Chris@69: /* Copyright (c) 2007-2008 CSIRO
Chris@69:    Copyright (c) 2007-2009 Xiph.Org Foundation
Chris@69:    Written by Jean-Marc Valin */
Chris@69: /**
Chris@69:    @file pitch.c
Chris@69:    @brief Pitch analysis
Chris@69:  */
Chris@69: 
Chris@69: /*
Chris@69:    Redistribution and use in source and binary forms, with or without
Chris@69:    modification, are permitted provided that the following conditions
Chris@69:    are met:
Chris@69: 
Chris@69:    - Redistributions of source code must retain the above copyright
Chris@69:    notice, this list of conditions and the following disclaimer.
Chris@69: 
Chris@69:    - Redistributions in binary form must reproduce the above copyright
Chris@69:    notice, this list of conditions and the following disclaimer in the
Chris@69:    documentation and/or other materials provided with the distribution.
Chris@69: 
Chris@69:    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
Chris@69:    ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
Chris@69:    LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
Chris@69:    A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
Chris@69:    OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
Chris@69:    EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
Chris@69:    PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
Chris@69:    PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
Chris@69:    LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
Chris@69:    NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
Chris@69:    SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
Chris@69: */
Chris@69: 
Chris@69: #ifdef HAVE_CONFIG_H
Chris@69: #include "config.h"
Chris@69: #endif
Chris@69: 
Chris@69: #include "pitch.h"
Chris@69: #include "os_support.h"
Chris@69: #include "modes.h"
Chris@69: #include "stack_alloc.h"
Chris@69: #include "mathops.h"
Chris@69: #include "celt_lpc.h"
Chris@69: 
Chris@69: static void find_best_pitch(opus_val32 *xcorr, opus_val16 *y, int len,
Chris@69:                             int max_pitch, int *best_pitch
Chris@69: #ifdef FIXED_POINT
Chris@69:                             , int yshift, opus_val32 maxcorr
Chris@69: #endif
Chris@69:                             )
Chris@69: {
Chris@69:    int i, j;
Chris@69:    opus_val32 Syy=1;
Chris@69:    opus_val16 best_num[2];
Chris@69:    opus_val32 best_den[2];
Chris@69: #ifdef FIXED_POINT
Chris@69:    int xshift;
Chris@69: 
Chris@69:    xshift = celt_ilog2(maxcorr)-14;
Chris@69: #endif
Chris@69: 
Chris@69:    best_num[0] = -1;
Chris@69:    best_num[1] = -1;
Chris@69:    best_den[0] = 0;
Chris@69:    best_den[1] = 0;
Chris@69:    best_pitch[0] = 0;
Chris@69:    best_pitch[1] = 1;
Chris@69:    for (j=0;j<len;j++)
Chris@69:       Syy = ADD32(Syy, SHR32(MULT16_16(y[j],y[j]), yshift));
Chris@69:    for (i=0;i<max_pitch;i++)
Chris@69:    {
Chris@69:       if (xcorr[i]>0)
Chris@69:       {
Chris@69:          opus_val16 num;
Chris@69:          opus_val32 xcorr16;
Chris@69:          xcorr16 = EXTRACT16(VSHR32(xcorr[i], xshift));
