1 /* ------------------------------------------------------------------
2 * Copyright (C) 1998-2009 PacketVideo
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
13 * express or implied.
14 * See the License for the specific language governing permissions
15 * and limitations under the License.
16 * -------------------------------------------------------------------
17 */
18 /*
19 ------------------------------------------------------------------------------
20
21 PacketVideo Corp.
22 MP3 Decoder Library
23
24 Filename: pvmp3_alias_reduction.cpp
25
26 Date: 09/21/2007
27
28 ------------------------------------------------------------------------------
29 REVISION HISTORY
30
31
32 Description:
33
34 ------------------------------------------------------------------------------
35 INPUT AND OUTPUT DEFINITIONS
36
37 Input
38 int32 *input_buffer, Ptr to fequency lines of current channel
39 struct gr_info_s *gr_info, structure with granuke information for the
40 input
41 mp3Header *info mp3 header information
42
43 ------------------------------------------------------------------------------
44 FUNCTION DESCRIPTION
45
46 Alias Reduction
47
48
49
50 Alias reduction before processing by the IMDCT
51
52 Csi +
53 >---------0---------0-------->
54 \ / -
55 Cai \ /
56 \ /
57 \ /
58 \
59 / \
60 Cai / \
61 / \ +
62 >--------0---------0---------->
63 Csi +
64
65 Aliasing Butterfly
66 Alias reduction is not applied to short blocks
67
68 ------------------------------------------------------------------------------
69 REQUIREMENTS
70
71
72 ------------------------------------------------------------------------------
73 REFERENCES
74
75 [1] ISO MPEG Audio Subgroup Software Simulation Group (1996)
76 ISO 13818-3 MPEG-2 Audio Decoder - Lower Sampling Frequency Extension
77
78 ------------------------------------------------------------------------------
79 PSEUDO-CODE
80 1 ci
81 csi = ---------------- csi = ----------------
82 sqrt( 1 + (ci^2)) sqrt( 1 + (ci^2))
83
84
85 ci = -0.6, -0.535, -0.33, -0.185, -0.095, -0.041, -0.0142, -0.0037
86
87 ------------------------------------------------------------------------------
88 */
89
90
91 /*----------------------------------------------------------------------------
92 ; INCLUDES
93 ----------------------------------------------------------------------------*/
94
95 #include "pvmp3_alias_reduction.h"
96 #include "pv_mp3dec_fxd_op.h"
97
98
99 /*----------------------------------------------------------------------------
100 ; MACROS
101 ; Define module specific macros here
102 ----------------------------------------------------------------------------*/
103
104
105 /*----------------------------------------------------------------------------
106 ; DEFINES
107 ; Include all pre-processor statements here. Include conditional
108 ; compile variables also.
109 ----------------------------------------------------------------------------*/
110 #define NUM_BUTTERFLIES 8
111
112 #define Q31_fmt(a) (int32(double(0x7FFFFFFF)*a))
113
114 /*----------------------------------------------------------------------------
115 ; LOCAL FUNCTION DEFINITIONS
116 ; Function Prototype declaration
117 ----------------------------------------------------------------------------*/
118
119 /*----------------------------------------------------------------------------
120 ; LOCAL STORE/BUFFER/POINTER DEFINITIONS
121 ; Variable declaration - defined here and used outside this module
122 ----------------------------------------------------------------------------*/
123 const int32 c_signal [ NUM_BUTTERFLIES ] =
124 {
125
126 Q31_fmt(0.85749292571254f), Q31_fmt(0.88174199731771f),
127 Q31_fmt(0.94962864910273f), Q31_fmt(0.98331459249179f),
128 Q31_fmt(0.99551781606759f), Q31_fmt(0.99916055817815f),
129 Q31_fmt(0.99989919524445f), Q31_fmt(0.99999315507028f)
