double *dfa)
{
    uint ei, ai, count, step, start, end, m, j, i;
    double *weights;

    weights = CreateArray(hData->mEvCount);
    if(weighted)
    {
        // Use coverage weighting to calculate the average.
        CalculateDfWeights(hData, weights);
    }
    else
    {
        // If coverage weighting is not used, the weights still need to be
        // averaged by the number of HRIRs.
        count = 0;
        for(ei = hData->mEvStart;ei < hData->mEvCount;ei++)
            count += hData->mAzCount [ei];
        for(ei = hData->mEvStart;ei < hData->mEvCount;ei++)
            weights[ei] = 1.0 / count;
    }
    ei = hData->mEvStart;
    ai = 0;
    step = hData->mIrSize;
    start = hData->mEvOffset[ei] * step;
    end = hData->mIrCount * step;
    m = 1 + (hData->mFftSize / 2);
    for(i = 0;i < m;i++)
        dfa[i] = 0.0;
    for(j = start;j < end;j += step)
    {
        // Get the weight for this HRIR's contribution.
        double weight = weights[ei];
        // Add this HRIR's weighted power average to the total.
        for(i = 0;i < m;i++)
            dfa[i] += weight * hData->mHrirs[j+i] * hData->mHrirs[j+i];
        // Determine the next weight to use.
        ai++;
        if(ai >= hData->mAzCount[ei])
        {
            ei++;
            ai = 0;
        }
    }
    // Finish the average calculation and keep it from being too small.
    for(i = 0;i < m;i++)
        dfa[i] = fmax(sqrt(dfa[i]), EPSILON);
    // Apply a limit to the magnitude range of the diffuse-field average if
    // desired.
    if(limit > 0.0)
        LimitMagnitudeResponse(hData->mFftSize, limit, dfa, dfa);
    DestroyArray(weights);
}

// Perform diffuse-field equalization on the magnitude responses of the HRIR
// set using the given average response.
static void DiffuseFieldEqualize(const double *dfa, const HrirDataT *hData)
{
    uint step, start, end, m, j, i;

    step = hData->mIrSize;
    start = hData->mEvOffset[hData->mEvStart] * step;
    end = hData->mIrCount * step;
    m = 1 + (hData->mFftSize / 2);
    for(j = start;j < end;j += step)
    {
        for(i = 0;i < m;i++)
            hData->mHrirs[j+i] /= dfa[i];
    }
}

// Perform minimum-phase reconstruction using the magnitude responses of the
// HRIR set.
static void ReconstructHrirs(const HrirDataT *hData)
{
    uint step, start, end, n, j, i;
    double *re, *im;

    step = hData->mIrSize;
    start = hData->mEvOffset[hData->mEvStart] * step;
    end = hData->mIrCount * step;
    n = hData->mFftSize;
    re = CreateArray(n);
    im = CreateArray(n);
    for(j = start;j < end;j += step)
    {
        MinimumPhase(n, &hData->mHrirs[j], re, im);
        FftInverse(n, re, im, re, im);
        for(i = 0;i < hData->mIrPoints;i++)
            hData->mHrirs[j+i] = re[i];
    }
    DestroyArray (im);
    DestroyArray (re);
}

// Resamples the HRIRs for use at the given sampling rate.
static void ResampleHrirs(const uint rate, HrirDataT *hData)
{
    uint n, step, start, end, j;
    ResamplerT rs;

    ResamplerSetup(&rs, hData->mIrRate, rate);
    n = hData->mIrPoints;
    step = hData->mIrSize;
    start = hData->mEvOffset[hData->mEvStart] * step;
    end = hData->mIrCount * step;
    for(j = start;j < end;j += step)
        ResamplerRun(&rs, n, &hData->mHrirs[j], n, &hData->mHrirs[j]);
    ResamplerClear(&rs);
    hData->mIrRate = rate;
}

/* Given an elevation index and an azimuth, calculate the indices of the two
 * HRIRs that bound the coordinate along with a factor for calculating the
 * continous HRIR using interpolation.
 */
static void CalcAzIndices(const HrirDataT *hData, const uint ei, const double az, uint *j0, uint *j1, double *jf)
{
    double af;
    uint ai;

    af = ((2.0*M_PI) + az) * hData->mAzCount[ei] / (2.0*M_PI);
    ai = ((uint)af) % hData->mAzCount[ei];
    af -= floor(af);

    *j0 = hData->mEvOffset[ei] + ai;
    *j1 = hData->mEvOffset[ei] + ((ai+1) % hData->mAzCount [ei]);
    *jf = af;
}