Chris@69: #ifndef FIXED_POINT
Chris@69:          /* Considering the range of xcorr16, this should avoid both underflows
Chris@69:             and overflows (inf) when squaring xcorr16 */
Chris@69:          xcorr16 *= 1e-12f;
Chris@69: #endif
Chris@69:          num = MULT16_16_Q15(xcorr16,xcorr16);
Chris@69:          if (MULT16_32_Q15(num,best_den[1]) > MULT16_32_Q15(best_num[1],Syy))
Chris@69:          {
Chris@69:             if (MULT16_32_Q15(num,best_den[0]) > MULT16_32_Q15(best_num[0],Syy))
Chris@69:             {
Chris@69:                best_num[1] = best_num[0];
Chris@69:                best_den[1] = best_den[0];
Chris@69:                best_pitch[1] = best_pitch[0];
Chris@69:                best_num[0] = num;
Chris@69:                best_den[0] = Syy;
Chris@69:                best_pitch[0] = i;
Chris@69:             } else {
Chris@69:                best_num[1] = num;
Chris@69:                best_den[1] = Syy;
Chris@69:                best_pitch[1] = i;
Chris@69:             }
Chris@69:          }
Chris@69:       }
Chris@69:       Syy += SHR32(MULT16_16(y[i+len],y[i+len]),yshift) - SHR32(MULT16_16(y[i],y[i]),yshift);
Chris@69:       Syy = MAX32(1, Syy);
Chris@69:    }
Chris@69: }
Chris@69: 
Chris@69: static void celt_fir5(opus_val16 *x,
Chris@69:          const opus_val16 *num,
Chris@69:          int N)
Chris@69: {
Chris@69:    int i;
Chris@69:    opus_val16 num0, num1, num2, num3, num4;
Chris@69:    opus_val32 mem0, mem1, mem2, mem3, mem4;
Chris@69:    num0=num[0];
Chris@69:    num1=num[1];
Chris@69:    num2=num[2];
Chris@69:    num3=num[3];
Chris@69:    num4=num[4];
Chris@69:    mem0=0;
Chris@69:    mem1=0;
Chris@69:    mem2=0;
Chris@69:    mem3=0;
Chris@69:    mem4=0;
Chris@69:    for (i=0;i<N;i++)
Chris@69:    {
Chris@69:       opus_val32 sum = SHL32(EXTEND32(x[i]), SIG_SHIFT);
Chris@69:       sum = MAC16_16(sum,num0,mem0);
Chris@69:       sum = MAC16_16(sum,num1,mem1);
Chris@69:       sum = MAC16_16(sum,num2,mem2);
Chris@69:       sum = MAC16_16(sum,num3,mem3);
Chris@69:       sum = MAC16_16(sum,num4,mem4);
Chris@69:       mem4 = mem3;
Chris@69:       mem3 = mem2;
Chris@69:       mem2 = mem1;
Chris@69:       mem1 = mem0;
Chris@69:       mem0 = x[i];
Chris@69:       x[i] = ROUND16(sum, SIG_SHIFT);
Chris@69:    }
Chris@69: }
Chris@69: 
Chris@69: 
Chris@69: void pitch_downsample(celt_sig * OPUS_RESTRICT x[], opus_val16 * OPUS_RESTRICT x_lp,
Chris@69:       int len, int C, int arch)
Chris@69: {
Chris@69:    int i;
Chris@69:    opus_val32 ac[5];
Chris@69:    opus_val16 tmp=Q15ONE;
Chris@69:    opus_val16 lpc[4];
Chris@69:    opus_val16 lpc2[5];
Chris@69:    opus_val16 c1 = QCONST16(.8f,15);
Chris@69: #ifdef FIXED_POINT
Chris@69:    int shift;
Chris@69:    opus_val32 maxabs = celt_maxabs32(x[0], len);
Chris@69:    if (C==2)
Chris@69:    {
Chris@69:       opus_val32 maxabs_1 = celt_maxabs32(x[1], len);
Chris@69:       maxabs = MAX32(maxabs, maxabs_1);
Chris@69:    }
Chris@69:    if (maxabs<1)
Chris@69:       maxabs=1;
Chris@69:    shift = celt_ilog2(maxabs)-10;
Chris@69:    if (shift<0)
