1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
|
/* ------------------------------------------------------------------
* Copyright (C) 1998-2009 PacketVideo
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
* express or implied.
* See the License for the specific language governing permissions
* and limitations under the License.
* -------------------------------------------------------------------
*/
/*
Pathname: getgroup.c
------------------------------------------------------------------------------
REVISION HISTORY
Description: Modified from original shareware code
Description: Modified to pass variables by reference to eliminate use
of global variables.
Description: (1) Modified to bring code in-line with PV standards
(2) Eliminated if(first_short) statement, move for-loop
inside if statement
(3) Modified UChar -> Int on data types of group
Description: Replace some instances of getbits to get9_n_lessbits
when the number of bits read is 9 or less.
Who: Date: MM/DD/YYYY
Description:
------------------------------------------------------------------------------
INPUT AND OUTPUT DEFINITIONS
Inputs:
pInputStream = pointer to structure that holds input bitstream
information. Type BITS
group[] = array that holds the index of the first window in each
group. Type Int
Local Stores/Buffers/Pointers Needed:
None
Global Stores/Buffers/Pointers Needed:
None
Outputs:
None
Pointers and Buffers Modified:
group contains the index of first windows in each group
Local Stores Modified:
None
Global Stores Modified:
None
------------------------------------------------------------------------------
FUNCTION DESCRIPTION
This function reads the window grouping information associated with an
Individual Channel Stream (ICS). If the window sequence is
EIGHT_SHORT_SEQUENCE, scalefactor grouping information is transmitted. If a
set of short windows form a group then they share scalefactors, intensity
positions and PNS information. The first short window is always a new group
so no grouping bit is transmitted. Subsequent short windows are in the same
group if the associated grouping bit is 1. A new group is started if the
associated grouping bit is 0.
The pointer pGroup points to an array that stores the first window index
of next group. For example, if the window grouping is:
window index: | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 |
grouping : |<- 0 ->| 1 |<- 2 ->|<- 3 ->|
Then:
group[] : | 2 | 3 | 6 | 8 |
------------------------------------------------------------------------------
REQUIREMENTS
This function should replace the contents of the array pointed to by pGroup
with the first window indexes of groups starting from the second group.
------------------------------------------------------------------------------
REFERENCES
(1) MPEG-2 NBC Audio Decoder
"This software module was originally developed by AT&T, Dolby
Laboratories, Fraunhofer Gesellschaft IIS in the course of development
of the MPEG-2 NBC/MPEG-4 Audio standard ISO/IEC 13818-7, 14496-1,2 and
3. This software module is an implementation of a part of one or more
MPEG-2 NBC/MPEG-4 Audio tools as specified by the MPEG-2 NBC/MPEG-4
Audio standard. ISO/IEC gives users of the MPEG-2 NBC/MPEG-4 Audio
standards free license to this software module or modifications thereof
for use in hardware or software products claiming conformance to the
MPEG-2 NBC/MPEG-4 Audio standards. Those intending to use this software
module in hardware or software products are advised that this use may
infringe existing patents. The original developer of this software
module and his/her company, the subsequent editors and their companies,
and ISO/IEC have no liability for use of this software module or
modifications thereof in an implementation. Copyright is not released
for non MPEG-2 NBC/MPEG-4 Audio conforming products.The original
developer retains full right to use the code for his/her own purpose,
assign or donate the code to a third party and to inhibit third party
from using the code for non MPEG-2 NBC/MPEG-4 Audio conforming products.
This copyright notice must be included in all copies or derivative
works."
Copyright(c)1996.
(2) ISO/IEC 14496-3: 1999(E)
Subpart 4
p16 (Table 4.4.6)
p55 (Recovering ics_info)
------------------------------------------------------------------------------
PSEUDO-CODE
IF (pFrameInfo->coef_per_win[0] > SN2)
*pGroup++ = 1;
*pGroup = 1;
ELSE
FOR (win = 1; win < pFrameInfo->num_win; win++)
IF (getbits(1,pInputStream) == 0)
*pGroup++ = win;
ENDIF
ENDFOR (win)
*pGroup = win;
ENDIF(pFrameInfo)
------------------------------------------------------------------------------
RESOURCES USED
When the code is written for a specific target processor the
the resources used should be documented below.
STACK USAGE: [stack count for this module] + [variable to represent
stack usage for each subroutine called]
where: [stack usage variable] = stack usage for [subroutine
name] (see [filename].ext)
DATA MEMORY USED: x words
PROGRAM MEMORY USED: x words
CLOCK CYCLES: [cycle count equation for this module] + [variable
used to represent cycle count for each subroutine
called]
where: [cycle count variable] = cycle count for [subroutine
name] (see [filename].ext)
------------------------------------------------------------------------------
*/
/*----------------------------------------------------------------------------
; INCLUDES
----------------------------------------------------------------------------*/
#include "pv_audio_type_defs.h"
#include "huffman.h"
/*----------------------------------------------------------------------------
; MACROS
; Define module specific macros here
----------------------------------------------------------------------------*/
/*----------------------------------------------------------------------------
; DEFINES
; Include all pre-processor statements here. Include conditional
; compile variables also.
----------------------------------------------------------------------------*/
#define SEVEN 7
/*----------------------------------------------------------------------------
; LOCAL FUNCTION DEFINITIONS
; Function Prototype declaration
----------------------------------------------------------------------------*/
/*----------------------------------------------------------------------------
; LOCAL STORE/BUFFER/POINTER DEFINITIONS
; Variable declaration - defined here and used outside this module
----------------------------------------------------------------------------*/
/*----------------------------------------------------------------------------
; EXTERNAL FUNCTION REFERENCES
; Declare functions defined elsewhere and referenced in this module
----------------------------------------------------------------------------*/
/*----------------------------------------------------------------------------
; EXTERNAL GLOBAL STORE/BUFFER/POINTER REFERENCES
; Declare variables used in this module but defined elsewhere
----------------------------------------------------------------------------*/
/*----------------------------------------------------------------------------
; FUNCTION CODE
----------------------------------------------------------------------------*/
void getgroup(
Int group[],
BITS *pInputStream)
{
Int win;
Int *pGroup;
UInt mask;
UInt groupBits;
pGroup = group;
mask = 0x40;
/* only short-window sequences are grouped!
* first short window is always a new group,
* start reading bitstream from the second
* window, a new group is indicated by an
* "0" bit in the input stream
*/
groupBits =
get9_n_lessbits(
SEVEN,
pInputStream);
for (win = 1; win < NUM_SHORT_WINDOWS; win++)
{
if ((groupBits & mask) == 0)
{
*pGroup++ = win;
} /* if (groupBits) */
mask >>= 1;
} /* for (win) */
*pGroup = win;
} /* getgroup */
|