// Synthesize any missing onset timings at the bottom elevations.  This just
// blends between slightly exaggerated known onsets.  Not an accurate model.
static void SynthesizeOnsets(HrirDataT *hData)
{
    uint oi, e, a, j0, j1;
    double t, of, jf;

    oi = hData->mEvStart;
    t = 0.0;
    for(a = 0;a < hData->mAzCount[oi];a++)
        t += hData->mHrtds[hData->mEvOffset[oi] + a];
    hData->mHrtds[0] = 1.32e-4 + (t / hData->mAzCount[oi]);
    for(e = 1;e < hData->mEvStart;e++)
    {
        of = ((double)e) / hData->mEvStart;
        for(a = 0;a < hData->mAzCount[e];a++)
        {
            CalcAzIndices(hData, oi, a * 2.0 * M_PI / hData->mAzCount[e], &j0, &j1, &jf);
            hData->mHrtds[hData->mEvOffset[e] + a] = Lerp(hData->mHrtds[0], Lerp(hData->mHrtds[j0], hData->mHrtds[j1], jf), of);
        }
    }
}

/* Attempt to synthesize any missing HRIRs at the bottom elevations.  Right
 * now this just blends the lowest elevation HRIRs together and applies some
 * attenuation and high frequency damping.  It is a simple, if inaccurate
 * model.
 */
static void SynthesizeHrirs (HrirDataT *hData)
{
    uint oi, a, e, step, n, i, j;
    double lp[4], s0, s1;
    double of, b;
    uint j0, j1;
    double jf;

    if(hData->mEvStart <= 0)
        return;
    step = hData->mIrSize;
    oi = hData->mEvStart;
    n = hData->mIrPoints;
    for(i = 0;i < n;i++)
        hData->mHrirs[i] = 0.0;
    for(a = 0;a < hData->mAzCount[oi];a++)
    {
        j = (hData->mEvOffset[oi] + a) * step;
        for(i = 0;i < n;i++)
            hData->mHrirs[i] += hData->mHrirs[j+i] / hData->mAzCount[oi];
    }
    for(e = 1;e < hData->mEvStart;e++)
    {
        of = ((double)e) / hData->mEvStart;
        b = (1.0 - of) * (3.5e-6 * hData->mIrRate);
        for(a = 0;a < hData->mAzCount[e];a++)
        {
            j = (hData->mEvOffset[e] + a) * step;
            CalcAzIndices(hData, oi, a * 2.0 * M_PI / hData->mAzCount[e], &j0, &j1, &jf);
            j0 *= step;
            j1 *= step;
            lp[0] = 0.0;
            lp[1] = 0.0;
            lp[2] = 0.0;
            lp[3] = 0.0;
            for(i = 0;i < n;i++)
            {
                s0 = hData->mHrirs[i];
                s1 = Lerp(hData->mHrirs[j0+i], hData->mHrirs[j1+i], jf);
                s0 = Lerp(s0, s1, of);
                lp[0] = Lerp(s0, lp[0], b);
                lp[1] = Lerp(lp[0], lp[1], b);
                lp[2] = Lerp(lp[1], lp[2], b);
                lp[3] = Lerp(lp[2], lp[3], b);
                hData->mHrirs[j+i] = lp[3];
            }
        }
    }
    b = 3.5e-6 * hData->mIrRate;
    lp[0] = 0.0;
    lp[1] = 0.0;
    lp[2] = 0.0;
    lp[3] = 0.0;
    for(i = 0;i < n;i++)
    {
        s0 = hData->mHrirs[i];
        lp[0] = Lerp(s0, lp[0], b);
        lp[1] = Lerp(lp[0], lp[1], b);
        lp[2] = Lerp(lp[1], lp[2], b);
        lp[3] = Lerp(lp[2], lp[3], b);
        hData->mHrirs[i] = lp[3];
    }
    hData->mEvStart = 0;
}

// The following routines assume a full set of HRIRs for all elevations.

