libavcodec/celp_filters.c

   1 /*
   2  * various filters for ACELP-based codecs
   3  *
   4  * Copyright (c) 2008 Vladimir Voroshilov
   5  *
   6  * This file is part of FFmpeg.
   7  *
   8  * FFmpeg 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  * FFmpeg 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 FFmpeg; 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 "avcodec.h"
  26 #include "celp_filters.h"
  27
  28 void ff_celp_convolve_circ(int16_t* fc_out,
  29                            const int16_t* fc_in,
  30                            const int16_t* filter,
  31                            int len)
  32 {
  33     int i, k;
  34
  35     memset(fc_out, 0, len * sizeof(int16_t));
  36
  37     /* Since there are few pulses over an entire subframe (i.e. almost
  38        all fc_in[i] are zero) it is faster to loop over fc_in first. */
  39     for (i = 0; i < len; i++) {
  40         if (fc_in[i]) {
  41             for (k = 0; k < i; k++)
  42                 fc_out[k] += (fc_in[i] * filter[len + k - i]) >> 15;
  43
  44             for (k = i; k < len; k++)
  45                 fc_out[k] += (fc_in[i] * filter[      k - i]) >> 15;
  46         }
  47     }
  48 }
  49
  50 void ff_celp_circ_addf(float *out, const float *in,
  51                        const float *lagged, int lag, float fac, int n)
  52 {
  53     int k;
  54     for (k = 0; k < lag; k++)
  55         out[k] = in[k] + fac * lagged[n + k - lag];
  56     for (; k < n; k++)
  57         out[k] = in[k] + fac * lagged[    k - lag];
  58 }
  59
  60 int ff_celp_lp_synthesis_filter(int16_t *out,
  61                                 const int16_t* filter_coeffs,
  62                                 const int16_t* in,
  63                                 int buffer_length,
  64                                 int filter_length,
  65                                 int stop_on_overflow,
  66                                 int rounder)
  67 {
  68     int i,n;
  69
  70     for (n = 0; n < buffer_length; n++) {
  71         int sum = rounder;
  72         for (i = 1; i <= filter_length; i++)
  73             sum -= filter_coeffs[i-1] * out[n-i];
  74
  75         sum = (sum >> 12) + in[n];
  76
  77         if (sum + 0x8000 > 0xFFFFU) {
  78             if (stop_on_overflow)
  79                 return 1;
  80             sum = (sum >> 31) ^ 32767;
  81         }
  82         out[n] = sum;
  83     }
  84
  85     return 0;
  86 }
  87
  88 void ff_celp_lp_synthesis_filterf(float *out,
  89                                   const float* filter_coeffs,
  90                                   const float* in,
  91                                   int buffer_length,
  92                                   int filter_length)
  93 {
  94     int i,n;
  95
  96     for (n = 0; n < buffer_length; n++) {
  97         out[n] = in[n];
  98         for (i = 1; i <= filter_length; i++)
  99             out[n] -= filter_coeffs[i-1] * out[n-i];
 100     }
 101 }
 102
 103 void ff_celp_lp_zero_synthesis_filterf(float *out,
 104                                        const float* filter_coeffs,
 105                                        const float* in,
 106                                        int buffer_length,
 107                                        int filter_length)
 108 {
 109     int i,n;
 110
 111     for (n = 0; n < buffer_length; n++) {
 112         out[n] = in[n];
 113         for (i = 1; i <= filter_length; i++)
 114             out[n] += filter_coeffs[i-1] * in[n-i];
 115     }
 116 }