| /* ------------------------------------------------------------------ |
| * 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: pns_corr.c |
| |
| ------------------------------------------------------------------------------ |
| REVISION HISTORY |
| |
| Description: Made changes per review comments, the most major of which |
| being the change of the scaling into a 16 x 16 multiply. |
| |
| Description: When the multiplication of two 16-bits variables is stored in |
| an 32-bits variable, the result should be typecasted explicitly |
| to Int32 before it is stored. |
| *(pCoefRight++) = (Int32) tempInt2 * multiplier; |
| |
| Who: Date: |
| Description: |
| ------------------------------------------------------------------------------ |
| INPUT AND OUTPUT DEFINITIONS |
| |
| Inputs: |
| |
| scale = Multiplier used to scale the noise extracted from the left |
| channel for use on the right. |
| [const Int] |
| |
| coef_per_win = Number of coefficients per window. |
| (128 for short, 1024 for long) |
| [const Int] |
| |
| sfb_per_win = Number of scalefactors per window. |
| [const Int] |
| |
| wins_in_group = The number of windows in the group being decoded. |
| [const Int] |
| |
| band_length = The length of the scalefactor band being decoded. |
| [const Int] |
| |
| sfb_prediction_used = Flag that denotes the activation of long term |
| prediction on a per-scalefactor band, |
| non-grouped basis. |
| [const Int *, length MAX_SFB] |
| |
| q_formatLeft = The Q-format for the left channel's fixed-point spectral |
| coefficients, on a per-scalefactor band, non-grouped basis. |
| [const Int] |
| |
| q_formatRight = The Q-format for the right channel's fixed-point spectral |
| coefficients, on a per-scalefactor band, non-grouped basis. |
| [Int *, length MAX_SFB] |
| |
| coefLeft = Array containing the fixed-point spectral coefficients |
| for the left channel. |
| [const Int32 *, length 1024] |
| |
| coefRight = Array containing the fixed-point spectral coefficients |
| for the right channel. |
| [Int32 *, length 1024] |
| |
| Local Stores/Buffers/Pointers Needed: |
| |
| Global Stores/Buffers/Pointers Needed: |
| |
| Outputs: |
| |
| Pointers and Buffers Modified: |
| pcoefRight Contains the new spectral information |
| |
| q_formatRight Q-format may be updated with changed to fixed-point |
| data in coefRight. |
| |
| sfb_prediction_used LTP may be disabled by presence of PNS tool on the |
| same scalefactor band. |
| |
| Local Stores Modified: |
| |
| Global Stores Modified: |
| |
| ------------------------------------------------------------------------------ |
| FUNCTION DESCRIPTION |
| |
| This function derives noise from the left channel. The PNS tool is assumed |
| to have been used on the same scalefactor band on the left channel. The |
| noise on the left/right channels are not necessarily of the same amplitude, |
| and therefore have separate scalefactors. The noise is thus scaled by the |
| difference between the two transmitted scalefactors. This scaling is done |
| in fixed-point using a constant 4-element table. |
| |
| ------------------------------------------------------------------------------ |
| REQUIREMENTS |
| |
| |
| ------------------------------------------------------------------------------ |
| REFERENCES |
| |
| (1) ISO/IEC 14496-3:1999(E) |
| Part 3 |
| Subpart 4.6.7.1 M/S stereo |
| Subpart 4.6.12.3 Decoding Process (PNS) |
| Subpart 4.6.2 ScaleFactors |
| |
| (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 |
| |
| q_format = q_formatLeft - (scale >> 2); |
| q_format = q_format - 1; |
| q_formatRight = q_format; |