130
131 };
132
133
134 const int32 c_alias [ NUM_BUTTERFLIES ] =
135 {
136
137 Q31_fmt(-0.51449575542753f), Q31_fmt(-0.47173196856497f),
138 Q31_fmt(-0.31337745420390f), Q31_fmt(-0.18191319961098f),
139 Q31_fmt(-0.09457419252642f), Q31_fmt(-0.04096558288530f),
140 Q31_fmt(-0.01419856857247f), Q31_fmt(-0.00369997467376f)
141 };
142
143 /*----------------------------------------------------------------------------
144 ; EXTERNAL FUNCTION REFERENCES
145 ; Declare functions defined elsewhere and referenced in this module
146 ----------------------------------------------------------------------------*/
147
148 /*----------------------------------------------------------------------------
149 ; EXTERNAL GLOBAL STORE/BUFFER/POINTER REFERENCES
150 ; Declare variables used in this module but defined elsewhere
151 ----------------------------------------------------------------------------*/
152
153 /*----------------------------------------------------------------------------
154 ; FUNCTION CODE
155 ----------------------------------------------------------------------------*/
156
pvmp3_alias_reduction(int32 * input_buffer,granuleInfo * gr_info,int32 * used_freq_lines,mp3Header * info)157 void pvmp3_alias_reduction(int32 *input_buffer, /* Ptr to spec values of current channel */
158 granuleInfo *gr_info,
159 int32 *used_freq_lines,
160 mp3Header *info)
161 {
162 int32 *ptr1;
163 int32 *ptr2;
164 int32 *ptr3;
165 int32 *ptr4;
166 const int32 *ptr_csi;
167 const int32 *ptr_csa;
168 int32 sblim;
169
170 int32 i, j;
171
172 *used_freq_lines = fxp_mul32_Q32(*used_freq_lines << 16, (int32)(0x7FFFFFFF / (float)18 - 1.0f)) >> 15;
173
174
175 if (gr_info->window_switching_flag && gr_info->block_type == 2)
176 {
177 if (gr_info->mixed_block_flag)
178 {
179 sblim = ((info->version_x == MPEG_2_5) && (info->sampling_frequency == 2)) ? 3 : 1;
180 }
181 else
182 {
183 return; /* illegal parameter */
184 }
185 }
186 else
187 {
188 sblim = *used_freq_lines + 1;
189
190 if (sblim > SUBBANDS_NUMBER - 1)
191 {
192 sblim = SUBBANDS_NUMBER - 1; /* default */
193 }
194
195 }
196
197
198 ptr3 = &input_buffer[17];
199 ptr4 = &input_buffer[18];
200 ptr_csi = c_signal;
201 ptr_csa = c_alias;
202
203 /* NUM_BUTTERFLIES (=8) butterflies between each pair of sub-bands*/
204
205 for (i = NUM_BUTTERFLIES >> 1; i != 0; i--)
206 {
207 int32 csi1 = *ptr_csi++;
208 int32 csi2 = *ptr_csi++;
209 int32 csa1 = *ptr_csa++;
210 int32 csa2 = *ptr_csa++;
211
212 ptr1 = ptr3;
213 ptr3 -= 2;
214 ptr2 = ptr4;
215 ptr4 += 2;
216
217 /*
218 * "sblim" alias-reduction operations between each
219 * pair of sub-bands
220 */
221
222 for (j = sblim >> 1; j != 0; j--)
223 {
224 int32 y = *ptr2;
225 int32 x = *ptr1 << 1;
226 *ptr1-- = fxp_msb32_Q32(fxp_mul32_Q32(x, csi1), y << 1, csa1);
227 *ptr2++ = fxp_mac32_Q32(fxp_mul32_Q32(y << 1, csi1), x, csa1);
228 y = *ptr2;
229 x = *ptr1 << 1;
230 *ptr1 = fxp_msb32_Q32(fxp_mul32_Q32(x, csi2), y << 1, csa2);
231 *ptr2 = fxp_mac32_Q32(fxp_mul32_Q32(y << 1, csi2), x, csa2);
232 ptr1 += 19;
233 ptr2 += 17;
234 y = *ptr2;
235 x = *ptr1 << 1;
236 *ptr1-- = fxp_msb32_Q32(fxp_mul32_Q32(x, csi1), y << 1, csa1);
237 *ptr2++ = fxp_mac32_Q32(fxp_mul32_Q32(y << 1, csi1), x, csa1);
238 y = *ptr2;
239 x = *ptr1 << 1;
240 *ptr1 = fxp_msb32_Q32(fxp_mul32_Q32(x, csi2), y << 1, csa2);
241 *ptr2 = fxp_mac32_Q32(fxp_mul32_Q32(y << 1, csi2), x, csa2);
242 ptr1 += 19;
243 ptr2 += 17;
244
245 }
246
247 if (sblim & 1)
248 {
249 int32 x = *ptr1 << 1;
250 int32 y = *ptr2;
251 *ptr1-- = fxp_msb32_Q32(fxp_mul32_Q32(x, csi1), y << 1, csa1);
252 *ptr2++ = fxp_mac32_Q32(fxp_mul32_Q32(y << 1, csi1), x, csa1);
253
254 x = *ptr1 << 1;
255 y = *ptr2;
256 *ptr1 = fxp_msb32_Q32(fxp_mul32_Q32(x, csi2), y << 1, csa2);
257 *ptr2 = fxp_mac32_Q32(fxp_mul32_Q32(y << 1, csi2), x, csa2);
258 }
259 }
260
261 }
262