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+/* ------------------------------------------------------------------
+ * 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 */
generated by cgit v1.1 at 2024-05-30 06:05:48 +0000