G.729 postfilter

4 files changed, 683 insertions, 1 deletions

diff --git a/libavcodec/Makefile b/libavcodec/Makefile
index 0c6402320b..211c6b5382 100644
--- a/libavcodec/Makefile
+++ b/libavcodec/Makefile
@@ -159,7 +159,7 @@ OBJS-$(CONFIG_FLIC_DECODER)            += flicvideo.o
 OBJS-$(CONFIG_FOURXM_DECODER)          += 4xm.o
 OBJS-$(CONFIG_FRAPS_DECODER)           += fraps.o
 OBJS-$(CONFIG_FRWU_DECODER)            += frwu.o
-OBJS-$(CONFIG_G729_DECODER)            += g729dec.o lsp.o celp_math.o acelp_filters.o acelp_pitch_delay.o acelp_vectors.o
+OBJS-$(CONFIG_G729_DECODER)            += g729dec.o lsp.o celp_math.o acelp_filters.o acelp_pitch_delay.o acelp_vectors.o g729postfilter.o
 OBJS-$(CONFIG_GIF_DECODER)             += gifdec.o lzw.o
 OBJS-$(CONFIG_GIF_ENCODER)             += gif.o lzwenc.o
 OBJS-$(CONFIG_GSM_DECODER)             += gsmdec.o gsmdec_data.o msgsmdec.o
diff --git a/libavcodec/g729dec.c b/libavcodec/g729dec.c
index b20d3d25c7..bc7fbc13a8 100644
--- a/libavcodec/g729dec.c
+++ b/libavcodec/g729dec.c
@@ -39,6 +39,7 @@
 #include "acelp_pitch_delay.h"
 #include "acelp_vectors.h"
 #include "g729data.h"
+#include "g729postfilter.h"
 
 /**
  * minimum quantized LSF value (3.2.4)
@@ -122,6 +123,16 @@ typedef struct {
     /// previous speech data for LP synthesis filter
     int16_t syn_filter_data[10];
 
+
+    /// residual signal buffer (used in long-term postfilter)
+    int16_t residual[SUBFRAME_SIZE + RES_PREV_DATA_SIZE];
+
+    /// previous speech data for residual calculation filter
+    int16_t res_filter_data[SUBFRAME_SIZE+10];
+
+    /// previous speech data for short-term postfilter
+    int16_t pos_filter_data[SUBFRAME_SIZE+10];
+
     /// (1.14) pitch gain of current and five previous subframes
     int16_t past_gain_pitch[6];
 
@@ -133,6 +144,7 @@ typedef struct {
 
     int16_t onset;              ///< detected onset level (0-2)
     int16_t was_periodic;       ///< whether previous frame was declared as periodic or not (4.4)
+    int16_t ht_prev_data;       ///< previous data for 4.2.3, equation 86
     uint16_t rand_value;        ///< random number generator value (4.4.4)
     int ma_predictor_prev;      ///< switched MA predictor of LSP quantizer from last good frame
 
@@ -625,6 +637,19 @@ static int decode_frame(AVCodecContext *avctx, void *data, int *data_size,
         /* Save data (without postfilter) for use in next subframe. */
         memcpy(ctx->syn_filter_data, synth+SUBFRAME_SIZE, 10 * sizeof(int16_t));
 
+        /* Call postfilter and also update voicing decision for use in next frame. */
+        g729_postfilter(
+                &ctx->dsp,
+                &ctx->ht_prev_data,
+                &is_periodic,
+                &lp[i][0],
+                pitch_delay_int[0],
+                ctx->residual,
