| /* ------------------------------------------------------------------ |
| * 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: tns_decode_coef.c |
| |
| ------------------------------------------------------------------------------ |
| REVISION HISTORY |
| |
| Description: Modified from original shareware code |
| |
| Description: Implemented in 16-bit Fixed Point |
| |
| Description: Implemented in 24-bit Fixed Point |
| |
| Description: Modified to return the calculated LPC coefficients "in place" |
| This saves memory, cycles, etc. because it saves a large temporary |
| array being declared on the stack in another function (tns_setup_filter) |
| |
| Description: Modified to return the q-format of the lpc coefficients. |
| |
| Description: Modified for more reliable overflow protection. tns_decode_coef |
| no longer relies on "reasonable" outputs. This code should handle all |
| possible inputs. |
| |
| Description: Modified per review comments. |
| |
| Description: Added check condition to avoid numbers with a Q bigger than |
| 15 from being passed, otherwise in a 16-bit number the sign is lost. |
| |
| Description: Modified to utilize scratch memory techniques, thereby |
| eliminating two arrays of size TNS_MAX_ORDER, which were previously declared |
| on the stack. |
| |
| Description: Updated the SW template to include the full pathname to the |
| source file and a slightly modified copyright header. |
| |
| Description: |
| (1) Changed the order of the unsigned * signed multiply so the |
| casting to Int32 is performed on the unsigned operand. |
| |
| (2) Removed some unnecessary casting. |
| (3) Fixed a problem where a 16-bit value was casted to 32-bits AFTER |
| a shift. It should have been cast to 32-bits BEFORE the shifting. |
| |
| |
| Description: modified precision of coefficients |
| |
| Who: Date: |
| Description: |
| ------------------------------------------------------------------------------ |
| INPUT AND OUTPUT DEFINITIONS |
| |
| The inputs and their range are defined in ISO/IEC 14496-3:1999(E) |
| Part 3 MPEG-4 Audio |
| Subpart 4 |
| |
| Inputs: order = RANGE = 1-20 |
| const Int |
| |
| coef_res = RANGE = 0-1 |
| const Int |
| |
| lpc_coef = RANGE = -8 to 7 if coef_res = 1 compression OFF |
| -4 to 3 if coef_res = 1 compression ON |
| -4 to 3 if coef_res = 0 compression OFF |
| -2 to 1 if coef_res = 0 compression ON |
| |
| [Int *, length TNS_MAX_ORDER] |
| |
| Global Stores/Buffers/Pointers Needed: |
| None |
| |
| Outputs: |
| q_lpc = q_format for the calculated LPC coefs. |
| Int |
| |
| Pointers and Buffers Modified: |
| lpc_coef = used to return the calculated LPC coefs in-place. |
| Int * |
| |
| Global Stores Modified: |
| None |
| |
| ------------------------------------------------------------------------------ |
| FUNCTION DESCRIPTION |
| |
| This function calculates the LPC coefs from the encoded coefs... |
| |
| ------------------------------------------------------------------------------ |
| REQUIREMENTS |
| |
| This function should match the functionality of the ISO source code within |
| a reasonable tolerance for fixed point errors. |
| |
| ------------------------------------------------------------------------------ |
| REFERENCES |
| |
| (1) ISO/IEC 14496-3:1999(E) |
| Part 3 |
| Subpart 4.6.8 (Temporal Noise Shaping) |
| (2) Markel & Gray Page 95 |
| As referenced in the ISO source code |
| |
| (3) 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. |
| |
| ------------------------------------------------------------------------------ |
| */ |
| |
| /*---------------------------------------------------------------------------- |
| PSEUDOCODE: (ISO Reference Code) |
| |
| int i, m; |
| Real iqfac, iqfac_m; |
| Real lpc_fp[TNS_MAX_ORDER+1]; |
| Real sin_result_fp[TNS_MAX_ORDER+1], b[TNS_MAX_ORDER+1]; |
| |
| Inverse quantization |
| iqfac = (Real)(((1 << (coef_res-1)) - 0.5) / (PI/2.0)); |
| iqfac_m = (Real)(((1 << (coef_res-1)) + 0.5) / (PI/2.0)); |
