/* ------------------------------------------------------------------ * 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 */