+                ctx->res_filter_data,
+                ctx->pos_filter_data,
+                synth+10,
+                SUBFRAME_SIZE);
+
         if (frame_erasure)
             ctx->pitch_delay_int_prev = FFMIN(ctx->pitch_delay_int_prev + 1, PITCH_DELAY_MAX);
         else
diff --git a/libavcodec/g729postfilter.c b/libavcodec/g729postfilter.c
new file mode 100644
index 0000000000..9af6014b9e
--- /dev/null
+++ b/libavcodec/g729postfilter.c
@@ -0,0 +1,562 @@
+/*
+ * G.729, G729 Annex D postfilter
+ * Copyright (c) 2008 Vladimir Voroshilov
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+#include <inttypes.h>
+#include <limits.h>
+
+#include "avcodec.h"
+#include "g729.h"
+#include "acelp_pitch_delay.h"
+#include "g729postfilter.h"
+#include "celp_math.h"
+#include "acelp_filters.h"
+#include "acelp_vectors.h"
+#include "celp_filters.h"
+
+#define FRAC_BITS 15
+#include "mathops.h"
+
+/**
+ * short interpolation filter (of length 33, according to spec)
+ * for computing signal with non-integer delay
+ */
+static const int16_t ff_g729_interp_filt_short[(ANALYZED_FRAC_DELAYS+1)*SHORT_INT_FILT_LEN] = {
+      0, 31650, 28469, 23705, 18050, 12266,  7041,  2873,
+      0, -1597, -2147, -1992, -1492,  -933,  -484,  -188,
+};
+
+/**
+ * long interpolation filter (of length 129, according to spec)
+ * for computing signal with non-integer delay
+ */
+static const int16_t ff_g729_interp_filt_long[(ANALYZED_FRAC_DELAYS+1)*LONG_INT_FILT_LEN] = {
+   0, 31915, 29436, 25569, 20676, 15206,  9639,  4439,
+   0, -3390, -5579, -6549, -6414, -5392, -3773, -1874,
+   0,  1595,  2727,  3303,  3319,  2850,  2030,  1023,
+   0,  -887, -1527, -1860, -1876, -1614, -1150,  -579,
+   0,   501,   859,  1041,  1044,   892,   631,   315,
+   0,  -266,  -453,  -543,  -538,  -455,  -317,  -156,
+   0,   130,   218,   258,   253,   212,   147,    72,
+   0,   -59,  -101,  -122,  -123,  -106,   -77,   -40,
+};
+
+/**
+ * formant_pp_factor_num_pow[i] = FORMANT_PP_FACTOR_NUM^(i+1)
+ */
+static const int16_t formant_pp_factor_num_pow[10]= {
+  /* (0.15) */
+  18022, 9912, 5451, 2998, 1649, 907, 499, 274, 151, 83
+};
+
+/**
+ * formant_pp_factor_den_pow[i] = FORMANT_PP_FACTOR_DEN^(i+1)
+ */
+static const int16_t formant_pp_factor_den_pow[10] = {
+  /* (0.15) */
+  22938, 16057, 11240, 7868, 5508, 3856, 2699, 1889, 1322, 925
+};
+
+/**
+ * \brief Residual signal calculation (4.2.1 if G.729)
+ * \param out [out] output data filtered through A(z/FORMANT_PP_FACTOR_NUM)
+ * \param filter_coeffs (3.12) A(z/FORMANT_PP_FACTOR_NUM) filter coefficients
+ * \param in input speech data to process
+ * \param subframe_size size of one subframe
+ *
+ * \note in buffer must contain 10 items of previous speech data before top of the buffer
+ * \remark It is safe to pass the same buffer for input and output.
