/* * Generates a synthetic stereo sound * NOTE: no floats are used to guaranty a bit exact output. */#include <stdlib.h>#include <stdio.h>#define NB_CHANNELS 2#define FE 44100static unsigned int myrnd(unsigned int *seed_ptr, int n){    unsigned int seed, val;    seed = *seed_ptr;    seed = (seed * 314159) + 1;    if (n == 256) {        val = seed >> 24;    } else {        val = seed % n;    }    *seed_ptr = seed;    return val;}#define FRAC_BITS 16#define FRAC_ONE (1 << FRAC_BITS)#define COS_TABLE_BITS 7/* integer cosinus */static const unsigned short cos_table[(1 << COS_TABLE_BITS) + 2] = { 0x8000, 0x7ffe, 0x7ff6, 0x7fea, 0x7fd9, 0x7fc2, 0x7fa7, 0x7f87, 0x7f62, 0x7f38, 0x7f0a, 0x7ed6, 0x7e9d, 0x7e60, 0x7e1e, 0x7dd6, 0x7d8a, 0x7d3a, 0x7ce4, 0x7c89, 0x7c2a, 0x7bc6, 0x7b5d, 0x7aef, 0x7a7d, 0x7a06, 0x798a, 0x790a, 0x7885, 0x77fb, 0x776c, 0x76d9, 0x7642, 0x75a6, 0x7505, 0x7460, 0x73b6, 0x7308, 0x7255, 0x719e, 0x70e3, 0x7023, 0x6f5f, 0x6e97, 0x6dca, 0x6cf9, 0x6c24, 0x6b4b, 0x6a6e, 0x698c, 0x68a7, 0x67bd, 0x66d0, 0x65de, 0x64e9, 0x63ef, 0x62f2, 0x61f1, 0x60ec, 0x5fe4, 0x5ed7, 0x5dc8, 0x5cb4, 0x5b9d, 0x5a82, 0x5964, 0x5843, 0x571e, 0x55f6, 0x54ca, 0x539b, 0x5269, 0x5134, 0x4ffb, 0x4ec0, 0x4d81, 0x4c40, 0x4afb, 0x49b4, 0x486a, 0x471d, 0x45cd, 0x447b, 0x4326, 0x41ce, 0x4074, 0x3f17, 0x3db8, 0x3c57, 0x3af3, 0x398d, 0x3825, 0x36ba, 0x354e, 0x33df, 0x326e, 0x30fc, 0x2f87, 0x2e11, 0x2c99, 0x2b1f, 0x29a4, 0x2827, 0x26a8, 0x2528, 0x23a7, 0x2224, 0x209f, 0x1f1a, 0x1d93, 0x1c0c, 0x1a83, 0x18f9, 0x176e, 0x15e2, 0x1455, 0x12c8, 0x113a, 0x0fab, 0x0e1c, 0x0c8c, 0x0afb, 0x096b, 0x07d9, 0x0648, 0x04b6, 0x0324, 0x0192, 0x0000, 0x0000,};#define CSHIFT (FRAC_BITS - COS_TABLE_BITS - 2)static int int_cos(int a){    int neg, v, f;    const unsigned short *p;    a = a & (FRAC_ONE - 1); /* modulo 2 * pi */    if (a >= (FRAC_ONE / 2))        a = FRAC_ONE - a;    neg = 0;    if (a > (FRAC_ONE / 4)) {        neg = -1;        a = (FRAC_ONE / 2) - a;    }    p = cos_table + (a >> CSHIFT);    /* linear interpolation */    f = a & ((1 << CSHIFT) - 1);    v = p[0] + (((p[1] - p[0]) * f + (1 << (CSHIFT - 1))) >> CSHIFT);    v = (v ^ neg) - neg;    v = v << (FRAC_BITS - 15);    return v;}FILE *outfile;void put_sample(int v){    fputc(v & 0xff, outfile);    fputc((v >> 8) & 0xff, outfile);}int main(int argc, char **argv){    int i, a, v, j, f, amp, ampa;    unsigned int seed = 1;    int tabf1[NB_CHANNELS], tabf2[NB_CHANNELS];    int taba[NB_CHANNELS];    if (argc != 2) {        printf("usage: %s file\n"               "generate a test raw 16 bit stereo audio stream\n", argv[0]);        exit(1);    }        outfile = fopen(argv[1], "wb");    if (!outfile) {        perror(argv[1]);        return 1;    }    /* 1 second of single freq sinus at 1000 Hz */    a = 0;    for(i=0;i<1 * FE;i++) {        v = (int_cos(a) * 10000) >> FRAC_BITS;        for(j=0;j<NB_CHANNELS;j++)            put_sample(v);        a += (1000 * FRAC_ONE) / FE;    }    /* 1 second of varing frequency between 100 and 10000 Hz */    a = 0;    for(i=0;i<1 * FE;i++) {        v = (int_cos(a) * 10000) >> FRAC_BITS;        for(j=0;j<NB_CHANNELS;j++)            put_sample(v);        f = 100 + (((10000 - 100) * i) / FE);        a += (f * FRAC_ONE) / FE;    }        /* 0.5 second of low amplitude white noise */    for(i=0;i<FE / 2;i++) {        v = myrnd(&seed, 20000) - 10000;        for(j=0;j<NB_CHANNELS;j++)            put_sample(v);    }    /* 0.5 second of high amplitude white noise */    for(i=0;i<FE / 2;i++) {        v = myrnd(&seed, 65535) - 32768;        for(j=0;j<NB_CHANNELS;j++)            put_sample(v);    }    /* stereo : 2 unrelated ramps */    for(j=0;j<NB_CHANNELS;j++) {        taba[j] = 0;        tabf1[j] = 100 + myrnd(&seed, 5000);        tabf2[j] = 100 + myrnd(&seed, 5000);    }    for(i=0;i<1 * FE;i++) {        for(j=0;j<NB_CHANNELS;j++) {            v = (int_cos(taba[j]) * 10000) >> FRAC_BITS;            put_sample(v);            f = tabf1[j] + (((tabf2[j] - tabf1[j]) * i) / FE);            taba[j] += (f * FRAC_ONE) / FE;        }    }        /* stereo 500 Hz with varying volume */    a = 0;    ampa = 0;    for(i=0;i<2 * FE;i++) {        for(j=0;j<NB_CHANNELS;j++) {            amp = ((FRAC_ONE + int_cos(ampa)) * 5000) >> FRAC_BITS;            if (j & 1)                amp = 10000 - amp;            v = (int_cos(a) * amp) >> FRAC_BITS;            put_sample(v);            a += (500 * FRAC_ONE) / FE;            ampa += (2 * FRAC_ONE) / FE;        }    }    fclose(outfile);    return 0;}