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 int ff_celp_lp_synthesis_filter(int16_t *out,
  51                                 const int16_t* filter_coeffs,
  52                                 const int16_t* in,
  53                                 int buffer_length,
  54                                 int filter_length,
  55                                 int stop_on_overflow,
  56                                 int rounder)
  57 {
  58     int i,n;
  59
  60     // Avoids a +1 in the inner loop.
  61     filter_length++;
  62
  63     for (n = 0; n < buffer_length; n++) {
  64         int sum = rounder;
  65         for (i = 1; i < filter_length; i++)
  66             sum -= filter_coeffs[i-1] * out[n-i];
  67
  68         sum = (sum >> 12) + in[n];
  69
  70         if (sum + 0x8000 > 0xFFFFU) {
  71             if (stop_on_overflow)
  72                 return 1;
  73             sum = (sum >> 31) ^ 32767;
  74         }
  75         out[n] = sum;
  76     }
  77
  78     return 0;
  79 }
  80
  81 void ff_celp_lp_synthesis_filterf(float *out,
  82                                   const float* filter_coeffs,
  83                                   const float* in,
  84                                   int buffer_length,
  85                                   int filter_length)
  86 {
  87     int i,n;
  88
  89     // Avoids a +1 in the inner loop.
  90     filter_length++;
  91
  92     for (n = 0; n < buffer_length; n++) {
  93         out[n] = in[n];
  94         for (i = 1; i < filter_length; i++)
  95             out[n] -= filter_coeffs[i-1] * out[n-i];
  96     }
  97 }
  98
  99 void ff_celp_lp_zero_synthesis_filterf(float *out,
 100                                        const float* filter_coeffs,
 101                                        const float* in,
 102                                        int buffer_length,
 103                                        int filter_length)
 104 {
 105     int i,n;
 106
 107     // Avoids a +1 in the inner loop.
 108     filter_length++;
 109
 110     for (n = 0; n < buffer_length; n++) {
 111         out[n] = in[n];
 112         for (i = 1; i < filter_length; i++)
 113             out[n] -= filter_coeffs[i-1] * in[n-i];
 114     }
 115 }