+ */
+static void residual_filter(int16_t* out, const int16_t* filter_coeffs, const int16_t* in,
+                            int subframe_size)
+{
+    int i, n;
+
+    for (n = subframe_size - 1; n >= 0; n--) {
+        int sum = 0x800;
+        for (i = 0; i < 10; i++)
+            sum += filter_coeffs[i] * in[n - i - 1];
+
+        out[n] = in[n] + (sum >> 12);
+    }
+}
+
+/**
+ * \brief long-term postfilter (4.2.1)
+ * \param dsp initialized DSP context
+ * \param pitch_delay_int integer part of the pitch delay in the first subframe
+ * \param residual filtering input data
+ * \param residual_filt [out] speech signal with applied A(z/FORMANT_PP_FACTOR_NUM) filter
+ * \param subframe_size size of subframe
+ *
+ * \return 0 if long-term prediction gain is less than 3dB, 1 -  otherwise
+ */
+static int16_t long_term_filter(DSPContext *dsp, int pitch_delay_int,
+                                const int16_t* residual, int16_t *residual_filt,
+                                int subframe_size)
+{
+    int i, k, n, tmp, tmp2;
+    int sum;
+    int L_temp0;
+    int L_temp1;
+    int64_t L64_temp0;
+    int64_t L64_temp1;
+    int16_t shift;
+    int corr_int_num, corr_int_den;
+
+    int ener;
+    int16_t sh_ener;
+
+    int16_t gain_num,gain_den; //selected signal's gain numerator and denominator
+    int16_t sh_gain_num, sh_gain_den;
+    int gain_num_square;
+
+    int16_t gain_long_num,gain_long_den; //filtered through long interpolation filter signal's gain numerator and denominator
+    int16_t sh_gain_long_num, sh_gain_long_den;
+
+    int16_t best_delay_int, best_delay_frac;
+
+    int16_t delayed_signal_offset;
+    int lt_filt_factor_a, lt_filt_factor_b;
+
+    int16_t * selected_signal;
+    const int16_t * selected_signal_const; //Necessary to avoid compiler warning
+
+    int16_t sig_scaled[SUBFRAME_SIZE + RES_PREV_DATA_SIZE];
+    int16_t delayed_signal[ANALYZED_FRAC_DELAYS][SUBFRAME_SIZE+1];
+    int corr_den[ANALYZED_FRAC_DELAYS][2];
+
+    tmp = 0;
+    for(i=0; i<subframe_size + RES_PREV_DATA_SIZE; i++)
+        tmp |= FFABS(residual[i]);
+
+    if(!tmp)
+        shift = 3;
+    else
+        shift = av_log2(tmp) - 11;
+
+    if (shift > 0)
+        for (i = 0; i < subframe_size + RES_PREV_DATA_SIZE; i++)
+            sig_scaled[i] = residual[i] >> shift;
+    else
+        for (i = 0; i < subframe_size + RES_PREV_DATA_SIZE; i++)
+            sig_scaled[i] = residual[i] << -shift;
+
+    /* Start of best delay searching code */
+    gain_num = 0;
+
+    ener = dsp->scalarproduct_int16(sig_scaled + RES_PREV_DATA_SIZE,
+                                    sig_scaled + RES_PREV_DATA_SIZE,
+                                    subframe_size, 0);
+    if (ener) {
+        sh_ener = FFMAX(av_log2(ener) - 14, 0);
+        ener >>= sh_ener;
+        /* Search for best pitch delay.
+
+                       sum{ r(n) * r(k,n) ] }^2
+           R'(k)^2 := -------------------------
+                       sum{ r(k,n) * r(k,n) }
+
+
+           R(T)    :=  sum{ r(n) * r(n-T) ] }
+
+
+           where
+           r(n-T) is integer delayed signal with delay T
+           r(k,n) is non-integer delayed signal with integer delay best_delay
+           and fractional delay k */
+
+        /* Find integer delay best_delay which maximizes correlation R(T).
+
+           This is also equals to numerator of R'(0),
+           since the fine search (second step) is done with 1/8
+           precision around best_delay. */
+        corr_int_num = 0;
+        best_delay_int = pitch_delay_int - 1;
+        for (i = pitch_delay_int - 1; i <= pitch_delay_int + 1; i++) {
+            sum = dsp->scalarproduct_int16(sig_scaled + RES_PREV_DATA_SIZE,
+                                           sig_scaled + RES_PREV_DATA_SIZE - i,
+                                           subframe_size, 0);
+            if (sum > corr_int_num) {
+                corr_int_num = sum;
+                best_delay_int = i;
+            }
+        }
+        if (corr_int_num) {
+            /* Compute denominator of pseudo-normalized correlation R'(0). */
+            corr_int_den = dsp->scalarproduct_int16(sig_scaled - best_delay_int + RES_PREV_DATA_SIZE,
+                                                    sig_scaled - best_delay_int + RES_PREV_DATA_SIZE,
+                                                    subframe_size, 0);
+
+            /* Compute signals with non-integer delay k (with 1/8 precision),
+               where k is in [0;6] range.