| |
| for (i=0; i<order; i++) |
| { |
| sin_result[i+1] = |
| (Real)sin( coef[i] / ((coef[i] >= 0) ? iqfac : iqfac_m) ); |
| } |
| |
| lpc[0] = 1; |
| for (m=1; m<=order; m++) |
| { |
| |
| b[0] = lpc[0]; |
| for (i=1; i<m; i++) |
| { |
| b[i] = sin_result[m] * lpc[m-i]; |
| b[i] += lpc[i]; |
| } |
| |
| b[m] = sin_result[m]; |
| |
| |
| for (i=0; i<=m; i++) |
| { |
| lpc[i] = b[i]; |
| } |
| |
| } |
| |
| return; |
| |
| } |
| ----------------------------------------------------------------------------*/ |
| |
| /*---------------------------------------------------------------------------- |
| ; INCLUDES |
| ----------------------------------------------------------------------------*/ |
| #include "pv_audio_type_defs.h" |
| #include "e_tns_const.h" |
| #include "tns_decode_coef.h" |
| #include "fxp_mul32.h" |
| |
| /*---------------------------------------------------------------------------- |
| ; MACROS |
| ; Define module specific macros here |
| ----------------------------------------------------------------------------*/ |
| |
| /*---------------------------------------------------------------------------- |
| ; DEFINES |
| ; Include all pre-processor statements here. Include conditional |
| ; compile variables also. |
| ----------------------------------------------------------------------------*/ |
| #define MASK_LOW16 0xffff |
| #define UPPER16 16 |
| |
| /*---------------------------------------------------------------------------- |
| ; LOCAL FUNCTION DEFINITIONS |
| ; Function Prototype declaration |
| ----------------------------------------------------------------------------*/ |
| |
| /*---------------------------------------------------------------------------- |
| ; LOCAL VARIABLE DEFINITIONS |
| ; Variable declaration - defined here and used outside this module |
| ----------------------------------------------------------------------------*/ |
| /* |
| * Derivation of tns_tables and q_tns_tables |
| * |
| * As defined in the ISO source code |
| * (with the modification that our coef_res has a range[0,1] |
| * The ISO code has a range of [3,4]) |
| * |
| * pi / 2 pi / 2 |
| * iqfac = -------------------- iqfac_m = -------------------- |
| * (coef_res + 2) - 1/ (coef_res + 2) + 1/ |
| * 2 /2 2 /2 |
| * |
| * |
| * ... Move 1/2 into denominator |
| * |
| * pi pi |
| * iqfac = -------------------- iqfac_m = -------------------- |
| * (coef_res + 3) (coef_res + 3) |
| * 2 - 1 2 + 1 |
| * |
| * |
| * if a coef is negative, it is multiplied by iqfac_m |
| * if positive, " " " iqfac |
| * |
| * The range of coefs is limited to -4:3 if coef_res = 0 |
| * -8:7 if coef_res = 1 |
| * |
| * |
| * |
| */ |
| |
| |
| const Int32 tns_table[2][16] = |
| { |
| { |
| -2114858546, -1859775393, -1380375881, -734482665, |
| 0, 931758235, 1678970324, 2093641749 |
| }, |
| { |
| -2138322861, -2065504841, -1922348530, -1713728946, |
| -1446750378, -1130504462, -775760571, -394599085, |
| 0, 446486956, 873460290, 1262259218, |
| 1595891361, 1859775393, 2042378317, 2135719508 |
| } |
| }; |
| |
| |
| const Int neg_offset[2] = {4, 8}; |
| /*---------------------------------------------------------------------------- |
| ; EXTERNAL FUNCTION REFERENCES |
| ; Declare functions defined elsewhere and referenced in this module |
| ----------------------------------------------------------------------------*/ |
| |
| /*---------------------------------------------------------------------------- |
| ; EXTERNAL VARIABLES REFERENCES |
| ; Declare variables used in this module but defined elsewhere |
| ----------------------------------------------------------------------------*/ |
| |
| /*---------------------------------------------------------------------------- |
| FUNCTION NAME: tns_decode_coef |
| Decoder transmitted coefficients for one TNS filter |
| ----------------------------------------------------------------------------*/ |
| |
| Int tns_decode_coef( |