Chris@69:       shift=0;
Chris@69:    if (C==2)
Chris@69:       shift++;
Chris@69: #endif
Chris@69:    for (i=1;i<len>>1;i++)
Chris@69:       x_lp[i] = SHR32(HALF32(HALF32(x[0][(2*i-1)]+x[0][(2*i+1)])+x[0][2*i]), shift);
Chris@69:    x_lp[0] = SHR32(HALF32(HALF32(x[0][1])+x[0][0]), shift);
Chris@69:    if (C==2)
Chris@69:    {
Chris@69:       for (i=1;i<len>>1;i++)
Chris@69:          x_lp[i] += SHR32(HALF32(HALF32(x[1][(2*i-1)]+x[1][(2*i+1)])+x[1][2*i]), shift);
Chris@69:       x_lp[0] += SHR32(HALF32(HALF32(x[1][1])+x[1][0]), shift);
Chris@69:    }
Chris@69: 
Chris@69:    _celt_autocorr(x_lp, ac, NULL, 0,
Chris@69:                   4, len>>1, arch);
Chris@69: 
Chris@69:    /* Noise floor -40 dB */
Chris@69: #ifdef FIXED_POINT
Chris@69:    ac[0] += SHR32(ac[0],13);
Chris@69: #else
Chris@69:    ac[0] *= 1.0001f;
Chris@69: #endif
Chris@69:    /* Lag windowing */
Chris@69:    for (i=1;i<=4;i++)
Chris@69:    {
Chris@69:       /*ac[i] *= exp(-.5*(2*M_PI*.002*i)*(2*M_PI*.002*i));*/
Chris@69: #ifdef FIXED_POINT
Chris@69:       ac[i] -= MULT16_32_Q15(2*i*i, ac[i]);
Chris@69: #else
Chris@69:       ac[i] -= ac[i]*(.008f*i)*(.008f*i);
Chris@69: #endif
Chris@69:    }
Chris@69: 
Chris@69:    _celt_lpc(lpc, ac, 4);
Chris@69:    for (i=0;i<4;i++)
Chris@69:    {
Chris@69:       tmp = MULT16_16_Q15(QCONST16(.9f,15), tmp);
Chris@69:       lpc[i] = MULT16_16_Q15(lpc[i], tmp);
Chris@69:    }
Chris@69:    /* Add a zero */
Chris@69:    lpc2[0] = lpc[0] + QCONST16(.8f,SIG_SHIFT);
Chris@69:    lpc2[1] = lpc[1] + MULT16_16_Q15(c1,lpc[0]);
Chris@69:    lpc2[2] = lpc[2] + MULT16_16_Q15(c1,lpc[1]);
Chris@69:    lpc2[3] = lpc[3] + MULT16_16_Q15(c1,lpc[2]);
Chris@69:    lpc2[4] = MULT16_16_Q15(c1,lpc[3]);
Chris@69:    celt_fir5(x_lp, lpc2, len>>1);
Chris@69: }
Chris@69: 
Chris@69: /* Pure C implementation. */
Chris@69: #ifdef FIXED_POINT
Chris@69: opus_val32
Chris@69: #else
Chris@69: void
Chris@69: #endif
Chris@69: celt_pitch_xcorr_c(const opus_val16 *_x, const opus_val16 *_y,
Chris@69:       opus_val32 *xcorr, int len, int max_pitch, int arch)
Chris@69: {
Chris@69: 
Chris@69: #if 0 /* This is a simple version of the pitch correlation that should work
Chris@69:          well on DSPs like Blackfin and TI C5x/C6x */
Chris@69:    int i, j;
Chris@69: #ifdef FIXED_POINT
Chris@69:    opus_val32 maxcorr=1;
Chris@69: #endif
Chris@69: #if !defined(OVERRIDE_PITCH_XCORR)
Chris@69:    (void)arch;
Chris@69: #endif
Chris@69:    for (i=0;i<max_pitch;i++)
Chris@69:    {
Chris@69:       opus_val32 sum = 0;
Chris@69:       for (j=0;j<len;j++)
Chris@69:          sum = MAC16_16(sum, _x[j], _y[i+j]);
Chris@69:       xcorr[i] = sum;
Chris@69: #ifdef FIXED_POINT
Chris@69:       maxcorr = MAX32(maxcorr, sum);
Chris@69: #endif
Chris@69:    }
Chris@69: #ifdef FIXED_POINT
Chris@69:    return maxcorr;
Chris@69: #endif
Chris@69: 
Chris@69: #else /* Unrolled version of the pitch correlation -- runs faster on x86 and ARM */
Chris@69:    int i;
Chris@69:    /*The EDSP version requires that max_pitch is at least 1, and that _x is
Chris@69:       32-bit aligned.