+               Entire delay is qual to best_delay+(k+1)/8
+               This is archieved by applying an interpolation filter of
+               legth 33 to source signal. */
+            for (k = 0; k < ANALYZED_FRAC_DELAYS; k++) {
+                ff_acelp_interpolate(&delayed_signal[k][0],
+                                     &sig_scaled[RES_PREV_DATA_SIZE - best_delay_int],
+                                     ff_g729_interp_filt_short,
+                                     ANALYZED_FRAC_DELAYS+1,
+                                     8 - k - 1,
+                                     SHORT_INT_FILT_LEN,
+                                     subframe_size + 1);
+            }
+
+            /* Compute denominator of pseudo-normalized correlation R'(k).
+
+                 corr_den[k][0] is square root of R'(k) denominator, for int(T) == int(T0)
+                 corr_den[k][1] is square root of R'(k) denominator, for int(T) == int(T0)+1
+
+              Also compute maximum value of above denominators over all k. */
+            tmp = corr_int_den;
+            for (k = 0; k < ANALYZED_FRAC_DELAYS; k++) {
+                sum = dsp->scalarproduct_int16(&delayed_signal[k][1],
+                                               &delayed_signal[k][1],
+                                               subframe_size - 1, 0);
+                corr_den[k][0] = sum + delayed_signal[k][0            ] * delayed_signal[k][0            ];
+                corr_den[k][1] = sum + delayed_signal[k][subframe_size] * delayed_signal[k][subframe_size];
+
+                tmp = FFMAX3(tmp, corr_den[k][0], corr_den[k][1]);
+            }
+
+            sh_gain_den = av_log2(tmp) - 14;
+            if (sh_gain_den >= 0) {
+
+                sh_gain_num =  FFMAX(sh_gain_den, sh_ener);
+                /* Loop through all k and find delay that maximizes
+                   R'(k) correlation.
+                   Search is done in [int(T0)-1; intT(0)+1] range
+                   with 1/8 precision. */
+                delayed_signal_offset = 1;
+                best_delay_frac = 0;
+                gain_den = corr_int_den >> sh_gain_den;
+                gain_num = corr_int_num >> sh_gain_num;
+                gain_num_square = gain_num * gain_num;
+                for (k = 0; k < ANALYZED_FRAC_DELAYS; k++) {
+                    for (i = 0; i < 2; i++) {
+                        int16_t gain_num_short, gain_den_short;
+                        int gain_num_short_square;
+                        /* Compute numerator of pseudo-normalized
+                           correlation R'(k). */
+                        sum = dsp->scalarproduct_int16(&delayed_signal[k][i],
+                                                       sig_scaled + RES_PREV_DATA_SIZE,
+                                                       subframe_size, 0);
+                        gain_num_short = FFMAX(sum >> sh_gain_num, 0);
+
+                        /*
+                                      gain_num_short_square                gain_num_square
+                           R'(T)^2 = -----------------------, max R'(T)^2= --------------
+                                           den                                 gain_den
+                        */
+                        gain_num_short_square = gain_num_short * gain_num_short;
+                        gain_den_short = corr_den[k][i] >> sh_gain_den;
+
+                        tmp = MULL(gain_num_short_square, gain_den, FRAC_BITS);
+                        tmp2 = MULL(gain_num_square, gain_den_short, FRAC_BITS);
+
+                        // R'(T)^2 > max R'(T)^2
+                        if (tmp > tmp2) {
+                            gain_num = gain_num_short;
+                            gain_den = gain_den_short;
+                            gain_num_square = gain_num_short_square;
+                            delayed_signal_offset = i;
+                            best_delay_frac = k + 1;
+                        }
+                    }
+                }
+
+                /*
+                       R'(T)^2
+                  2 * --------- < 1
+                        R(0)
+                */
+                L64_temp0 =  (int64_t)gain_num_square  << ((sh_gain_num << 1) + 1);
+                L64_temp1 = ((int64_t)gain_den * ener) << (sh_gain_den + sh_ener);
