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(
  29         int16_t* fc_out,
  30         const int16_t* fc_in,
  31         const int16_t* filter,
  32         int len)
  33 {
  34     int i, k;
  35
  36     memset(fc_out, 0, len * sizeof(int16_t));
  37
  38     /* Since there are few pulses over an entire subframe (i.e. almost
  39        all fc_in[i] are zero) it is faster to loop over fc_in first. */
  40     for(i=0; i<len; i++)
  41     {
  42         if(fc_in[i])
  43         {
  44             for(k=0; k<i; k++)
  45                 fc_out[k] += (fc_in[i] * filter[len + k - i]) >> 15;
  46
  47             for(k=i; k<len; k++)
  48                 fc_out[k] += (fc_in[i] * filter[      k - i]) >> 15;
  49         }
  50     }
  51 }
  52
  53 int ff_celp_lp_synthesis_filter(
  54         int16_t *out,
  55         const int16_t* filter_coeffs,
  56         const int16_t* in,
  57         int buffer_length,
  58         int filter_length,
  59         int stop_on_overflow,
  60         int rounder)
  61 {
  62     int i,n;
  63
  64     // Avoids a +1 in the inner loop.
  65     filter_length++;
  66
  67     for(n=0; n<buffer_length; n++)
  68     {
  69         int sum = rounder;
  70         for(i=1; i<filter_length; i++)
  71             sum -= filter_coeffs[i-1] * out[n-i];
  72
  73         sum = (sum >> 12) + in[n];
  74
  75         if(sum + 0x8000 > 0xFFFFU)
  76         {
  77             if(stop_on_overflow)
  78                 return 1;
  79             sum = (sum >> 31) ^ 32767;
  80         }
  81         out[n] = sum;
  82     }
  83
  84     return 0;
  85 }
  86
  87 void ff_celp_lp_synthesis_filterf(
  88         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     // Avoids a +1 in the inner loop.
  97     filter_length++;
  98
  99     for(n=0; n<buffer_length; n++)
 100     {
 101         out[n] = in[n];
 102         for(i=1; i<filter_length; i++)
 103             out[n] -= filter_coeffs[i-1] * out[n-i];
 104     }
 105 }
 106
 107 void ff_celp_lp_zero_synthesis_filterf(
 108         float *out,
 109         const float* filter_coeffs,
 110         const float* in,
 111         int buffer_length,
 112         int filter_length)
 113 {
 114     int i,n;
 115
 116     // Avoids a +1 in the inner loop.
 117     filter_length++;
 118
 119     for(n=0; n<buffer_length; n++)
 120     {
 121         out[n] = in[n];
 122         for(i=1; i<filter_length; i++)
 123             out[n] -= filter_coeffs[i-1] * in[n-i];
 124     }
 125 }