/* ------------------------------------------------------------------ * 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: lt_decode.c ------------------------------------------------------------------------------ REVISION HISTORY Description: Modified from original shareware code Description: Modified to pass variables by reference to eliminate use of global variables. Description: First round of optimizations. Description: pInputStream is now the 2nd parameter to this function. Description: Changed to work with MT's new get_ics_info.c function, which only calls lt_decode if LTP is enabled. This removes one grab from the bitstream and one "if" from this code. Also, changed setting of weight. Now, rather than setting the actual weight, I only set the index into a table in this function. Description: Replace some instances of getbits to get9_n_lessbits when the number of bits read is 9 or less and get1bits when only 1 bit is read. Who: Date: Description: ------------------------------------------------------------------------------ INPUT AND OUTPUT DEFINITIONS Inputs: win_type Type of window (SHORT or LONG) [WINDOW_TYPE] max_sfb Maximum number of active scalefactor bands [Int] pLt_pred Pointer to structure containing information for long-term prediction. [LT_PRED_STATUS *] pInputStream Pointer to structure containing bitstream information. [BITS *] Local Stores/Buffers/Pointers Needed: None Global Stores/Buffers/Pointers Needed: None Outputs: None Pointers and Buffers Modified: pLt_pred->weight_index - updated with index into weight table for LTP. Local Stores Modified: None Global Stores Modified: None ------------------------------------------------------------------------------ FUNCTION DESCRIPTION This function decodes the bitstream elements for long term prediction ------------------------------------------------------------------------------ REQUIREMENTS ------------------------------------------------------------------------------ REFERENCES (1) MPEG-2 NBC Audio Decoder "This software module was originally developed by Nokia in the course of development of the MPEG-2 AAC/MPEG-4 Audio standard ISO/IEC13818-7, 14496-1, 2 and 3. This software module is an implementation of a part of one or more MPEG-2 AAC/MPEG-4 Audio tools as specified by the MPEG-2 aac/MPEG-4 Audio standard. ISO/IEC gives users of the MPEG-2aac/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 aac/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, 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 aac/MPEG-4 Audio conforming products. The original developer retains full right to use the code for the developer's own purpose, assign or donate the code to a third party and to inhibit third party from using the code for non MPEG-2 aac/MPEG-4 Audio conforming products. This copyright notice must be included in all copies or derivative works." Copyright (c)1997. ------------------------------------------------------------------------------ PSEUDO-CODE pDelay[0] = (Int) getbits( LEN_LTP_LAG, pInputStream); temp_reg = (Int) getbits( LEN_LTP_COEF, pInputStream); pLt_pred->weight = codebook[temp_reg]; last_band = max_sfb; IF (win_type != EIGHT_SHORT_SEQUENCE) IF (last_band > MAX_LT_PRED_LONG_SFB) last_band = MAX_LT_PRED_LONG_SFB; ENDIF FOR (m = last_band; m > 0; m--) *(pSfbPredictionUsed++) = (Int) getbits( LEN_LTP_LONG_USED, pInputStream); ENDFOR FOR (m = (max_sfb - last_band); m > 0; m--) *(pSfbPredictionUsed++) = 0; ENDFOR ELSE IF (last_band > MAX_LT_PRED_SHORT_SFB) last_band = MAX_LT_PRED_SHORT_SFB; ENDIF prev_subblock = pDelay[0]; pWinPredictionUsed++; pTempPtr = &pSfbPredictionUsed[0]; FOR (m = NUM_SHORT_WINDOWS; m > 0;) m--; temp_reg = (Int) getbits( LEN_LTP_SHORT_USED, pInputStream); *(pWinPredictionUsed++) = temp_reg; IF (temp_reg != FALSE) { *(pDelay++) = prev_subblock; FOR (k = last_band; k > 0; k--) { *(pTempPtr++) = 1; } break; ELSE { pDelay++; pTempPtr += last_band; } ENDFOR (m = NUM_SHORT_WINDOWS; m > 0;) prev_subblock += LTP_LAG_OFFSET; FOR (; m > 0; m--) temp_reg = (Int) getbits ( LEN_LTP_SHORT_USED, pInputStream); *(pWinPredictionUsed++) = temp_reg; IF (temp_reg != FALSE) temp_reg = (Int) getbits( LEN_LTP_SHORT_LAG_PRESENT, pInputStream); IF (temp_reg != 0) temp_reg = (Int) getbits( LEN_LTP_SHORT_LAG, pInputStream); *(pDelay++) = prev_subblock - temp_reg; ELSE *(pDelay++) = prev_subblock - LTP_LAG_OFFSET; ENDIF FOR (k = last_band; k > 0; k--) *(pTempPtr++) = 1; ENDFOR ELSE pDelay++; pTempPtr += last_band; ENDIF ENDFOR (; m > 0; m--) ENDIF (win_type != EIGHT_SHORT_SEQUENCE) ------------------------------------------------------------------------------ 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 "lt_decode.h" #include "ltp_common_internal.h" #include "window_block_fxp.h" #include "e_window_sequence.h" #include "s_lt_pred_status.h" #include "s_bits.h" #include "ibstream.h" /*---------------------------------------------------------------------------- ; MACROS ; Define module specific macros here ----------------------------------------------------------------------------*/ /*---------------------------------------------------------------------------- ; DEFINES ; Include all pre-processor statements here. Include conditional ; compile variables also. ----------------------------------------------------------------------------*/ /*---------------------------------------------------------------------------- ; 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 lt_decode( const WINDOW_SEQUENCE win_type, BITS *pInputStream, const Int max_sfb, LT_PRED_STATUS *pLt_pred) { Int wnd_num; Int k; Int last_band; Int prev_subblock; Int prev_subblock_nonzero; Int temp_reg; Bool *pWinPredictionUsed = pLt_pred->win_prediction_used; Bool *pSfbPredictionUsed = pLt_pred->sfb_prediction_used; Int *pTempPtr; Int *pDelay = pLt_pred->delay; pDelay[0] = (Int) get17_n_lessbits( LEN_LTP_LAG, /* 11 bits */ pInputStream); pLt_pred->weight_index = (Int) get9_n_lessbits( LEN_LTP_COEF, /* 3 bits */ pInputStream); last_band = max_sfb; if (win_type != EIGHT_SHORT_SEQUENCE) { /* last_band = min(MAX_LT_PRED_LONG_SFB, max_sfb) MAX_SCFAC_BANDS */ if (last_band > MAX_LT_PRED_LONG_SFB) { last_band = MAX_LT_PRED_LONG_SFB; } for (k = last_band; k > 0; k--) { *(pSfbPredictionUsed++) = (Int) get1bits(pInputStream); } /* * This is not a call to memset, because * (max_sfb - last_band) should typically be a small value. */ for (k = (max_sfb - last_band); k > 0; k--) { *(pSfbPredictionUsed++) = FALSE; } } else /* (win_type == EIGHT_SHORT_SEQUENCE) */ { /* last_band = min(MAX_LT_PRED_SHORT_SFB, max_sfb) */ if (last_band > MAX_LT_PRED_SHORT_SFB) { last_band = MAX_LT_PRED_SHORT_SFB; } /* * The following two coding constructs are equivalent... * * first_time == 1 * for (wnd_num=NUM_SHORT_WINDOWS; wnd_num > 0; wnd_num--) * { * if (condition) * { * if (first_time == 1) * { * CODE SECTION A * first_time = 0; * } * else * { * CODE SECTION B * } * } * } * * -----------------------------------EQUIVALENT TO------------ * * wnd_num=NUM_SHORT_WINDOWS; * * do * { * wnd_num--; * if (condition) * { * CODE SECTION A * break; * } * } while( wnd_num > 0) * * while (wnd_num > 0) * { * if (condition) * { * CODE SECTION B * } * wnd_num--; * } * */ prev_subblock = pDelay[0]; pTempPtr = &pSfbPredictionUsed[0]; wnd_num = NUM_SHORT_WINDOWS; prev_subblock_nonzero = prev_subblock; prev_subblock += LTP_LAG_OFFSET; do { /* * Place decrement of wnd_num here, to insure * that the decrement occurs before the * break out of the do-while loop. */ wnd_num--; temp_reg = (Int) get1bits(pInputStream); *(pWinPredictionUsed++) = temp_reg; if (temp_reg != FALSE) { *(pDelay++) = prev_subblock_nonzero; for (k = last_band; k > 0; k--) { *(pTempPtr++) = TRUE; } for (k = (max_sfb - last_band); k > 0; k--) { *(pTempPtr++) = FALSE; } break; } /* if(pWinPredictionUsed) */ else { pDelay++; pTempPtr += max_sfb; } } while (wnd_num > 0); /* * This while loop picks up where the previous one left off. * Notice that the code functions differently inside the loop */ while (wnd_num > 0) { temp_reg = (Int) get1bits(pInputStream); *(pWinPredictionUsed++) = temp_reg; if (temp_reg != FALSE) { temp_reg = (Int) get1bits(pInputStream); if (temp_reg != 0) { temp_reg = (Int) get9_n_lessbits( LEN_LTP_SHORT_LAG, pInputStream); *(pDelay++) = prev_subblock - temp_reg; } else { *(pDelay++) = prev_subblock_nonzero; } for (k = last_band; k > 0; k--) { *(pTempPtr++) = TRUE; } for (k = (max_sfb - last_band); k > 0; k--) { *(pTempPtr++) = FALSE; } } /* if (temp_reg) */ else { pDelay++; pTempPtr += max_sfb; } wnd_num--; } /* while(wnd_num) */ } /* else (win_type == EIGHT_SHORT_SEQUENCE) */ } /* lt_decode */