1/* Copyright (c) 2011 Xiph.Org Foundation, Skype Limited
2   Written by Jean-Marc Valin and Koen Vos */
3/*
4   Redistribution and use in source and binary forms, with or without
5   modification, are permitted provided that the following conditions
6   are met:
7
8   - Redistributions of source code must retain the above copyright
9   notice, this list of conditions and the following disclaimer.
10
11   - Redistributions in binary form must reproduce the above copyright
12   notice, this list of conditions and the following disclaimer in the
13   documentation and/or other materials provided with the distribution.
14
15   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
16   ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
17   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
18   A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
19   OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
20   EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
21   PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
22   PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
23   LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
24   NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
25   SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
26*/
27
28#ifdef HAVE_CONFIG_H
29#include "config.h"
30#endif
31
32#include "opus.h"
33#include "opus_private.h"
34
35#ifndef DISABLE_FLOAT_API
36OPUS_EXPORT void opus_pcm_soft_clip(float *_x, int N, int C, float *declip_mem)
37{
38   int c;
39   int i;
40   float *x;
41
42   /* First thing: saturate everything to +/- 2 which is the highest level our
43      non-linearity can handle. At the point where the signal reaches +/-2,
44      the derivative will be zero anyway, so this doesn't introduce any
45      discontinuity in the derivative. */
46   for (i=0;i<N*C;i++)
47      _x[i] = MAX16(-2.f, MIN16(2.f, _x[i]));
48   for (c=0;c<C;c++)
49   {
50      float a;
51      float x0;
52      int curr;
53
54      x = _x+c;
55      a = declip_mem[c];
56      /* Continue applying the non-linearity from the previous frame to avoid
57         any discontinuity. */
58      for (i=0;i<N;i++)
59      {
60         if (x[i*C]*a>=0)
61            break;
62         x[i*C] = x[i*C]+a*x[i*C]*x[i*C];
63      }
64
65      curr=0;
66      x0 = x[0];
67      while(1)
68      {
69         int start, end;
70         float maxval;
71         int special=0;
72         int peak_pos;
73         for (i=curr;i<N;i++)
74         {
75            if (x[i*C]>1 || x[i*C]<-1)
76               break;
77         }
78         if (i==N)
79         {
80            a=0;
81            break;
82         }
83         peak_pos = i;
84         start=end=i;
85         maxval=ABS16(x[i*C]);
86         /* Look for first zero crossing before clipping */
87         while (start>0 && x[i*C]*x[(start-1)*C]>=0)
88            start--;
89         /* Look for first zero crossing after clipping */
90         while (end<N && x[i*C]*x[end*C]>=0)
91         {
92            /* Look for other peaks until the next zero-crossing. */
93            if (ABS16(x[end*C])>maxval)
94            {
95               maxval = ABS16(x[end*C]);
96               peak_pos = end;
97            }
98            end++;
99         }
100         /* Detect the special case where we clip before the first zero crossing */
101         special = (start==0 && x[i*C]*x[0]>=0);
102
103         /* Compute a such that maxval + a*maxval^2 = 1 */
104         a=(maxval-1)/(maxval*maxval);
105         if (x[i*C]>0)
106            a = -a;
107         /* Apply soft clipping */
108         for (i=start;i<end;i++)
109            x[i*C] = x[i*C]+a*x[i*C]*x[i*C];
110
111         if (special && peak_pos>=2)
112         {
113            /* Add a linear ramp from the first sample to the signal peak.
114               This avoids a discontinuity at the beginning of the frame. */
115            float delta;
116            float offset = x0-x[0];
117            delta = offset / peak_pos;
118            for (i=curr;i<peak_pos;i++)
119            {
120               offset -= delta;
121               x[i*C] += offset;
122               x[i*C] = MAX16(-1.f, MIN16(1.f, x[i*C]));
123            }
124         }
125         curr = end;
126         if (curr==N)
127            break;
128      }
129      declip_mem[c] = a;
130   }
131}
132#endif
133
134int encode_size(int size, unsigned char *data)
135{
136   if (size < 252)
137   {
138      data[0] = size;
139      return 1;
140   } else {
141      data[0] = 252+(size&0x3);
142      data[1] = (size-(int)data[0])>>2;
143      return 2;
144   }
145}
146
147