// Normalize the HRIR set and slightly attenuate the result.
static void NormalizeHrirs (const HrirDataT *hData)
{
    uint step, end, n, j, i;
    double maxLevel;

    step = hData->mIrSize;
    end = hData->mIrCount * step;
    n = hData->mIrPoints;
    maxLevel = 0.0;
    for(j = 0;j < end;j += step)
    {
        for(i = 0;i < n;i++)
            maxLevel = fmax(fabs(hData->mHrirs[j+i]), maxLevel);
    }
    maxLevel = 1.01 * maxLevel;
    for(j = 0;j < end;j += step)
    {
        for(i = 0;i < n;i++)
            hData->mHrirs[j+i] /= maxLevel;
    }
}

// Calculate the left-ear time delay using a spherical head model.
static double CalcLTD(const double ev, const double az, const double rad, const double dist)
{
    double azp, dlp, l, al;

    azp = asin(cos(ev) * sin(az));
    dlp = sqrt((dist*dist) + (rad*rad) + (2.0*dist*rad*sin(azp)));
    l = sqrt((dist*dist) - (rad*rad));
    al = (0.5 * M_PI) + azp;
    if(dlp > l)
        dlp = l + (rad * (al - acos(rad / dist)));
    return (dlp / 343.3);
}

// Calculate the effective head-related time delays for each minimum-phase
// HRIR.
static void CalculateHrtds (const HeadModelT model, const double radius, HrirDataT *hData)
{
    double minHrtd, maxHrtd;
    uint e, a, j;
    double t;

    minHrtd = 1000.0;
    maxHrtd = -1000.0;
    for(e = 0;e < hData->mEvCount;e++)
    {
        for(a = 0;a < hData->mAzCount[e];a++)
        {
            j = hData->mEvOffset[e] + a;
            if(model == HM_DATASET)
                t = hData->mHrtds[j] * radius / hData->mRadius;
            else
                t = CalcLTD((-90.0 + (e * 180.0 / (hData->mEvCount - 1))) * M_PI / 180.0,
                            (a * 360.0 / hData->mAzCount [e]) * M_PI / 180.0,
                            radius, hData->mDistance);
            hData->mHrtds[j] = t;
            maxHrtd = fmax(t, maxHrtd);
            minHrtd = fmin(t, minHrtd);
        }
    }
    maxHrtd -= minHrtd;
    for(j = 0;j < hData->mIrCount;j++)
        hData->mHrtds[j] -= minHrtd;
    hData->mMaxHrtd = maxHrtd;
}


// Process the data set definition to read and validate the data set metrics.
static int ProcessMetrics(TokenReaderT *tr, const uint fftSize, const uint truncSize, HrirDataT *hData)
{
    int hasRate = 0, hasPoints = 0, hasAzimuths = 0;
    int hasRadius = 0, hasDistance = 0;
    char ident[MAX_IDENT_LEN+1];
    uint line, col;
    double fpVal;
    uint points;
    int intVal;