+                if (L64_temp0 < L64_temp1)
+                    gain_num = 0;
+            } // if(sh_gain_den >= 0)
+        } // if(corr_int_num)
+    } // if(ener)
+    /* End of best delay searching code  */
+
+    if (!gain_num) {
+        memcpy(residual_filt, residual + RES_PREV_DATA_SIZE, subframe_size * sizeof(int16_t));
+
+        /* Long-term prediction gain is less than 3dB. Long-term postfilter is disabled. */
+        return 0;
+    }
+    if (best_delay_frac) {
+        /* Recompute delayed signal with an interpolation filter of length 129. */
+        ff_acelp_interpolate(residual_filt,
+                             &sig_scaled[RES_PREV_DATA_SIZE - best_delay_int + delayed_signal_offset],
+                             ff_g729_interp_filt_long,
+                             ANALYZED_FRAC_DELAYS + 1,
+                             8 - best_delay_frac,
+                             LONG_INT_FILT_LEN,
+                             subframe_size + 1);
+        /* Compute R'(k) correlation's numerator. */
+        sum = dsp->scalarproduct_int16(residual_filt,
+                                       sig_scaled + RES_PREV_DATA_SIZE,
+                                       subframe_size, 0);
+
+        if (sum < 0) {
+            gain_long_num = 0;
+            sh_gain_long_num = 0;
+        } else {
+            tmp = FFMAX(av_log2(sum) - 14, 0);
+            sum >>= tmp;
+            gain_long_num = sum;
+            sh_gain_long_num = tmp;
+        }
+
+        /* Compute R'(k) correlation's denominator. */
+        sum = dsp->scalarproduct_int16(residual_filt, residual_filt, subframe_size, 0);
+
+        tmp = FFMAX(av_log2(sum) - 14, 0);
+        sum >>= tmp;
+        gain_long_den = sum;
+        sh_gain_long_den = tmp;
+
+        /* Select between original and delayed signal.
+           Delayed signal will be selected if it increases R'(k)
+           correlation. */
+        L_temp0 = gain_num * gain_num;
+        L_temp0 = MULL(L_temp0, gain_long_den, FRAC_BITS);
+
+        L_temp1 = gain_long_num * gain_long_num;
+        L_temp1 = MULL(L_temp1, gain_den, FRAC_BITS);
+
+        tmp = ((sh_gain_long_num - sh_gain_num) << 1) - (sh_gain_long_den - sh_gain_den);
+        if (tmp > 0)
+            L_temp0 >>= tmp;
+        else
+            L_temp1 >>= -tmp;
+
+        /* Check if longer filter increases the values of R'(k). */
+        if (L_temp1 > L_temp0) {
+            /* Select long filter. */
+            selected_signal = residual_filt;
+            gain_num = gain_long_num;
+            gain_den = gain_long_den;
+            sh_gain_num = sh_gain_long_num;
+            sh_gain_den = sh_gain_long_den;
+        } else
+            /* Select short filter. */
+            selected_signal = &delayed_signal[best_delay_frac-1][delayed_signal_offset];
+
+        /* Rescale selected signal to original value. */
+        if (shift > 0)
+            for (i = 0; i < subframe_size; i++)
+                selected_signal[i] <<= shift;
+        else
+            for (i = 0; i < subframe_size; i++)
+                selected_signal[i] >>= -shift;
+
+        /* necessary to avoid compiler warning */
+        selected_signal_const = selected_signal;
+    } // if(best_delay_frac)
+    else
+        selected_signal_const = residual + RES_PREV_DATA_SIZE - (best_delay_int + 1 - delayed_signal_offset);
+#ifdef G729_BITEXACT
+    tmp = sh_gain_num - sh_gain_den;
+    if (tmp > 0)
+        gain_den >>= tmp;
+    else
+        gain_num >>= -tmp;
+
+    if (gain_num > gain_den)
+        lt_filt_factor_a = MIN_LT_FILT_FACTOR_A;
+    else {
+        gain_num >>= 2;
+        gain_den >>= 1;
+        lt_filt_factor_a = (gain_den << 15) / (gain_den + gain_num);
+    }
+#else
+    L64_temp0 = ((int64_t)gain_num) << (sh_gain_num - 1);
+    L64_temp1 = ((int64_t)gain_den) << sh_gain_den;
+    lt_filt_factor_a = FFMAX((L64_temp1 << 15) / (L64_temp1 + L64_temp0), MIN_LT_FILT_FACTOR_A);
+#endif
+
+    /* Filter through selected filter. */
+    lt_filt_factor_b = 32767 - lt_filt_factor_a + 1;
+
+    ff_acelp_weighted_vector_sum(residual_filt, residual + RES_PREV_DATA_SIZE,
+                                 selected_signal_const,
+                                 lt_filt_factor_a, lt_filt_factor_b,
+                                 1<<14, 15, subframe_size);
+
+    // Long-term prediction gain is larger than 3dB.
