| /* ------------------------------------------------------------------ |
| * 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 */ |
