vp8/common/predictdc.c

   1 /*
   2  *  Copyright (c) 2010 The WebM project authors. All Rights Reserved.
   3  *
   4  *  Use of this source code is governed by a BSD-style license
   5  *  that can be found in the LICENSE file in the root of the source
   6  *  tree. An additional intellectual property rights grant can be found
   7  *  in the file PATENTS.  All contributing project authors may
   8  *  be found in the AUTHORS file in the root of the source tree.
   9  */
  10
  11
  12 #include <stdlib.h>
  13 #include "blockd.h"
  14
  15
  16 void vp8_predict_dc(short *lastdc, short *thisdc, short quant, short *cons)
  17 {
  18     int diff;
  19     int sign;
  20     int last_dc = *lastdc;
  21     int this_dc = *thisdc;
  22
  23     if (*cons  > DCPREDCNTTHRESH)
  24     {
  25         this_dc += last_dc;
  26     }
  27
  28     diff = abs(last_dc - this_dc);
  29     sign  = (last_dc >> 31) ^(this_dc >> 31);
  30     sign |= (!last_dc | !this_dc);
  31
  32     if (sign)
  33     {
  34         *cons = 0;
  35     }
  36     else
  37     {
  38         if (diff <= DCPREDSIMTHRESH * quant)
  39             (*cons)++ ;
  40     }
  41
  42     *thisdc = this_dc;
  43     *lastdc = this_dc;
  44 }