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Diffstat (limited to 'media/libstagefright/codecs/aacdec/tns_inv_filter.cpp')
| -rw-r--r-- | media/libstagefright/codecs/aacdec/tns_inv_filter.cpp | 421 |
1 files changed, 421 insertions, 0 deletions
diff --git a/media/libstagefright/codecs/aacdec/tns_inv_filter.cpp b/media/libstagefright/codecs/aacdec/tns_inv_filter.cpp new file mode 100644 index 0000000..631f887 --- /dev/null +++ b/media/libstagefright/codecs/aacdec/tns_inv_filter.cpp @@ -0,0 +1,421 @@ +/* ------------------------------------------------------------------ + * 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_inv_filter.c + +------------------------------------------------------------------------------ + REVISION HISTORY + + Description: Changes made per review comments. + + Description: As requested by JT, the q-format for the LPC coefficients is + now passed via the parameter lpc_qformat. + + Description: For speed, the calculation of the shift amount was pulled + outside of the loop. + + Description: + Modified casting to ensure proper operations for different platforms + + Description: + Simplified MAC operations for filter by eliminating extra variables + + Who: Date: + Description: + +------------------------------------------------------------------------------ + INPUT AND OUTPUT DEFINITIONS + + Inputs: + + coef = spectral input to be shaped by the filter. + Fixed point format + [Int32[], length = num_coef] + + num_coef = length of spec array. + [const Int] + + direction = direction for application of tns filter. + +1 applies forward filter + (first input to filter is coef[0]) + -1 applies reversed filter + (first input to filter is coef[num_coef-1]) + [const Int] + + lpc = array of lpc coefficients. + Fixed point format Q-11 + [const Int[], length = TNS_MAX_ORDER] + + lpc_qformat = The q-format of the lpc coefficients. + [const Int] + + order = order of the TNS filter (Range of 1 : TNS_MAX_ORDER) + [const Int] + + scratch_memory = scratch_memory needed for filter operation + [Int[], length = TNS_MAX_ORDER] + + Local Stores/Buffers/Pointers Needed: + None + + Global Stores/Buffers/Pointers Needed: + None + + Outputs: + None + + Pointers and Buffers Modified: + coef = contains spectral data after application of TNS filter + q-format is not modified. + Int32 array + length = num_coef + + Local Stores Modified: + None + + Global Stores Modified: + None + +------------------------------------------------------------------------------ + FUNCTION DESCRIPTION + + A block of spectral data (Int32 coef[]) of length (const Int num_coef) + is processed by a simple all-zero filter defined by + LPC coefficients passed via (const Int lpc[]) + + TNS filter equation + y(n) = x(n) + lpc(2)*x(n-1) + ... + lpc(order+1)*x(n-order) + + The filter calculation is performed in place, i.e. the output is passed + back to the calling function via (Int32 coef[]) + + In order to avoid overflow, the filter input (Int32 coef[]) must utilize + only the lower 16-bits. The upper 16-bits must be available. + + The filter's order is defined by the variable (const Int order) + + The direction of the filter's application is defined by + (const Int direction) + +------------------------------------------------------------------------------ + REQUIREMENTS + + [Int32 coef] must store no more than 16 bits of data. + + This is required to utilize methods that do not change the q-format of + the input data [Int32 coef], and to make use of a fast + 16 x 16 bit multiply. + + This function should not be called for order <= 0. + + This function must not be called with lpc_qformat < 5 +------------------------------------------------------------------------------ + REFERENCES + + (1) ISO/IEC 14496-3:1999(E) + Part 3 + Subpart 4.6.6.4.1 (LTP with TNS) + Subpart 4.6.8 (Temporal Noise Shaping) + + (2) 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. + +------------------------------------------------------------------------------ + PSEUDO-CODE + + IF (direction == -1) + THEN + pCoef = pCoef + (num_coef - 1); + END IF + + FOR (i = order; i > 0; i--) + + *(pFilterInput) = 0; + pFilterInput = pFilterInput + 1; + + END FOR + + wrap_point = 0; + + shift_amt = (lpc_qformat - 5); + + FOR (i = num_coef; i > 0; i--) + + pLPC = lpc; + + mult = 0; + + FOR (j = wrap_point; j>0; j--) + + tempInt32 = (Int32)(*(pLPC) * *(pFilterInput)); + tempInt32 = tempInt32 >> 5; + + mult = mult + tempInt32; + + pFilterInput = pFilterInput + 1; + pLPC = pLPC + 1; + + ENDFOR + + pFilterInput = scratch_memory; + + FOR (j = (order - wrap_point); j>0; j--) + + tempInt32 = (Int32)(*(pLPC) * *(pFilterInput)); + tempInt32 = tempInt32 >> 5; + + mult = mult + tempInt32; + + pFilterInput = pFilterInput + 1; + pLPC = pLPC + 1; + + ENDFOR + + pFilterInput = pFilterInput - 1; + *(pFilterInput) = (Int)(*pCoef); + + mult = mult >> shift_amt; + + *(pCoef) = *(pCoef) + mult; + + pCoef = pCoef + direction; + + wrap_point = wrap_point + 1; + + IF (wrap_point == order) + THEN + wrap_point = 0; + END IF + + END FOR + +------------------------------------------------------------------------------ + RESOURCES USED + + When the code is written for a specific target processor + 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 "tns_inv_filter.h" +#include "fxp_mul32.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 tns_inv_filter( + Int32 coef[], + const Int num_coef, + const Int direction, + const Int32 lpc[], + const Int lpc_qformat, + const Int order, + Int32 scratch_memory[]) +{ + + Int i; + Int j; + Int shift_amt; + Int wrap_point; + + Int32 mult; + + /* + * Circular buffer to hold the filter's input + * + * (x[n-1],x[n-2],x[n-3],etc.) + * + * This scratch space is necessary, because + * the filter's output is returned in-place. + * + * pFilterInput and pLPC should take advantage + * of any special circular buffer instructions + * if this code is hand-optimized in assembly. + * + */ + Int32 *pFilterInput = scratch_memory; + + const Int32 *pLPC; + + /* + * Pointer to the I/O memory space + */ + Int32 *pCoef = coef; + + if (direction == -1) + { + pCoef += (num_coef - 1); + } + + /* Make sure the scratch memory is "clean" */ + for (i = order; i != 0; i--) + { + *(pFilterInput++) = 0; + } + + wrap_point = 0; + + shift_amt = (lpc_qformat - 5); + + for (i = num_coef; i > 0; i--) + { + /* + * Copy spectral input into special + * filter input buffer. + */ + pLPC = lpc; + + mult = 0; + + /* + * wrap_point = 0 when this code is + * entered for the first iteration of + * for(i=num_coef; i>0; i--) + * + * So, this first for-loop will be + * skipped when i == num_coef. + */ + + for (j = wrap_point; j > 0; j--) + { + mult += fxp_mul32_Q31(*(pLPC++), *(pFilterInput++)) >> 5; + + } /* for (j = wrap_point; j>0; j--) */ + + /* + * pFilterInput has reached &scratch_memory[order-1] + * Reset pointer to beginning of filter's state memory + */ + pFilterInput = scratch_memory; + + for (j = (order - wrap_point); j > 0; j--) + { + mult += fxp_mul32_Q31(*(pLPC++), *(pFilterInput++)) >> 5; + + } /* for (j = wrap_point; j>0; j--) */ + + + /* + * Fill the filter's state buffer + * avoid obvious casting + */ + *(--pFilterInput) = (*pCoef); + + + /* Scale the data down so the output q-format is not adjusted. + * + * Here is an equation, which shows how the spectral coefficients + * and lpc coefficients are multiplied and the spectral + * coefficient's q-format does not change. + * + * Q-(coef) * Q-(lpc_qformat) >> 5 = Q-(coef + lpc_q_format - 5) + * + * Q-(coef + lpc_q_format - 5) >> (lpc_qformat - 5) = Q-(coef) + */ + + /* Store output in place */ + *(pCoef) += (mult >> shift_amt); + + /* Adjust pointers and placeholders */ + pCoef += direction; + + wrap_point++; + + if (wrap_point == order) + { + wrap_point = 0; + } + + } /* for (i = num_coef; i > 0; i--) */ + +} /* tns_inv_filter */ |