    while(!(hasRate && hasPoints && hasAzimuths && hasRadius && hasDistance))
    {
        TrIndication(tr, & line, & col);
        if(!TrReadIdent(tr, MAX_IDENT_LEN, ident))
            return 0;
        if(strcasecmp(ident, "rate") == 0)
        {
            if(hasRate)
            {
                TrErrorAt(tr, line, col, "Redefinition of 'rate'.\n");
                return 0;
            }
            if(!TrReadOperator(tr, "="))
                return 0;
            if(!TrReadInt(tr, MIN_RATE, MAX_RATE, &intVal))
                return 0;
            hData->mIrRate = (uint)intVal;
            hasRate = 1;
        }
        else if(strcasecmp(ident, "points") == 0)
        {
            if (hasPoints) {
                TrErrorAt(tr, line, col, "Redefinition of 'points'.\n");
                return 0;
            }
            if(!TrReadOperator(tr, "="))
                return 0;
            TrIndication(tr, &line, &col);
            if(!TrReadInt(tr, MIN_POINTS, MAX_POINTS, &intVal))
                return 0;
            points = (uint)intVal;
            if(fftSize > 0 && points > fftSize)
            {
                TrErrorAt(tr, line, col, "Value exceeds the overridden FFT size.\n");
                return 0;
            }
            if(points < truncSize)
            {
                TrErrorAt(tr, line, col, "Value is below the truncation size.\n");
                return 0;
            }
            hData->mIrPoints = points;
            if(fftSize <= 0)
            {
                hData->mFftSize = DEFAULT_FFTSIZE;
                hData->mIrSize = 1 + (DEFAULT_FFTSIZE / 2);
            }
            else
            {
                hData->mFftSize = fftSize;
                hData->mIrSize = 1 + (fftSize / 2);
                if(points > hData->mIrSize)
                    hData->mIrSize = points;
            }
            hasPoints = 1;
        }
        else if(strcasecmp(ident, "azimuths") == 0)
        {
            if(hasAzimuths)
            {
                TrErrorAt(tr, line, col, "Redefinition of 'azimuths'.\n");
                return 0;
            }
            if(!TrReadOperator(tr, "="))
                return 0;
            hData->mIrCount = 0;
            hData->mEvCount = 0;
            hData->mEvOffset[0] = 0;
            for(;;)
            {
                if(!TrReadInt(tr, MIN_AZ_COUNT, MAX_AZ_COUNT, &intVal))
                    return 0;
                hData->mAzCount[hData->mEvCount] = (uint)intVal;
                hData->mIrCount += (uint)intVal;
                hData->mEvCount ++;
                if(!TrIsOperator(tr, ","))
                    break;
                if(hData->mEvCount >= MAX_EV_COUNT)
                {
                    TrError(tr, "Exceeded the maximum of %d elevations.\n", MAX_EV_COUNT);
                    return 0;
                }
                hData->mEvOffset[hData->mEvCount] = hData->mEvOffset[hData->mEvCount - 1] + ((uint)intVal);
                TrReadOperator(tr, ",");
            }
            if(hData->mEvCount < MIN_EV_COUNT)
            {
                TrErrorAt(tr, line, col, "Did not reach the minimum of %d azimuth counts.\n", MIN_EV_COUNT);
                return 0;
            }
            hasAzimuths = 1;
        }
        else if(strcasecmp(ident, "radius") == 0)
        {
            if(hasRadius)
            {
                TrErrorAt(tr, line, col, "Redefinition of 'radius'.\n");
                return 0;
            }
            if(!TrReadOperator(tr, "="))
                return 0;
            if(!TrReadFloat(tr, MIN_RADIUS, MAX_RADIUS, &fpVal))
                return 0;
            hData->mRadius = fpVal;
            hasRadius = 1;
        }
        else if(strcasecmp(ident, "distance") == 0)
        {
            if(hasDistance)
            {
                TrErrorAt(tr, line, col, "Redefinition of 'distance'.\n");
                return 0;
            }
            if(!TrReadOperator(tr, "="))
                return 0;
            if(!TrReadFloat(tr, MIN_DISTANCE, MAX_DISTANCE, & fpVal))
                return 0;
            hData->mDistance = fpVal;
            hasDistance = 1;
        }
        else
        {
            TrErrorAt(tr, line, col, "Expected a metric name.\n");
            return 0;
        }
        TrSkipWhitespace (tr);
    }
    return 1;
}

// Parse an index pair from the data set definition.
static int ReadIndexPair(TokenReaderT *tr, const HrirDataT *hData, uint *ei, uint *ai)
{
    int intVal;
    if(!TrReadInt(tr, 0, (int)hData->mEvCount, &intVal))
        return 0;
    *ei = (uint)intVal;
    if(!TrReadOperator(tr, ","))
        return 0;
    if(!TrReadInt(tr, 0, (int)hData->mAzCount[*ei], &intVal))
        return 0;
    *ai = (uint)intVal;
    return 1;
}

// Match the source format from a given identifier.
static SourceFormatT MatchSourceFormat(const char *ident)
{
    if(strcasecmp(ident, "wave") == 0)
        return SF_WAVE;
    if(strcasecmp(ident, "bin_le") == 0)
        return SF_BIN_LE;
    if(strcasecmp(ident, "bin_be") == 0)
        return SF_BIN_BE;
    if(strcasecmp(ident, "ascii") == 0)
        return SF_ASCII;
    return SF_NONE;
}

// Match the source element type from a given identifier.
static ElementTypeT MatchElementType(const char *ident)
{
    if(strcasecmp(ident, "int") == 0)
        return ET_INT;
    if(strcasecmp(ident, "fp") == 0)
        return ET_FP;
    return ET_NONE;
}

// Parse and validate a source reference from the data set definition.
static int ReadSourceRef(TokenReaderT *tr, SourceRefT *src)
{
    char ident[MAX_IDENT_LEN+1];
    uint line, col;
    int intVal;