Chris@69:      Since it's hard to put asserts in assembly, put them here.*/
Chris@69: #ifdef FIXED_POINT
Chris@69:    opus_val32 maxcorr=1;
Chris@69: #endif
Chris@69:    celt_assert(max_pitch>0);
Chris@69:    celt_sig_assert((((unsigned char *)_x-(unsigned char *)NULL)&3)==0);
Chris@69:    for (i=0;i<max_pitch-3;i+=4)
Chris@69:    {
Chris@69:       opus_val32 sum[4]={0,0,0,0};
Chris@69:       xcorr_kernel(_x, _y+i, sum, len, arch);
Chris@69:       xcorr[i]=sum[0];
Chris@69:       xcorr[i+1]=sum[1];
Chris@69:       xcorr[i+2]=sum[2];
Chris@69:       xcorr[i+3]=sum[3];
Chris@69: #ifdef FIXED_POINT
Chris@69:       sum[0] = MAX32(sum[0], sum[1]);
Chris@69:       sum[2] = MAX32(sum[2], sum[3]);
Chris@69:       sum[0] = MAX32(sum[0], sum[2]);
Chris@69:       maxcorr = MAX32(maxcorr, sum[0]);
Chris@69: #endif
Chris@69:    }
Chris@69:    /* In case max_pitch isn't a multiple of 4, do non-unrolled version. */
Chris@69:    for (;i<max_pitch;i++)
Chris@69:    {
Chris@69:       opus_val32 sum;
Chris@69:       sum = celt_inner_prod(_x, _y+i, len, arch);
Chris@69:       xcorr[i] = sum;
Chris@69: #ifdef FIXED_POINT
Chris@69:       maxcorr = MAX32(maxcorr, sum);
Chris@69: #endif
Chris@69:    }
Chris@69: #ifdef FIXED_POINT
Chris@69:    return maxcorr;
Chris@69: #endif
Chris@69: #endif
Chris@69: }
Chris@69: 
Chris@69: void pitch_search(const opus_val16 * OPUS_RESTRICT x_lp, opus_val16 * OPUS_RESTRICT y,
Chris@69:                   int len, int max_pitch, int *pitch, int arch)
Chris@69: {
Chris@69:    int i, j;
Chris@69:    int lag;
Chris@69:    int best_pitch[2]={0,0};
Chris@69:    VARDECL(opus_val16, x_lp4);
Chris@69:    VARDECL(opus_val16, y_lp4);
Chris@69:    VARDECL(opus_val32, xcorr);
Chris@69: #ifdef FIXED_POINT
Chris@69:    opus_val32 maxcorr;
Chris@69:    opus_val32 xmax, ymax;
Chris@69:    int shift=0;
Chris@69: #endif
Chris@69:    int offset;
Chris@69: 
Chris@69:    SAVE_STACK;
Chris@69: 
Chris@69:    celt_assert(len>0);
Chris@69:    celt_assert(max_pitch>0);
Chris@69:    lag = len+max_pitch;
Chris@69: 
Chris@69:    ALLOC(x_lp4, len>>2, opus_val16);
Chris@69:    ALLOC(y_lp4, lag>>2, opus_val16);
Chris@69:    ALLOC(xcorr, max_pitch>>1, opus_val32);
Chris@69: 
Chris@69:    /* Downsample by 2 again */
Chris@69:    for (j=0;j<len>>2;j++)
Chris@69:       x_lp4[j] = x_lp[2*j];
Chris@69:    for (j=0;j<lag>>2;j++)
Chris@69:       y_lp4[j] = y[2*j];
Chris@69: 
Chris@69: #ifdef FIXED_POINT
Chris@69:    xmax = celt_maxabs16(x_lp4, len>>2);
Chris@69:    ymax = celt_maxabs16(y_lp4, lag>>2);
Chris@69:    shift = celt_ilog2(MAX32(1, MAX32(xmax, ymax)))-11;