+    return 1;
+}
+
+/**
+ * \brief Calculate reflection coefficient for tilt compensation filter (4.2.3).
+ * \param dsp initialized DSP context
+ * \param lp_gn (3.12) coefficients of A(z/FORMANT_PP_FACTOR_NUM) filter
+ * \param lp_gd (3.12) coefficients of A(z/FORMANT_PP_FACTOR_DEN) filter
+ * \param speech speech to update
+ * \param subframe_size size of subframe
+ *
+ * \return (3.12) reflection coefficient
+ *
+ * \remark The routine also calculates the gain term for the short-term
+ *         filter (gf) and multiplies the speech data by 1/gf.
+ *
+ * \note All members of lp_gn, except 10-19 must be equal to zero.
+ */
+static int16_t get_tilt_comp(DSPContext *dsp, int16_t *lp_gn,
+                             const int16_t *lp_gd, int16_t* speech,
+                             int subframe_size)
+{
+    int rh1,rh0; // (3.12)
+    int temp;
+    int i;
+    int gain_term;
+
+    lp_gn[10] = 4096; //1.0 in (3.12)
+
+    /* Apply 1/A(z/FORMANT_PP_FACTOR_DEN) filter to hf. */
+    ff_celp_lp_synthesis_filter(lp_gn + 11, lp_gd + 1, lp_gn + 11, 22, 10, 0, 0x800);
+    /* Now lp_gn (starting with 10) contains impulse response
+       of A(z/FORMANT_PP_FACTOR_NUM)/A(z/FORMANT_PP_FACTOR_DEN) filter. */
+
+    rh0 = dsp->scalarproduct_int16(lp_gn + 10, lp_gn + 10, 20, 0);
+    rh1 = dsp->scalarproduct_int16(lp_gn + 10, lp_gn + 11, 20, 0);
+
+    /* downscale to avoid overflow */
+    temp = av_log2(rh0) - 14;
+    if (temp > 0) {
+        rh0 >>= temp;
+        rh1 >>= temp;
+    }
+
+    if (FFABS(rh1) > rh0 || !rh0)
+        return 0;
+
+    gain_term = 0;
+    for (i = 0; i < 20; i++)
+        gain_term += FFABS(lp_gn[i + 10]);
+    gain_term >>= 2; // (3.12) -> (5.10)
+
+    if (gain_term > 0x400) { // 1.0 in (5.10)
+        temp = 0x2000000 / gain_term; // 1.0/gain_term in (0.15)
+        for (i = 0; i < subframe_size; i++)
+            speech[i] = (speech[i] * temp + 0x4000) >> 15;
+    }
+
+    return -(rh1 << 15) / rh0;
+}
+
+/**
+ * \brief Apply tilt compensation filter (4.2.3).
