Tristan Matthews | 0a329cc | 2013-07-17 13:20:14 -0400 | [diff] [blame] | 1 | |
| 2 | /****************************************************************** |
| 3 | |
| 4 | iLBC Speech Coder ANSI-C Source Code |
| 5 | |
| 6 | |
| 7 | |
| 8 | |
| 9 | |
| 10 | |
| 11 | gainquant.c |
| 12 | |
| 13 | Copyright (C) The Internet Society (2004). |
| 14 | All Rights Reserved. |
| 15 | |
| 16 | ******************************************************************/ |
| 17 | |
| 18 | #include <string.h> |
| 19 | #include <math.h> |
| 20 | #include "constants.h" |
| 21 | #include "filter.h" |
| 22 | |
| 23 | /*----------------------------------------------------------------* |
| 24 | * quantizer for the gain in the gain-shape coding of residual |
| 25 | *---------------------------------------------------------------*/ |
| 26 | |
| 27 | float gainquant(/* (o) quantized gain value */ |
| 28 | float in, /* (i) gain value */ |
| 29 | float maxIn,/* (i) maximum of gain value */ |
| 30 | int cblen, /* (i) number of quantization indices */ |
| 31 | int *index /* (o) quantization index */ |
| 32 | ){ |
| 33 | int i, tindex; |
| 34 | float minmeasure,measure, *cb, scale; |
| 35 | |
| 36 | /* ensure a lower bound on the scaling factor */ |
| 37 | |
| 38 | scale=maxIn; |
| 39 | |
| 40 | if (scale<0.1) { |
| 41 | scale=(float)0.1; |
| 42 | } |
| 43 | |
| 44 | /* select the quantization table */ |
| 45 | |
| 46 | if (cblen == 8) { |
| 47 | cb = gain_sq3Tbl; |
| 48 | } else if (cblen == 16) { |
| 49 | cb = gain_sq4Tbl; |
| 50 | } else { |
| 51 | cb = gain_sq5Tbl; |
| 52 | } |
| 53 | |
| 54 | /* select the best index in the quantization table */ |
| 55 | |
| 56 | minmeasure=10000000.0; |
| 57 | tindex=0; |
| 58 | for (i=0; i<cblen; i++) { |
| 59 | |
| 60 | |
| 61 | |
| 62 | |
| 63 | |
| 64 | measure=(in-scale*cb[i])*(in-scale*cb[i]); |
| 65 | |
| 66 | if (measure<minmeasure) { |
| 67 | tindex=i; |
| 68 | minmeasure=measure; |
| 69 | } |
| 70 | } |
| 71 | *index=tindex; |
| 72 | |
| 73 | /* return the quantized value */ |
| 74 | |
| 75 | return scale*cb[tindex]; |
| 76 | } |
| 77 | |
| 78 | /*----------------------------------------------------------------* |
| 79 | * decoder for quantized gains in the gain-shape coding of |
| 80 | * residual |
| 81 | *---------------------------------------------------------------*/ |
| 82 | |
| 83 | float gaindequant( /* (o) quantized gain value */ |
| 84 | int index, /* (i) quantization index */ |
| 85 | float maxIn,/* (i) maximum of unquantized gain */ |
| 86 | int cblen /* (i) number of quantization indices */ |
| 87 | ){ |
| 88 | float scale; |
| 89 | |
| 90 | /* obtain correct scale factor */ |
| 91 | |
| 92 | scale=(float)fabs(maxIn); |
| 93 | |
| 94 | if (scale<0.1) { |
| 95 | scale=(float)0.1; |
| 96 | } |
| 97 | |
| 98 | /* select the quantization table and return the decoded value */ |
| 99 | |
| 100 | if (cblen==8) { |
| 101 | return scale*gain_sq3Tbl[index]; |
| 102 | } else if (cblen==16) { |
| 103 | return scale*gain_sq4Tbl[index]; |
| 104 | } |
| 105 | else if (cblen==32) { |
| 106 | return scale*gain_sq5Tbl[index]; |
| 107 | } |
| 108 | |
| 109 | return 0.0; |
| 110 | } |
| 111 | |
| 112 | |
| 113 | |
| 114 | |
| 115 | |
| 116 | |