Chris@69:    if (shift>0)
Chris@69:    {
Chris@69:       for (j=0;j<len>>2;j++)
Chris@69:          x_lp4[j] = SHR16(x_lp4[j], shift);
Chris@69:       for (j=0;j<lag>>2;j++)
Chris@69:          y_lp4[j] = SHR16(y_lp4[j], shift);
Chris@69:       /* Use double the shift for a MAC */
Chris@69:       shift *= 2;
Chris@69:    } else {
Chris@69:       shift = 0;
Chris@69:    }
Chris@69: #endif
Chris@69: 
Chris@69:    /* Coarse search with 4x decimation */
Chris@69: 
Chris@69: #ifdef FIXED_POINT
Chris@69:    maxcorr =
Chris@69: #endif
Chris@69:    celt_pitch_xcorr(x_lp4, y_lp4, xcorr, len>>2, max_pitch>>2, arch);
Chris@69: 
Chris@69:    find_best_pitch(xcorr, y_lp4, len>>2, max_pitch>>2, best_pitch
Chris@69: #ifdef FIXED_POINT
Chris@69:                    , 0, maxcorr
Chris@69: #endif
Chris@69:                    );
Chris@69: 
Chris@69:    /* Finer search with 2x decimation */
Chris@69: #ifdef FIXED_POINT
Chris@69:    maxcorr=1;
Chris@69: #endif
Chris@69:    for (i=0;i<max_pitch>>1;i++)
Chris@69:    {
Chris@69:       opus_val32 sum;
Chris@69:       xcorr[i] = 0;
Chris@69:       if (abs(i-2*best_pitch[0])>2 && abs(i-2*best_pitch[1])>2)
Chris@69:          continue;
Chris@69: #ifdef FIXED_POINT
Chris@69:       sum = 0;
Chris@69:       for (j=0;j<len>>1;j++)
Chris@69:          sum += SHR32(MULT16_16(x_lp[j],y[i+j]), shift);
Chris@69: #else
Chris@69:       sum = celt_inner_prod(x_lp, y+i, len>>1, arch);
Chris@69: #endif
Chris@69:       xcorr[i] = MAX32(-1, sum);
Chris@69: #ifdef FIXED_POINT
Chris@69:       maxcorr = MAX32(maxcorr, sum);
Chris@69: #endif
Chris@69:    }
Chris@69:    find_best_pitch(xcorr, y, len>>1, max_pitch>>1, best_pitch
Chris@69: #ifdef FIXED_POINT
Chris@69:                    , shift+1, maxcorr
Chris@69: #endif
Chris@69:                    );
Chris@69: 
Chris@69:    /* Refine by pseudo-interpolation */
Chris@69:    if (best_pitch[0]>0 && best_pitch[0]<(max_pitch>>1)-1)
Chris@69:    {
Chris@69:       opus_val32 a, b, c;
Chris@69:       a = xcorr[best_pitch[0]-1];
Chris@69:       b = xcorr[best_pitch[0]];
Chris@69:       c = xcorr[best_pitch[0]+1];
Chris@69:       if ((c-a) > MULT16_32_Q15(QCONST16(.7f,15),b-a))
Chris@69:          offset = 1;
Chris@69:       else if ((a-c) > MULT16_32_Q15(QCONST16(.7f,15),b-c))
Chris@69:          offset = -1;
Chris@69:       else
Chris@69:          offset = 0;
Chris@69:    } else {
Chris@69:       offset = 0;
Chris@69:    }
Chris@69:    *pitch = 2*best_pitch[0]-offset;
Chris@69: 
Chris@69:    RESTORE_STACK;
Chris@69: }
Chris@69: 
Chris@69: #ifdef FIXED_POINT