+ * \param res_pst [in/out] residual signal (partially filtered)
+ * \param k1 (3.12) reflection coefficient
+ * \param subframe_size size of subframe
+ * \param ht_prev_data previous data for 4.2.3, equation 86
+ *
+ * \return new value for ht_prev_data
+*/
+static int16_t apply_tilt_comp(int16_t* out, int16_t* res_pst, int refl_coeff,
+                               int subframe_size, int16_t ht_prev_data)
+{
+    int tmp, tmp2;
+    int i;
+    int gt, ga;
+    int fact, sh_fact;
+
+    if (refl_coeff > 0) {
+        gt = (refl_coeff * G729_TILT_FACTOR_PLUS + 0x4000) >> 15;
+        fact = 0x4000; // 0.5 in (0.15)
+        sh_fact = 15;
+    } else {
+        gt = (refl_coeff * G729_TILT_FACTOR_MINUS + 0x4000) >> 15;
+        fact = 0x800; // 0.5 in (3.12)
+        sh_fact = 12;
+    }
+    ga = (fact << 15) / av_clip_int16(32768 - FFABS(gt));
+    gt >>= 1;
+
+    /* Apply tilt compensation filter to signal. */
+    tmp = res_pst[subframe_size - 1];
+
+    for (i = subframe_size - 1; i >= 1; i--) {
+        tmp2 = (res_pst[i] << 15) + ((gt * res_pst[i-1]) << 1);
+        tmp2 = (tmp2 + 0x4000) >> 15;
+
+        tmp2 = (tmp2 * ga * 2 + fact) >> sh_fact;
+        out[i] = tmp2;
+    }
+    tmp2 = (res_pst[0] << 15) + ((gt * ht_prev_data) << 1);
+    tmp2 = (tmp2 + 0x4000) >> 15;
+    tmp2 = (tmp2 * ga * 2 + fact) >> sh_fact;
+    out[0] = tmp2;
+
+    return tmp;
+}
+
+void g729_postfilter(DSPContext *dsp, int16_t* ht_prev_data, int16_t* voicing,
+                     const int16_t *lp_filter_coeffs, int pitch_delay_int,
+                     int16_t* residual, int16_t* res_filter_data,
+                     int16_t* pos_filter_data, int16_t *speech, int subframe_size)
+{
+    int16_t residual_filt_buf[SUBFRAME_SIZE+10];
+    int16_t lp_gn[33]; // (3.12)
+    int16_t lp_gd[11]; // (3.12)
+    int tilt_comp_coeff;
+    int i;
+
+    /* Zero-filling is necessary for tilt-compensation filter. */
+    memset(lp_gn, 0, 33 * sizeof(int16_t));
+
+    /* Calculate A(z/FORMANT_PP_FACTOR_NUM) filter coefficients. */
+    for (i = 0; i < 10; i++)
+        lp_gn[i + 11] = (lp_filter_coeffs[i + 1] * formant_pp_factor_num_pow[i] + 0x4000) >> 15;
+
+    /* Calculate A(z/FORMANT_PP_FACTOR_DEN) filter coefficients. */
+    for (i = 0; i < 10; i++)
+        lp_gd[i + 1] = (lp_filter_coeffs[i + 1] * formant_pp_factor_den_pow[i] + 0x4000) >> 15;
+
+    /* residual signal calculation (one-half of short-term postfilter) */
+    memcpy(speech - 10, res_filter_data, 10 * sizeof(int16_t));
+    residual_filter(residual + RES_PREV_DATA_SIZE, lp_gn + 11, speech, subframe_size);
+    /* Save data to use it in the next subframe. */
+    memcpy(res_filter_data, speech + subframe_size - 10, 10 * sizeof(int16_t));
+
+    /* long-term filter. If long-term prediction gain is larger than 3dB (returned value is
+       nonzero) then declare current subframe as periodic. */
+    *voicing = FFMAX(*voicing, long_term_filter(dsp, pitch_delay_int,
+                                                residual, residual_filt_buf + 10,
+                                                subframe_size));
+
+    /* shift residual for using in next subframe */
+    memmove(residual, residual + subframe_size, RES_PREV_DATA_SIZE * sizeof(int16_t));
+
+    /* short-term filter tilt compensation */