| const Int order, |
| const Int coef_res, |
| Int32 lpc_coef[TNS_MAX_ORDER], |
| Int32 scratchTnsDecCoefMem[2*TNS_MAX_ORDER]) |
| { |
| |
| /* Simple loop counters */ |
| Int i; |
| Int m; |
| |
| /* Arrays for calculation of the LPC */ |
| Int32 *pB = &(scratchTnsDecCoefMem[TNS_MAX_ORDER]); |
| |
| Int32 *pA = scratchTnsDecCoefMem; |
| |
| Int32 *temp_ptr = NULL; |
| |
| /* Pointer for reading/storing the lpc_coef in place */ |
| Int32 *pLPC; |
| Int q_lpc = Q_LPC; |
| |
| /* TNS table related variables */ |
| const Int32 *pTnsTable; |
| Int coef_offset; |
| Int32 table_index; |
| Int shift_amount; |
| Int32 sin_result; |
| |
| Int32 tempInt32; |
| |
| Int32 max; |
| Int32 mask; |
| |
| Int32 mult_high; |
| |
| /* Conversion to LPC coefficients Ref. (2) */ |
| coef_offset = neg_offset[coef_res]; |
| pTnsTable = tns_table[coef_res]; |
| |
| m = 0; |
| pLPC = lpc_coef; |
| |
| |
| /* |
| * Conversion to LPC coefficients |
| */ |
| |
| do |
| { |
| table_index = coef_offset + *(pLPC++); |
| |
| /* Equiv. to sin_result = tns_table[coef_res][table_index]; */ |
| sin_result = *(pTnsTable + table_index); |
| |
| /* sin_result has a range of -0.999 to +0.999 in Q-31 */ |
| |
| /* |
| * It is important that this for loop is not entered on the first |
| * iteration of the do-while( m < order ) loop. |
| */ |
| for (i = m; i > 0; i--) |
| { |
| |
| /* |
| * temp_ptr used to optimize index into pA |
| * mult = (Int32)( pA[m-i] * sin_result); |
| */ |
| |
| mult_high = fxp_mul32_Q31(*(temp_ptr--), sin_result); |
| |
| /* |
| * pB[i] = pA[i] + sin_result * pA[m-i] |
| * |
| * (mult_high <<1) eliminates extra sign bit |
| */ |
| |
| *(pB++) = *(pA++) + (mult_high << 1); |
| |
| } /* END for (i=m; i > 0; i--) */ |
| |
| |
| /* Shift to place pB[m] in q_lpc format */ |
| |
| *pB = sin_result >> 12; |
| |
| /* |
| * Swapping the pointers here has the same effect |
| * as specifically copying the data from b to a |
| */ |
| |
| temp_ptr = pA; |
| pA = pB; |
| pB = temp_ptr; |
| |
| /* |
| * At this point, pA = pA[m] |
| * and pB = pB[m] |
| */ |
| temp_ptr = pA; |
| |
| tempInt32 = *(pA); |
| |
| mask = tempInt32 >> 31; |
| tempInt32 ^= mask; |
| |
| max = tempInt32; |
| |
| /* |
| * It is important that this for loop is not entered on the first |
| * iteration of the do-while( m < order ) loop. |
| */ |
| for (i = m; i > 0; i--) |
| { |
| tempInt32 = *(--pA); |
| |
| mask = tempInt32 >> 31; |
| tempInt32 ^= mask; |
| |
| max |= tempInt32; |
| } |
| |
| pB -= m; |
| |
| /* |
| * Here, pA = &(pA[0]) |
| * and pB = &(pB[0]) |
| */ |
| |
| if (max >= 0x40000000L) |
| { |
| max >>= 1; |
| |
| for (i = m; i > 0; i--) |
| { |
| *(pA++) >>= 1; |
| *(pB++) >>= 1; |
| } |
| |
| /* Shift the most recent entry down also */ |
| *(pA) >>= 1; |
| |
| q_lpc--; |
| |
| pA -= m; |
| pB -= m; |
| } |
| |
| m++; |
| |
| } |
| while (m < order); |
| |
| |
| /* |
| * The following code compacts |
| * 32-bit LPC coefficients into 16-bit numbers, |
| * shifting by the minimum amount necessary. |
| */ |
| |
| shift_amount = 0; |
| |
| while (max > 32767) |
| { |
| max >>= 1; |
| shift_amount++; |
| } |
| |
| /* |
| * This while loop is for protective purposes only. |
| * I have not found data that causes it to be entered. |
| * |
| */ |
| if (max != 0) |
| { |
| while (max < 16384) |
| { |
| max <<= 1; |
| shift_amount--; |
| } |
| } |
| |
| |
| pLPC = lpc_coef; |
| |
| if (shift_amount >= 0) |
| { |
| |
| for (m = order; m > 0; m--) |
| { |
| *(pLPC++) = *(pA++) << (16 - shift_amount); |
| } |
| } |
| |
| |
| q_lpc -= shift_amount; |
| |
| /* |
| * make sure that the numbers have some meaning, q_lpc can not be |
| * bigger than 15 (15 bits + sign) |
| */ |
| |
| if (q_lpc > 15) |
| { |
| shift_amount = q_lpc - 15; |
| pLPC = lpc_coef; |
| |
| for (m = order; m > 0; m--) |
| { |
| *(pLPC++) >>= shift_amount; |
| } |
| |
| q_lpc -= shift_amount; |
| } |
| |
| return (q_lpc); |
| |
| } /* tns_decode_coef */ |