Chris@69: static opus_val16 compute_pitch_gain(opus_val32 xy, opus_val32 xx, opus_val32 yy)
Chris@69: {
Chris@69:    opus_val32 x2y2;
Chris@69:    int sx, sy, shift;
Chris@69:    opus_val32 g;
Chris@69:    opus_val16 den;
Chris@69:    if (xy == 0 || xx == 0 || yy == 0)
Chris@69:       return 0;
Chris@69:    sx = celt_ilog2(xx)-14;
Chris@69:    sy = celt_ilog2(yy)-14;
Chris@69:    shift = sx + sy;
Chris@69:    x2y2 = SHR32(MULT16_16(VSHR32(xx, sx), VSHR32(yy, sy)), 14);
Chris@69:    if (shift & 1) {
Chris@69:       if (x2y2 < 32768)
Chris@69:       {
Chris@69:          x2y2 <<= 1;
Chris@69:          shift--;
Chris@69:       } else {
Chris@69:          x2y2 >>= 1;
Chris@69:          shift++;
Chris@69:       }
Chris@69:    }
Chris@69:    den = celt_rsqrt_norm(x2y2);
Chris@69:    g = MULT16_32_Q15(den, xy);
Chris@69:    g = VSHR32(g, (shift>>1)-1);
Chris@69:    return EXTRACT16(MIN32(g, Q15ONE));
Chris@69: }
Chris@69: #else
Chris@69: static opus_val16 compute_pitch_gain(opus_val32 xy, opus_val32 xx, opus_val32 yy)
Chris@69: {
Chris@69:    return xy/celt_sqrt(1+xx*yy);
Chris@69: }
Chris@69: #endif
Chris@69: 
Chris@69: static const int second_check[16] = {0, 0, 3, 2, 3, 2, 5, 2, 3, 2, 3, 2, 5, 2, 3, 2};
Chris@69: opus_val16 remove_doubling(opus_val16 *x, int maxperiod, int minperiod,
Chris@69:       int N, int *T0_, int prev_period, opus_val16 prev_gain, int arch)
Chris@69: {
Chris@69:    int k, i, T, T0;
Chris@69:    opus_val16 g, g0;
Chris@69:    opus_val16 pg;
Chris@69:    opus_val32 xy,xx,yy,xy2;
Chris@69:    opus_val32 xcorr[3];
Chris@69:    opus_val32 best_xy, best_yy;
Chris@69:    int offset;
Chris@69:    int minperiod0;
Chris@69:    VARDECL(opus_val32, yy_lookup);
Chris@69:    SAVE_STACK;
Chris@69: 
Chris@69:    minperiod0 = minperiod;
Chris@69:    maxperiod /= 2;
Chris@69:    minperiod /= 2;
Chris@69:    *T0_ /= 2;
Chris@69:    prev_period /= 2;
Chris@69:    N /= 2;
Chris@69:    x += maxperiod;
Chris@69:    if (*T0_>=maxperiod)
Chris@69:       *T0_=maxperiod-1;
Chris@69: 
Chris@69:    T = T0 = *T0_;
Chris@69:    ALLOC(yy_lookup, maxperiod+1, opus_val32);
Chris@69:    dual_inner_prod(x, x, x-T0, N, &xx, &xy, arch);
Chris@69:    yy_lookup[0] = xx;
Chris@69:    yy=xx;
Chris@69:    for (i=1;i<=maxperiod;i++)
Chris@69:    {
Chris@69:       yy = yy+MULT16_16(x[-i],x[-i])-MULT16_16(x[N-i],x[N-i]);
Chris@69:       yy_lookup[i] = MAX32(0, yy);
Chris@69:    }
Chris@69:    yy = yy_lookup[T0];
Chris@69:    best_xy = xy;
Chris@69:    best_yy = yy;
Chris@69:    g = g0 = compute_pitch_gain(xy, xx, yy);
Chris@69:    /* Look for any pitch at T/k */
Chris@69:    for (k=2;k<=15;k++)
Chris@69:    {
