libavcodec/acelp_filters.c

   1 /*
   2  * various filters for ACELP-based codecs
   3  *
   4  * Copyright (c) 2008 Vladimir Voroshilov
   5  *
   6  * This file is part of Libav.
   7  *
   8  * Libav is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU Lesser General Public
  10  * License as published by the Free Software Foundation; either
  11  * version 2.1 of the License, or (at your option) any later version.
  12  *
  13  * Libav is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  16  * Lesser General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU Lesser General Public
  19  * License along with Libav; if not, write to the Free Software
  20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  21  */
  22
  23 #include <inttypes.h>
  24
  25 #include "libavutil/common.h"
  26 #include "avcodec.h"
  27 #include "acelp_filters.h"
  28
  29 const int16_t ff_acelp_interp_filter[61] = { /* (0.15) */
  30   29443, 28346, 25207, 20449, 14701,  8693,
  31    3143, -1352, -4402, -5865, -5850, -4673,
  32   -2783,  -672,  1211,  2536,  3130,  2991,
  33    2259,  1170,     0, -1001, -1652, -1868,
  34   -1666, -1147,  -464,   218,   756,  1060,
  35    1099,   904,   550,   135,  -245,  -514,
  36    -634,  -602,  -451,  -231,     0,   191,
  37     308,   340,   296,   198,    78,   -36,
  38    -120,  -163,  -165,  -132,   -79,   -19,
  39      34,    73,    91,    89,    70,    38,
  40       0,
  41 };
  42
  43 void ff_acelp_interpolate(int16_t* out, const int16_t* in,
  44                           const int16_t* filter_coeffs, int precision,
  45                           int frac_pos, int filter_length, int length)
  46 {
  47     int n, i;
  48
  49     assert(frac_pos >= 0 && frac_pos < precision);
  50
  51     for (n = 0; n < length; n++) {
  52         int idx = 0;
  53         int v = 0x4000;
  54
  55         for (i = 0; i < filter_length;) {
  56
  57             /* The reference G.729 and AMR fixed point code performs clipping after
  58                each of the two following accumulations.
  59                Since clipping affects only the synthetic OVERFLOW test without
  60                causing an int type overflow, it was moved outside the loop. */
  61
  62             /*  R(x):=ac_v[-k+x]
  63                 v += R(n-i)*ff_acelp_interp_filter(t+6i)
  64                 v += R(n+i+1)*ff_acelp_interp_filter(6-t+6i) */
  65
  66             v += in[n + i] * filter_coeffs[idx + frac_pos];
  67             idx += precision;
  68             i++;
  69             v += in[n - i] * filter_coeffs[idx - frac_pos];
  70         }
  71         if (av_clip_int16(v >> 15) != (v >> 15))
  72             av_log(NULL, AV_LOG_WARNING, "overflow that would need cliping in ff_acelp_interpolate()\n");
  73         out[n] = v >> 15;
  74     }
  75 }
  76
  77 void ff_acelp_interpolatef(float *out, const float *in,
  78                            const float *filter_coeffs, int precision,
  79                            int frac_pos, int filter_length, int length)
  80 {
  81     int n, i;
  82
  83     for (n = 0; n < length; n++) {
  84         int idx = 0;
  85         float v = 0;
  86
  87         for (i = 0; i < filter_length;) {
  88             v += in[n + i] * filter_coeffs[idx + frac_pos];
  89             idx += precision;
  90             i++;
  91             v += in[n - i] * filter_coeffs[idx - frac_pos];
  92         }
  93         out[n] = v;
  94     }
  95 }
  96
  97
  98 void ff_acelp_high_pass_filter(int16_t* out, int hpf_f[2],
  99                                const int16_t* in, int length)
 100 {
 101     int i;
 102     int tmp;
 103
 104     for (i = 0; i < length; i++) {
 105         tmp  = (hpf_f[0]* 15836LL) >> 13;
 106         tmp += (hpf_f[1]* -7667LL) >> 13;
 107         tmp += 7699 * (in[i] - 2*in[i-1] + in[i-2]);
 108
 109         /* With "+0x800" rounding, clipping is needed
 110            for ALGTHM and SPEECH tests. */
 111         out[i] = av_clip_int16((tmp + 0x800) >> 12);
 112
 113         hpf_f[1] = hpf_f[0];
 114         hpf_f[0] = tmp;
 115     }
 116 }
 117
 118 void ff_acelp_apply_order_2_transfer_function(float *out, const float *in,
 119                                               const float zero_coeffs[2],
 120                                               const float pole_coeffs[2],
 121                                               float gain, float mem[2], int n)
 122 {
 123     int i;
 124     float tmp;
 125
 126     for (i = 0; i < n; i++) {
 127         tmp = gain * in[i] - pole_coeffs[0] * mem[0] - pole_coeffs[1] * mem[1];
 128         out[i] =       tmp + zero_coeffs[0] * mem[0] + zero_coeffs[1] * mem[1];
 129
 130         mem[1] = mem[0];
 131         mem[0] = tmp;
 132     }
 133 }
 134
 135 void ff_tilt_compensation(float *mem, float tilt, float *samples, int size)
 136 {
 137     float new_tilt_mem = samples[size - 1];
 138     int i;
 139
 140     for (i = size - 1; i > 0; i--)
 141         samples[i] -= tilt * samples[i - 1];
 142
 143     samples[0] -= tilt * *mem;
 144     *mem = new_tilt_mem;
 145 }