+    tilt_comp_coeff = get_tilt_comp(dsp, lp_gn, lp_gd, residual_filt_buf + 10, subframe_size);
+
+    /* Apply second half of short-term postfilter: 1/A(z/FORMANT_PP_FACTOR_DEN) */
+    ff_celp_lp_synthesis_filter(pos_filter_data + 10, lp_gd + 1,
+                                residual_filt_buf + 10,
+                                subframe_size, 10, 0, 0x800);
+    memcpy(pos_filter_data, pos_filter_data + subframe_size, 10 * sizeof(int16_t));
+
+    *ht_prev_data = apply_tilt_comp(speech, pos_filter_data + 10, tilt_comp_coeff,
+                                    subframe_size, *ht_prev_data);
+}
diff --git a/libavcodec/g729postfilter.h b/libavcodec/g729postfilter.h
new file mode 100644
index 0000000000..07667994d5
--- /dev/null
+++ b/libavcodec/g729postfilter.h
@@ -0,0 +1,95 @@
+/*
+ * G.729, G729 Annex D postfilter
+ * Copyright (c) 2008 Vladimir Voroshilov
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+#ifndef FFMPEG_G729POSTFILTER_H
+#define FFMPEG_G729POSTFILTER_H
+
+#include <stdint.h>
+
+/**
+ * tilt compensation factor (G.729, k1>0)
+ * 0.2 in Q15
+ */
+#define G729_TILT_FACTOR_PLUS       6554
+
+/**
+ * tilt compensation factor (G.729, k1<0)
+ * 0.9 in Q15
+ */
+#define G729_TILT_FACTOR_MINUS     29491
+
+/* 4.2.2 */
+#define FORMANT_PP_FACTOR_NUM  18022             //0.55 in Q15
+#define FORMANT_PP_FACTOR_DEN  22938             //0.70 in Q15
+
+/**
+ * 1.0 / (1.0 + 0.5) in Q15
+ * where 0.5 is the minimum value of
+ * weight factor, controlling amount of long-term postfiltering
+ */
+#define MIN_LT_FILT_FACTOR_A       21845
+
+/**
+ * Short interpolation filter length
+ */
+#define SHORT_INT_FILT_LEN         2
+
+/**
+ * Long interpolation filter length
+ */
+#define LONG_INT_FILT_LEN          8
+
+/**
+ * Number of analyzed fractional pitch delays in second stage of long-term
+ * postfilter
+ */
+#define ANALYZED_FRAC_DELAYS       7
+
+/**
+ * Amount of past residual signal data stored in buffer
+ */
+#define RES_PREV_DATA_SIZE (PITCH_DELAY_MAX + LONG_INT_FILT_LEN + 1)
+
+/**
+ * \brief Signal postfiltering (4.2)
+ * \param dsp initialized DSP context
+ * \param ht_prev_data [in/out] (Q12) pointer to variable receiving tilt
+ *                     compensation filter data from previous subframe
+ * \param voicing [in/out] (Q0) pointer to variable receiving voicing decision
+ * \param lp_filter_coeffs (Q12) LP filter coefficients
+ * \param pitch_delay_int integer part of the pitch delay
+ * \param residual [in/out] (Q0) residual signal buffer (used in long-term postfilter)
+ * \param res_filter_data [in/out] (Q0) speech data of previous subframe
+ * \param pos_filter_data [in/out] (Q0) previous speech data for short-term postfilter
+ * \param speech [in/out] (Q0) signal buffer
+ * \param subframe_size size of subframe
+ *
+ * Filtering has the following  stages:
+ *   Long-term postfilter (4.2.1)
+ *   Short-term postfilter (4.2.2).
+ *   Tilt-compensation (4.2.3)
+ */
+void g729_postfilter(DSPContext *dsp, int16_t* ht_prev_data, int16_t* voicing,
+                     const int16_t *lp_filter_coeffs, int pitch_delay_int,
+                     int16_t* residual, int16_t* res_filter_data,
+                     int16_t* pos_filter_data, int16_t *speech,
+                     int subframe_size);
+
+#endif // FFMPEG_G729POSTFILTER_H