    TrIndication(tr, &line, &col);
    if(!TrReadIdent(tr, MAX_IDENT_LEN, ident))
        return 0;
    src->mFormat = MatchSourceFormat(ident);
    if(src->mFormat == SF_NONE)
    {
        TrErrorAt(tr, line, col, "Expected a source format.\n");
        return 0;
    }
    if(!TrReadOperator(tr, "("))
        return 0;
    if(src->mFormat == SF_WAVE)
    {
        if(!TrReadInt(tr, 0, MAX_WAVE_CHANNELS, &intVal))
            return 0;
        src->mType = ET_NONE;
        src->mSize = 0;
        src->mBits = 0;
        src->mChannel = (uint)intVal;
        src->mSkip = 0;
    }
    else
    {
        TrIndication(tr, &line, &col);
        if(!TrReadIdent(tr, MAX_IDENT_LEN, ident))
            return 0;
        src->mType = MatchElementType(ident);
        if(src->mType == ET_NONE)
        {
            TrErrorAt(tr, line, col, "Expected a source element type.\n");
            return 0;
        }
        if(src->mFormat == SF_BIN_LE || src->mFormat == SF_BIN_BE)
        {
            if(!TrReadOperator(tr, ","))
                return 0;
            if(src->mType == ET_INT)
            {
                if(!TrReadInt(tr, MIN_BIN_SIZE, MAX_BIN_SIZE, &intVal))
                    return 0;
                src->mSize = (uint)intVal;
                if(!TrIsOperator(tr, ","))
                    src->mBits = (int)(8*src->mSize);
                else
                {
                    TrReadOperator(tr, ",");
                    TrIndication(tr, &line, &col);
                    if(!TrReadInt(tr, -2147483647-1, 2147483647, &intVal))
                        return 0;
                    if(abs(intVal) < MIN_BIN_BITS || ((uint)abs(intVal)) > (8*src->mSize))
                    {
                        TrErrorAt(tr, line, col, "Expected a value of (+/-) %d to %d.\n", MIN_BIN_BITS, 8*src->mSize);
                        return 0;
                    }
                    src->mBits = intVal;
                }
            }
            else
            {
                TrIndication(tr, &line, &col);
                if(!TrReadInt(tr, -2147483647-1, 2147483647, &intVal))
                    return 0;
                if(intVal != 4 && intVal != 8)
                {
                    TrErrorAt(tr, line, col, "Expected a value of 4 or 8.\n");
                    return 0;
                }
                src->mSize = (uint)intVal;
                src->mBits = 0;
            }
        }
        else if(src->mFormat == SF_ASCII && src->mType == ET_INT)
        {
            if(!TrReadOperator(tr, ","))
                return 0;
            if(!TrReadInt(tr, MIN_ASCII_BITS, MAX_ASCII_BITS, &intVal))
                return 0;
            src->mSize = 0;
            src->mBits = intVal;
        }
        else
        {
            src->mSize = 0;
            src->mBits = 0;
        }

        if(!TrIsOperator(tr, ";"))
            src->mSkip = 0;
        else
        {
            TrReadOperator(tr, ";");
            if(!TrReadInt (tr, 0, 0x7FFFFFFF, &intVal))
                return 0;
            src->mSkip = (uint)intVal;
        }
    }
    if(!TrReadOperator(tr, ")"))
        return 0;
    if(TrIsOperator(tr, "@"))
    {
        TrReadOperator(tr, "@");
        if(!TrReadInt(tr, 0, 0x7FFFFFFF, &intVal))
            return 0;
        src->mOffset = (uint)intVal;
    }
    else
        src->mOffset = 0;
    if(!TrReadOperator(tr, ":"))
        return 0;
    if(!TrReadString(tr, MAX_PATH_LEN, src->mPath))
        return 0;
    return 1;
}

// Process the list of sources in the data set definition.
static int ProcessSources(const HeadModelT model, TokenReaderT *tr, HrirDataT *hData)
{
    uint *setCount, *setFlag;
    uint line, col, ei, ai;
    SourceRefT src;
    double factor;
    double *hrir;

    setCount = (uint*)calloc(hData->mEvCount, sizeof(uint));
    setFlag = (uint*)calloc(hData->mIrCount, sizeof(uint));
    hrir = CreateArray(hData->mIrPoints);
    while(TrIsOperator(tr, "["))
    {
        TrIndication(tr, & line, & col);
        TrReadOperator(tr, "[");
        if(!ReadIndexPair(tr, hData, &ei, &ai))
            goto error;
        if(!TrReadOperator(tr, "]"))
            goto error;
        if(setFlag[hData->mEvOffset[ei] + ai])
        {
            TrErrorAt(tr, line, col, "Redefinition of source.\n");
            goto error;
        }
        if(!TrReadOperator(tr, "="))
            goto error;

        factor = 1.0;
        for(;;)
        {
            if(!ReadSourceRef(tr, &src))
                goto error;
            if(!LoadSource(&src, hData->mIrRate, hData->mIrPoints, hrir))
                goto error;

