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