/*
  * various filters for ACELP-based codecs
  *
  * Copyright (c) 2008 Vladimir Voroshilov
  *
  * This file is part of FFmpeg.
  *
  * FFmpeg is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either
  * version 2.1 of the License, or (at your option) any later version.
  *
  * FFmpeg is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Lesser General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser General Public
  * License along with FFmpeg; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
 #include <inttypes.h>
 
 #include "avcodec.h"
 #include "celp_filters.h"
 
 void ff_celp_convolve_circ(
         int16_t* fc_out,
         const int16_t* fc_in,
         const int16_t* filter,
         int len)
 {
     int i, k;
 
     memset(fc_out, 0, len * sizeof(int16_t));
 
     /* Since there are few pulses over an entire subframe (i.e. almost
        all fc_in[i] are zero) it is faster to loop over fc_in first. */
     for(i=0; i<len; i++)
     {
         if(fc_in[i])
         {
             for(k=0; k<i; k++)
                 fc_out[k] += (fc_in[i] * filter[len + k - i]) >> 15;
 
             for(k=i; k<len; k++)
                 fc_out[k] += (fc_in[i] * filter[      k - i]) >> 15;
         }
     }
 }
 
 int ff_celp_lp_synthesis_filter(
         int16_t *out,
         const int16_t* filter_coeffs,
         const int16_t* in,
         int buffer_length,
         int filter_length,
         int stop_on_overflow,
         int rounder)
 {
     int i,n;
 
     // These two lines are to avoid a -1 subtraction in the main loop
     filter_length++;
     filter_coeffs--;
 
     for(n=0; n<buffer_length; n++)
     {
         int sum = rounder;
         for(i=1; i<filter_length; i++)
             sum -= filter_coeffs[i] * out[n-i];
 
         sum = (sum >> 12) + in[n];
 
         if(sum + 0x8000 > 0xFFFFU)
         {
             if(stop_on_overflow)
                 return 1;
             sum = (sum >> 31) ^ 32767;
         }
         out[n] = sum;
     }
 
     return 0;
 }

 
 void ff_celp_lp_synthesis_filterf(
         float *out,
         const float* filter_coeffs,
         const float* in,
         int buffer_length,
         int filter_length)
 {
     int i,n;
 
     // These two lines are to avoid a -1 subtraction in the main loop
     filter_length++;
     filter_coeffs--;
 
     for(n=0; n<buffer_length; n++)
     {
         out[n] = in[n];
         for(i=1; i<filter_length; i++)

             out[n] -= filter_coeffs[i] * out[n-i];

     }
 }