text: /*
   * 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"
  #include "libavutil/avassert.h"
  #include "libavutil/common.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;
          }
      }
  }
  
  void ff_celp_circ_addf(float *out, const float *in,
                         const float *lagged, int lag, float fac, int n)
  {
      int k;
      for (k = 0; k < lag; k++)
          out[k] = in[k] + fac * lagged[n + k - lag];
      for (; k < n; k++)
          out[k] = in[k] + fac * lagged[    k - lag];
  }
  
  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 shift, int rounder)
  {
      int i,n;
  
      for (n = 0; n < buffer_length; n++) {
          int sum = -rounder, sum1;
          for (i = 1; i <= filter_length; i++)
              sum += filter_coeffs[i-1] * out[n-i];
  
          sum1 = ((-sum >> 12) + in[n]) >> shift;
          sum  = av_clip_int16(sum1);
  
          if (stop_on_overflow && sum != sum1)
              return 1;
  
          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;
  
  #if 0 // Unoptimized code path for improved readability
      for (n = 0; n < buffer_length; n++) {
          out[n] = in[n];
          for (i = 1; i <= filter_length; i++)
              out[n] -= filter_coeffs[i-1] * out[n-i];
      }
  #else
      float out0, out1, out2, out3;
      float old_out0, old_out1, old_out2, old_out3;
      float a,b,c;
  
      a = filter_coeffs[0];
      b = filter_coeffs[1];
      c = filter_coeffs[2];
      b -= filter_coeffs[0] * filter_coeffs[0];
      c -= filter_coeffs[1] * filter_coeffs[0];
      c -= filter_coeffs[0] * b;
  
      av_assert2((filter_length&1)==0 && filter_length>=4);
  
      old_out0 = out[-4];
      old_out1 = out[-3];
      old_out2 = out[-2];
      old_out3 = out[-1];
      for (n = 0; n <= buffer_length - 4; n+=4) {
          float tmp0,tmp1,tmp2;
          float val;
  
          out0 = in[0];
          out1 = in[1];
          out2 = in[2];
          out3 = in[3];
  
          out0 -= filter_coeffs[2] * old_out1;
          out1 -= filter_coeffs[2] * old_out2;
          out2 -= filter_coeffs[2] * old_out3;
  
          out0 -= filter_coeffs[1] * old_out2;
          out1 -= filter_coeffs[1] * old_out3;
  
          out0 -= filter_coeffs[0] * old_out3;
  
          val = filter_coeffs[3];
  
          out0 -= val * old_out0;
          out1 -= val * old_out1;
          out2 -= val * old_out2;
          out3 -= val * old_out3;
  
          for (i = 5; i < filter_length; i += 2) {
              old_out3 = out[-i];
              val = filter_coeffs[i-1];
  
              out0 -= val * old_out3;
              out1 -= val * old_out0;
              out2 -= val * old_out1;
              out3 -= val * old_out2;
  
              old_out2 = out[-i-1];
  
              val = filter_coeffs[i];
  
              out0 -= val * old_out2;
              out1 -= val * old_out3;
              out2 -= val * old_out0;
              out3 -= val * old_out1;
  
              FFSWAP(float, old_out0, old_out2);
              old_out1 = old_out3;
          }
  
          tmp0 = out0;
          tmp1 = out1;
          tmp2 = out2;
  
          out3 -= a * tmp2;
          out2 -= a * tmp1;
          out1 -= a * tmp0;
  
          out3 -= b * tmp1;
          out2 -= b * tmp0;
  
          out3 -= c * tmp0;
  
  
          out[0] = out0;
          out[1] = out1;
          out[2] = out2;
          out[3] = out3;
  
          old_out0 = out0;
          old_out1 = out1;
          old_out2 = out2;
          old_out3 = out3;
  
          out += 4;
          in  += 4;
      }
  
      out -= n;
      in -= n;
      for (; n < buffer_length; n++) {
          out[n] = in[n];
          for (i = 1; i <= filter_length; i++)
              out[n] -= filter_coeffs[i-1] * out[n-i];
      }
  #endif
  }
  
  void ff_celp_lp_zero_synthesis_filterf(float *out, const float *filter_coeffs,
                                         const float *in, int buffer_length,
                                         int filter_length)
  {
      int i,n;
  
      for (n = 0; n < buffer_length; n++) {
          out[n] = in[n];
          for (i = 1; i <= filter_length; i++)
              out[n] += filter_coeffs[i-1] * in[n-i];
      }
  }
  
  void ff_celp_filter_init(CELPFContext *c)
  {
      c->celp_lp_synthesis_filterf        = ff_celp_lp_synthesis_filterf;
      c->celp_lp_zero_synthesis_filterf   = ff_celp_lp_zero_synthesis_filterf;
  
      if(HAVE_MIPSFPU)
          ff_celp_filter_init_mips(c);
  }
  