| |
| multiplier = hcb2_scale_mod_4[scale & 0x3]; |
| |
| pCoefLeft = coefLeft; |
| pCoefRight = coefRight; |
| |
| start_indx = 0; |
| |
| FOR (win_indx = wins_in_group; win_indx > 0; win_indx--) |
| |
| q_formatRight[start_indx] = q_format; |
| |
| sfb_prediction_used[start_indx] = FALSE; |
| |
| start_indx = start_indx + sfb_per_win; |
| |
| FOR (tempInt = band_length; tempInt > 0; tempInt--) |
| |
| *(pCoefRight) = (*(pCoefLeft) >> 9) * multiplier; |
| pCoefRight = pCoefRight + 1; |
| pCoefLeft = pCoefLeft + 1; |
| |
| ENDFOR |
| |
| tempInt = (coef_per_win - band_length); |
| pCoefRight = pCoefRight + tempInt; |
| pCoefLeft = pCoefLeft + tempInt; |
| |
| ENDFOR |
| |
| ------------------------------------------------------------------------------ |
| 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 "pns_corr.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 |
| ----------------------------------------------------------------------------*/ |
| |
| const UInt hcb2_scale_mod_4[4] = |
| { |
| 32768, /* (2.0^0.00)*2^15 */ |
| 38968, /* (2.0^0.25)*2^15 */ |
| 46341, /* (2.0^0.50)*2^15 */ |
| 55109 |
| }; /* (2.0^0.75)*2^15 */ |
| |
| /*---------------------------------------------------------------------------- |
| ; 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 pns_corr( |
| const Int scale, |
| const Int coef_per_win, |
| const Int sfb_per_win, |
| const Int wins_in_group, |
| const Int band_length, |
| const Int q_formatLeft, |
| Int q_formatRight[], |
| const Int32 coefLeft[], |
| Int32 coefRight[]) |
| { |
| Int tempInt; |
| Int nextWinPtrUpdate; |
| |
| Int q_format; |
| |
| Int start_indx; |
| Int win_indx; |
| |
| const Int32 *pCoefLeft; |
| Int32 *pCoefRight; |
| |
| UInt multiplier; |
| |
| /* |
| * Generate noise correlated with the noise on the left channel |
| * |
| */ |
| |
| /* |
| * scale is interpreted as 2^(scale/4) |
| * Therefore, we can adjust the q-format by floor(scale/4) |
| * and save some complexity in the multiplier. |
| */ |
| q_format = q_formatLeft - (scale >> 2); |
| |
| /* |
| * Reduce the q-format by 1 to guard against overflow. |
| * This must be done because the hcb2_scale_mod_4 table |
| * must be stored in a common q-format, and we must shift |
| * by 16 to get *pCoefLeft into a 16-bit value, but we |
| * cannot store 2^0*2^16 and 2^0.75*2^16 in a table. |
| */ |
| q_format--; |
| |
| multiplier = hcb2_scale_mod_4[scale & 0x3]; |
| |
| pCoefLeft = coefLeft; |
| pCoefRight = coefRight; |
| |
| nextWinPtrUpdate = (coef_per_win - band_length); |
| |
| /* |
| * Step through all the windows in this group, replacing this |
| * band in each window's spectrum with correlated random noise |
| */ |
| |
| start_indx = 0; |
| |
| for (win_indx = wins_in_group; win_indx > 0; win_indx--) |
| { |
| /* |
| * Set the q-format for all scalefactor bands in the group. |
| * Normally, we could not assume that grouped scalefactors |
| * share the same q-format. |
| * However, here we can make this assumption. The reason |
| * being -- if this function is called, it is assumed |
| * PNS was used on the left channel. When PNS is used, |
| * all scalefactors in a group share the same q-format. |
| * |
| */ |
| q_formatRight[start_indx] = q_format; |
| |
| start_indx += sfb_per_win; |
| |
| /* reconstruct right noise values */ |
| for (tempInt = band_length; tempInt > 0; tempInt--) |
| { |
| *(pCoefRight++) = (Int32)(*(pCoefLeft++) >> 16) * multiplier; |
| } |
| |
| pCoefRight += nextWinPtrUpdate; |
| pCoefLeft += nextWinPtrUpdate; |
| |
| } /* for (win_indx) */ |
| |
| return; |
| |
| } /* void pns_corr */ |