            if(model == HM_DATASET)
                AverageHrirOnset(hrir, 1.0 / factor, ei, ai, hData);
            AverageHrirMagnitude(hrir, 1.0 / factor, ei, ai, hData);
            factor += 1.0;
            if(!TrIsOperator(tr, "+"))
                break;
            TrReadOperator(tr, "+");
        }
        setFlag[hData->mEvOffset[ei] + ai] = 1;
        setCount[ei]++;
    }

    ei = 0;
    while(ei < hData->mEvCount && setCount[ei] < 1)
        ei++;
    if(ei < hData->mEvCount)
    {
        hData->mEvStart = ei;
        while(ei < hData->mEvCount && setCount[ei] == hData->mAzCount[ei])
            ei++;
        if(ei >= hData->mEvCount)
        {
            if(!TrLoad(tr))
            {
                DestroyArray(hrir);
                free(setFlag);
                free(setCount);
                return 1;
            }
            TrError(tr, "Errant data at end of source list.\n");
        }
        else
            TrError(tr, "Missing sources for elevation index %d.\n", ei);
    }
    else
        TrError(tr, "Missing source references.\n");

error:
    DestroyArray(hrir);
    free(setFlag);
    free(setCount);
    return 0;
}

/* Parse the data set definition and process the source data, storing the
 * resulting data set as desired.  If the input name is NULL it will read
 * from standard input.
 */
static int ProcessDefinition(const char *inName, const uint outRate, const uint fftSize, const int equalize, const int surface, const double limit, const uint truncSize, const HeadModelT model, const double radius, const OutputFormatT outFormat, const int experimental, const char *outName)
{
    char rateStr[8+1], expName[MAX_PATH_LEN];
    TokenReaderT tr;
    HrirDataT hData;
    double *dfa;
    FILE *fp;

    hData.mIrRate = 0;
    hData.mSampleType = ST_S24;
    hData.mChannelType = CT_LEFTONLY;
    hData.mIrPoints = 0;
    hData.mFftSize = 0;
    hData.mIrSize = 0;
    hData.mIrCount = 0;
    hData.mEvCount = 0;
    hData.mRadius = 0;
    hData.mDistance = 0;
    fprintf(stdout, "Reading HRIR definition...\n");
    if(inName != NULL)
    {
        fp = fopen(inName, "r");
        if(fp == NULL)
        {
            fprintf(stderr, "Error: Could not open definition file '%s'\n", inName);
            return 0;
        }
        TrSetup(fp, inName, &tr);
    }
    else
    {
        fp = stdin;
        TrSetup(fp, "<stdin>", &tr);
    }
    if(!ProcessMetrics(&tr, fftSize, truncSize, &hData))
    {
        if(inName != NULL)
            fclose(fp);
        return 0;
    }
    hData.mHrirs = CreateArray(hData.mIrCount * hData.mIrSize);
    hData.mHrtds = CreateArray(hData.mIrCount);
    if(!ProcessSources(model, &tr, &hData))
    {
        DestroyArray(hData.mHrtds);
        DestroyArray(hData.mHrirs);
        if(inName != NULL)
            fclose(fp);
        return 0;
    }
    if(inName != NULL)
        fclose(fp);
    if(equalize)
    {
        dfa = CreateArray(1 + (hData.mFftSize/2));
        fprintf(stdout, "Calculating diffuse-field average...\n");
        CalculateDiffuseFieldAverage(&hData, surface, limit, dfa);
        fprintf(stdout, "Performing diffuse-field equalization...\n");
        DiffuseFieldEqualize(dfa, &hData);
        DestroyArray(dfa);
    }
    fprintf(stdout, "Performing minimum phase reconstruction...\n");
    ReconstructHrirs(&hData);
    if(outRate != 0 && outRate != hData.mIrRate)
    {
        fprintf(stdout, "Resampling HRIRs...\n");
        ResampleHrirs(outRate, &hData);
    }
    fprintf(stdout, "Truncating minimum-phase HRIRs...\n");
    hData.mIrPoints = truncSize;
    fprintf(stdout, "Synthesizing missing elevations...\n");
    if(model == HM_DATASET)
        SynthesizeOnsets(&hData);
    SynthesizeHrirs(&hData);
    fprintf(stdout, "Normalizing final HRIRs...\n");
    NormalizeHrirs(&hData);
    fprintf(stdout, "Calculating impulse delays...\n");
    CalculateHrtds(model, (radius > DEFAULT_CUSTOM_RADIUS) ? radius : hData.mRadius, &hData);
    snprintf(rateStr, 8, "%u", hData.mIrRate);
    StrSubst(outName, "%r", rateStr, MAX_PATH_LEN, expName);
    switch(outFormat)
    {
        case OF_MHR:
            fprintf(stdout, "Creating MHR data set file...\n");
            if(!StoreMhr(&hData, experimental, expName))
            {
                DestroyArray(hData.mHrtds);
                DestroyArray(hData.mHrirs);
                return 0;
            }
            break;
        default:
            break;
    }
    DestroyArray(hData.mHrtds);
    DestroyArray(hData.mHrirs);
    return 1;
}