Chris@69:       int T1, T1b;
Chris@69:       opus_val16 g1;
Chris@69:       opus_val16 cont=0;
Chris@69:       opus_val16 thresh;
Chris@69:       T1 = celt_udiv(2*T0+k, 2*k);
Chris@69:       if (T1 < minperiod)
Chris@69:          break;
Chris@69:       /* Look for another strong correlation at T1b */
Chris@69:       if (k==2)
Chris@69:       {
Chris@69:          if (T1+T0>maxperiod)
Chris@69:             T1b = T0;
Chris@69:          else
Chris@69:             T1b = T0+T1;
Chris@69:       } else
Chris@69:       {
Chris@69:          T1b = celt_udiv(2*second_check[k]*T0+k, 2*k);
Chris@69:       }
Chris@69:       dual_inner_prod(x, &x[-T1], &x[-T1b], N, &xy, &xy2, arch);
Chris@69:       xy = HALF32(xy + xy2);
Chris@69:       yy = HALF32(yy_lookup[T1] + yy_lookup[T1b]);
Chris@69:       g1 = compute_pitch_gain(xy, xx, yy);
Chris@69:       if (abs(T1-prev_period)<=1)
Chris@69:          cont = prev_gain;
Chris@69:       else if (abs(T1-prev_period)<=2 && 5*k*k < T0)
Chris@69:          cont = HALF16(prev_gain);
Chris@69:       else
Chris@69:          cont = 0;
Chris@69:       thresh = MAX16(QCONST16(.3f,15), MULT16_16_Q15(QCONST16(.7f,15),g0)-cont);
Chris@69:       /* Bias against very high pitch (very short period) to avoid false-positives
Chris@69:          due to short-term correlation */
Chris@69:       if (T1<3*minperiod)
Chris@69:          thresh = MAX16(QCONST16(.4f,15), MULT16_16_Q15(QCONST16(.85f,15),g0)-cont);
Chris@69:       else if (T1<2*minperiod)
Chris@69:          thresh = MAX16(QCONST16(.5f,15), MULT16_16_Q15(QCONST16(.9f,15),g0)-cont);
Chris@69:       if (g1 > thresh)
Chris@69:       {
Chris@69:          best_xy = xy;
Chris@69:          best_yy = yy;
Chris@69:          T = T1;
Chris@69:          g = g1;
Chris@69:       }
Chris@69:    }
Chris@69:    best_xy = MAX32(0, best_xy);
Chris@69:    if (best_yy <= best_xy)
Chris@69:       pg = Q15ONE;
Chris@69:    else
Chris@69:       pg = SHR32(frac_div32(best_xy,best_yy+1),16);
Chris@69: 
Chris@69:    for (k=0;k<3;k++)
Chris@69:       xcorr[k] = celt_inner_prod(x, x-(T+k-1), N, arch);
Chris@69:    if ((xcorr[2]-xcorr[0]) > MULT16_32_Q15(QCONST16(.7f,15),xcorr[1]-xcorr[0]))
Chris@69:       offset = 1;
Chris@69:    else if ((xcorr[0]-xcorr[2]) > MULT16_32_Q15(QCONST16(.7f,15),xcorr[1]-xcorr[2]))
Chris@69:       offset = -1;
Chris@69:    else
Chris@69:       offset = 0;
Chris@69:    if (pg > g)
Chris@69:       pg = g;
Chris@69:    *T0_ = 2*T+offset;
Chris@69: 
Chris@69:    if (*T0_<minperiod0)
Chris@69:       *T0_=minperiod0;
Chris@69:    RESTORE_STACK;
Chris@69:    return pg;
Chris@69: }