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     // These two lines are to avoid a -1 subtraction in the main loop
  65     filter_length++;
  66     filter_coeffs--;
  67
  68     for(n=0; n<buffer_length; n++)
  69     {
  70         int sum = rounder;
  71         for(i=1; i<filter_length; i++)
  72             sum -= filter_coeffs[i] * out[n-i];
  73
  74         sum = (sum >> 12) + in[n];
  75
  76         if(sum + 0x8000 > 0xFFFFU)
  77         {
  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(
  89         float *out,
  90         const float* filter_coeffs,
  91         const float* in,
  92         int buffer_length,
  93         int filter_length)
  94 {
  95     int i,n;
  96
  97     // These two lines are to avoid a -1 subtraction in the main loop
  98     filter_length++;
  99     filter_coeffs--;
 100
 101     for(n=0; n<buffer_length; n++)
 102     {
 103         out[n] = in[n];
 104         for(i=1; i<filter_length; i++)
 105             out[n] += filter_coeffs[i] * out[n-i];
 106     }
 107 }