static void PrintHelp(const char *argv0, FILE *ofile)
{
    fprintf(ofile, "Usage:  %s <command> [<option>...]\n\n", argv0);
    fprintf(ofile, "Commands:\n");
    fprintf(ofile, " -m, --make-mhr  Makes an OpenAL Soft compatible HRTF data set.\n");
    fprintf(ofile, "                 Defaults output to: ./oalsoft_hrtf_%%r.mhr\n");
    fprintf(ofile, " -h, --help      Displays this help information.\n\n");
    fprintf(ofile, "Options:\n");
    fprintf(ofile, " -r=<rate>       Change the data set sample rate to the specified value and\n");
    fprintf(ofile, "                 resample the HRIRs accordingly.\n");
    fprintf(ofile, " -f=<points>     Override the FFT window size (default: %u).\n", DEFAULT_FFTSIZE);
    fprintf(ofile, " -e={on|off}     Toggle diffuse-field equalization (default: %s).\n", (DEFAULT_EQUALIZE ? "on" : "off"));
    fprintf(ofile, " -s={on|off}     Toggle surface-weighted diffuse-field average (default: %s).\n", (DEFAULT_SURFACE ? "on" : "off"));
    fprintf(ofile, " -l={<dB>|none}  Specify a limit to the magnitude range of the diffuse-field\n");
    fprintf(ofile, "                 average (default: %.2f).\n", DEFAULT_LIMIT);
    fprintf(ofile, " -w=<points>     Specify the size of the truncation window that's applied\n");
    fprintf(ofile, "                 after minimum-phase reconstruction (default: %u).\n", DEFAULT_TRUNCSIZE);
    fprintf(ofile, " -d={dataset|    Specify the model used for calculating the head-delay timing\n");
    fprintf(ofile, "     sphere}     values (default: %s).\n", ((DEFAULT_HEAD_MODEL == HM_DATASET) ? "dataset" : "sphere"));
    fprintf(ofile, " -c=<size>       Use a customized head radius measured ear-to-ear in meters.\n");
    fprintf(ofile, " -i=<filename>   Specify an HRIR definition file to use (defaults to stdin).\n");
    fprintf(ofile, " -o=<filename>   Specify an output file.  Overrides command-selected default.\n");
    fprintf(ofile, "                 Use of '%%r' will be substituted with the data set sample rate.\n");
}

// Standard command line dispatch.
int main(const int argc, const char *argv[])
{
    const char *inName = NULL, *outName = NULL;
    OutputFormatT outFormat;
    uint outRate, fftSize;
    int equalize, surface;
    int experimental;
    char *end = NULL;
    HeadModelT model;
    uint truncSize;
    double radius;
    double limit;
    int argi;

    if(argc < 2 || strcmp(argv[1], "--help") == 0 || strcmp(argv[1], "-h") == 0)
    {
        fprintf(stdout, "HRTF Processing and Composition Utility\n\n");
        PrintHelp(argv[0], stdout);
        return 0;
    }

    if(strcmp(argv[1], "--make-mhr") == 0 || strcmp(argv[1], "-m") == 0)
    {
        outName = "./oalsoft_hrtf_%r.mhr";
        outFormat = OF_MHR;
    }
    else
    {
        fprintf(stderr, "Error: Invalid command '%s'.\n\n", argv[1]);
        PrintHelp(argv[0], stderr);
        return -1;
    }

    outRate = 0;
    fftSize = 0;
    equalize = DEFAULT_EQUALIZE;
    surface = DEFAULT_SURFACE;
    limit = DEFAULT_LIMIT;
    truncSize = DEFAULT_TRUNCSIZE;
    model = DEFAULT_HEAD_MODEL;
    radius = DEFAULT_CUSTOM_RADIUS;
    experimental = 0;

