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261
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1 /*
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2 * Mpeg Layer-1 audio decoder
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3 * --------------------------
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4 * copyright (c) 1995 by Michael Hipp, All rights reserved. See also 'README'
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5 * near unoptimzed ...
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6 *
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7 * may have a few bugs after last optimization ...
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8 *
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9 */
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10
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11 #include "mpg123_sdlsound.h"
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12
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13 void I_step_one(unsigned int balloc[], unsigned int scale_index[2][SBLIMIT],struct frame *fr)
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14 {
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15 unsigned int *ba=balloc;
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16 unsigned int *sca = (unsigned int *) scale_index;
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17
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18 if(fr->stereo) {
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19 int i;
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20 int jsbound = fr->jsbound;
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21 for (i=0;i<jsbound;i++) {
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22 *ba++ = getbits(4);
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23 *ba++ = getbits(4);
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24 }
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25 for (i=jsbound;i<SBLIMIT;i++)
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26 *ba++ = getbits(4);
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27
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28 ba = balloc;
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29
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30 for (i=0;i<jsbound;i++) {
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31 if ((*ba++))
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32 *sca++ = getbits(6);
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33 if ((*ba++))
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34 *sca++ = getbits(6);
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35 }
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36 for (i=jsbound;i<SBLIMIT;i++)
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37 if ((*ba++)) {
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38 *sca++ = getbits(6);
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39 *sca++ = getbits(6);
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40 }
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41 }
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42 else {
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43 int i;
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44 for (i=0;i<SBLIMIT;i++)
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45 *ba++ = getbits(4);
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46 ba = balloc;
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47 for (i=0;i<SBLIMIT;i++)
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48 if ((*ba++))
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49 *sca++ = getbits(6);
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50 }
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51 }
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52
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53 void I_step_two(real fraction[2][SBLIMIT],unsigned int balloc[2*SBLIMIT],
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54 unsigned int scale_index[2][SBLIMIT],struct frame *fr)
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55 {
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56 int i,n;
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57 int smpb[2*SBLIMIT]; /* values: 0-65535 */
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58 int *sample;
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59 register unsigned int *ba;
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60 register unsigned int *sca = (unsigned int *) scale_index;
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61
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62 if(fr->stereo) {
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63 int jsbound = fr->jsbound;
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64 register real *f0 = fraction[0];
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65 register real *f1 = fraction[1];
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66 ba = balloc;
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67 for (sample=smpb,i=0;i<jsbound;i++) {
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68 if ((n = *ba++))
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69 *sample++ = getbits(n+1);
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70 if ((n = *ba++))
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71 *sample++ = getbits(n+1);
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72 }
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73 for (i=jsbound;i<SBLIMIT;i++)
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74 if ((n = *ba++))
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75 *sample++ = getbits(n+1);
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76
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77 ba = balloc;
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78 for (sample=smpb,i=0;i<jsbound;i++) {
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79 if((n=*ba++))
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80 *f0++ = (real) ( ((-1)<<n) + (*sample++) + 1) * muls[n+1][*sca++];
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81 else
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82 *f0++ = 0.0;
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83 if((n=*ba++))
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84 *f1++ = (real) ( ((-1)<<n) + (*sample++) + 1) * muls[n+1][*sca++];
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85 else
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86 *f1++ = 0.0;
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87 }
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88 for (i=jsbound;i<SBLIMIT;i++) {
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89 if ((n=*ba++)) {
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90 real samp = ( ((-1)<<n) + (*sample++) + 1);
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91 *f0++ = samp * muls[n+1][*sca++];
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92 *f1++ = samp * muls[n+1][*sca++];
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93 }
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94 else
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95 *f0++ = *f1++ = 0.0;
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96 }
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97 }
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98 else {
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99 register real *f0 = fraction[0];
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100 ba = balloc;
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101 for (sample=smpb,i=0;i<SBLIMIT;i++)
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102 if ((n = *ba++))
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103 *sample++ = getbits(n+1);
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104 ba = balloc;
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105 for (sample=smpb,i=0;i<SBLIMIT;i++) {
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106 if((n=*ba++))
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107 *f0++ = (real) ( ((-1)<<n) + (*sample++) + 1) * muls[n+1][*sca++];
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108 else
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109 *f0++ = 0.0;
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110 }
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111 }
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112 }
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113
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114 int do_layer1(struct frame *fr,unsigned char *pcm_sample,int *pcm_point)
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115 {
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116 int clip=0;
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117 int i,stereo = fr->stereo;
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118 unsigned int balloc[2*SBLIMIT];
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119 unsigned int scale_index[2][SBLIMIT];
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120 real fraction[2][SBLIMIT];
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121 int single = fr->single;
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122
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123 fr->jsbound = (fr->mode == MPG_MD_JOINT_STEREO) ? (fr->mode_ext<<2)+4 : 32;
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124
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125 if(stereo == 1 || single == 3)
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126 single = 0;
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127
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128 I_step_one(balloc,scale_index,fr);
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129
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130 for (i=0;i<SCALE_BLOCK;i++)
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131 {
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132 I_step_two(fraction,balloc,scale_index,fr);
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133
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134 if(single >= 0) {
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135 clip += synth_1to1_mono( (real*)fraction[single],pcm_sample,pcm_point);
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136 }
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137 else {
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138 int p1 = *pcm_point;
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139 clip += synth_1to1( (real*)fraction[0],0,pcm_sample,&p1);
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140 clip += synth_1to1( (real*)fraction[1],1,pcm_sample,pcm_point);
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141 }
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142 }
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143
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144 return clip;
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145 }
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146
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147
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