    argi = 2;
    while(argi < argc)
    {
        if(strncmp(argv[argi], "-r=", 3) == 0)
        {
            outRate = strtoul(&argv[argi][3], &end, 10);
            if(end[0] != '\0' || outRate < MIN_RATE || outRate > MAX_RATE)
            {
                fprintf(stderr, "Error:  Expected a value from %u to %u for '-r'.\n", MIN_RATE, MAX_RATE);
                return -1;
            }
        }
        else if(strncmp(argv[argi], "-f=", 3) == 0)
        {
            fftSize = strtoul(&argv[argi][3], &end, 10);
            if(end[0] != '\0' || (fftSize&(fftSize-1)) || fftSize < MIN_FFTSIZE || fftSize > MAX_FFTSIZE)
            {
                fprintf(stderr, "Error:  Expected a power-of-two value from %u to %u for '-f'.\n", MIN_FFTSIZE, MAX_FFTSIZE);
                return -1;
            }
        }
        else if(strncmp(argv[argi], "-e=", 3) == 0)
        {
            if(strcmp(&argv[argi][3], "on") == 0)
                equalize = 1;
            else if(strcmp(&argv[argi][3], "off") == 0)
                equalize = 0;
            else
            {
                fprintf(stderr, "Error:  Expected 'on' or 'off' for '-e'.\n");
                return -1;
            }
        }
        else if(strncmp(argv[argi], "-s=", 3) == 0)
        {
            if(strcmp(&argv[argi][3], "on") == 0)
                surface = 1;
            else if(strcmp(&argv[argi][3], "off") == 0)
                surface = 0;
            else
            {
                fprintf(stderr, "Error:  Expected 'on' or 'off' for '-s'.\n");
                return -1;
            }
        }
        else if(strncmp(argv[argi], "-l=", 3) == 0)
        {
            if(strcmp(&argv[argi][3], "none") == 0)
                limit = 0.0;
            else
            {
                limit = strtod(&argv[argi] [3], &end);
                if(end[0] != '\0' || limit < MIN_LIMIT || limit > MAX_LIMIT)
                {
                    fprintf(stderr, "Error:  Expected 'none' or a value from %.2f to %.2f for '-l'.\n", MIN_LIMIT, MAX_LIMIT);
                    return -1;
                }
            }
        }
        else if(strncmp(argv[argi], "-w=", 3) == 0)
        {
            truncSize = strtoul(&argv[argi][3], &end, 10);
            if(end[0] != '\0' || truncSize < MIN_TRUNCSIZE || truncSize > MAX_TRUNCSIZE || (truncSize%MOD_TRUNCSIZE))
            {
                fprintf(stderr, "Error:  Expected a value from %u to %u in multiples of %u for '-w'.\n", MIN_TRUNCSIZE, MAX_TRUNCSIZE, MOD_TRUNCSIZE);
                return -1;
            }
        }
        else if(strncmp(argv[argi], "-d=", 3) == 0)
        {
            if(strcmp(&argv[argi][3], "dataset") == 0)
                model = HM_DATASET;
            else if(strcmp(&argv[argi][3], "sphere") == 0)
                model = HM_SPHERE;
            else
            {
                fprintf(stderr, "Error:  Expected 'dataset' or 'sphere' for '-d'.\n");
                return -1;
            }
        }
        else if(strncmp(argv[argi], "-c=", 3) == 0)
        {
            radius = strtod(&argv[argi][3], &end);
            if(end[0] != '\0' || radius < MIN_CUSTOM_RADIUS || radius > MAX_CUSTOM_RADIUS)
            {
                fprintf(stderr, "Error:  Expected a value from %.2f to %.2f for '-c'.\n", MIN_CUSTOM_RADIUS, MAX_CUSTOM_RADIUS);
                return -1;
            }
        }
        else if(strncmp(argv[argi], "-i=", 3) == 0)
            inName = &argv[argi][3];
        else if(strncmp(argv[argi], "-o=", 3) == 0)
            outName = &argv[argi][3];
        else if(strcmp(argv[argi], "--experimental") == 0)
            experimental = 1;
        else
        {
            fprintf(stderr, "Error:  Invalid option '%s'.\n", argv[argi]);
            return -1;
        }
        argi++;
    }
    if(!ProcessDefinition(inName, outRate, fftSize, equalize, surface, limit,
                          truncSize, model, radius, outFormat, experimental,
                          outName))
        return -1;
    fprintf(stdout, "Operation completed.\n");
    return 0;
}