| /* ------------------------------------------------------------------ |
| * 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. |
| * ------------------------------------------------------------------- |
| */ |
| /* |
| ------------------------------------------------------------------------------ |
| |
| PacketVideo Corp. |
| MP3 Decoder Library |
| |
| Filename: pvmp3_alias_reduction.cpp |
| |
| Date: 09/21/2007 |
| |
| ------------------------------------------------------------------------------ |
| REVISION HISTORY |
| |
| |
| Description: |
| |
| ------------------------------------------------------------------------------ |
| INPUT AND OUTPUT DEFINITIONS |
| |
| Input |
| int32 *input_buffer, Ptr to fequency lines of current channel |
| struct gr_info_s *gr_info, structure with granuke information for the |
| input |
| mp3Header *info mp3 header information |
| |
| ------------------------------------------------------------------------------ |
| FUNCTION DESCRIPTION |
| |
| Alias Reduction |
| |
| |
| |
| Alias reduction before processing by the IMDCT |
| |
| Csi + |
| >---------0---------0--------> |
| \ / - |
| Cai \ / |
| \ / |
| \ / |
| \ |
| / \ |
| Cai / \ |
| / \ + |
| >--------0---------0----------> |
| Csi + |
| |
| Aliasing Butterfly |
| Alias reduction is not applied to short blocks |
| |
| ------------------------------------------------------------------------------ |
| REQUIREMENTS |
| |
| |
| ------------------------------------------------------------------------------ |
| REFERENCES |
| |
| [1] ISO MPEG Audio Subgroup Software Simulation Group (1996) |
| ISO 13818-3 MPEG-2 Audio Decoder - Lower Sampling Frequency Extension |
| |
| ------------------------------------------------------------------------------ |
| PSEUDO-CODE |
| 1 ci |
| csi = ---------------- csi = ---------------- |
| sqrt( 1 + (ci^2)) sqrt( 1 + (ci^2)) |
| |
| |
| ci = -0.6, -0.535, -0.33, -0.185, -0.095, -0.041, -0.0142, -0.0037 |
| |
| ------------------------------------------------------------------------------ |
| */ |
| |
| |
| /*---------------------------------------------------------------------------- |
| ; INCLUDES |
| ----------------------------------------------------------------------------*/ |
| |
| #include "pvmp3_alias_reduction.h" |
| #include "pv_mp3dec_fxd_op.h" |
| |
| |
| /*---------------------------------------------------------------------------- |
| ; MACROS |
| ; Define module specific macros here |
| ----------------------------------------------------------------------------*/ |
| |
| |
| /*---------------------------------------------------------------------------- |
| ; DEFINES |
| ; Include all pre-processor statements here. Include conditional |
| ; compile variables also. |
| ----------------------------------------------------------------------------*/ |
| #define NUM_BUTTERFLIES 8 |
| |
| #define Q31_fmt(a) (int32(double(0x7FFFFFFF)*(a))) |
| |
| /*---------------------------------------------------------------------------- |
| ; LOCAL FUNCTION DEFINITIONS |
| ; Function Prototype declaration |
| ----------------------------------------------------------------------------*/ |
| |
| /*---------------------------------------------------------------------------- |
| ; LOCAL STORE/BUFFER/POINTER DEFINITIONS |
| ; Variable declaration - defined here and used outside this module |
| ----------------------------------------------------------------------------*/ |
| const int32 c_signal [ NUM_BUTTERFLIES ] = |
| { |
| |
| Q31_fmt(0.85749292571254f), Q31_fmt(0.88174199731771f), |
| Q31_fmt(0.94962864910273f), Q31_fmt(0.98331459249179f), |
| Q31_fmt(0.99551781606759f), Q31_fmt(0.99916055817815f), |
| Q31_fmt(0.99989919524445f), Q31_fmt(0.99999315507028f) |
| |
| }; |
| |
| |
| const int32 c_alias [ NUM_BUTTERFLIES ] = |
| { |
| |
| Q31_fmt(-0.51449575542753f), Q31_fmt(-0.47173196856497f), |
| Q31_fmt(-0.31337745420390f), Q31_fmt(-0.18191319961098f), |
| Q31_fmt(-0.09457419252642f), Q31_fmt(-0.04096558288530f), |
| Q31_fmt(-0.01419856857247f), Q31_fmt(-0.00369997467376f) |
| }; |
| |
| /*---------------------------------------------------------------------------- |
| ; 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 pvmp3_alias_reduction(int32 *input_buffer, /* Ptr to spec values of current channel */ |
| granuleInfo *gr_info, |
| int32 *used_freq_lines, |
| mp3Header *info) |
| { |
| int32 *ptr1; |
| int32 *ptr2; |
| int32 *ptr3; |
| int32 *ptr4; |
| const int32 *ptr_csi; |
| const int32 *ptr_csa; |
| int32 sblim; |
| |
| int32 i, j; |
| |
| *used_freq_lines = fxp_mul32_Q32(*used_freq_lines << 16, (int32)((float)0x7FFFFFFF / 18.0f - 1.0f)) >> 15; |
| |
| |
| if (gr_info->window_switching_flag && gr_info->block_type == 2) |
| { |
| if (gr_info->mixed_block_flag) |
| { |
| sblim = ((info->version_x == MPEG_2_5) && (info->sampling_frequency == 2)) ? 3 : 1; |
| } |
| else |
| { |
| return; /* illegal parameter */ |
| } |
| } |
| else |
| { |
| sblim = *used_freq_lines + 1; |
| |
| if (sblim > SUBBANDS_NUMBER - 1) |
| { |
| sblim = SUBBANDS_NUMBER - 1; /* default */ |
| } |
| |
| } |
| |
| |
| ptr3 = &input_buffer[17]; |
| ptr4 = &input_buffer[18]; |
| ptr_csi = c_signal; |
| ptr_csa = c_alias; |
| |
| /* NUM_BUTTERFLIES (=8) butterflies between each pair of sub-bands*/ |
| |
| for (i = NUM_BUTTERFLIES >> 1; i != 0; i--) |
| { |
| int32 csi1 = *ptr_csi++; |
| int32 csi2 = *ptr_csi++; |
| int32 csa1 = *ptr_csa++; |
| int32 csa2 = *ptr_csa++; |
| |
| ptr1 = ptr3; |
| ptr3 -= 2; |
| ptr2 = ptr4; |
| ptr4 += 2; |
| |
| /* |
| * "sblim" alias-reduction operations between each |
| * pair of sub-bands |
| */ |
| |
| for (j = sblim >> 1; j != 0; j--) |
| { |
| int32 y = *ptr2; |
| int32 x = *ptr1 << 1; |
| *ptr1-- = fxp_msb32_Q32(fxp_mul32_Q32(x, csi1), y << 1, csa1); |
| *ptr2++ = fxp_mac32_Q32(fxp_mul32_Q32(y << 1, csi1), x, csa1); |
| y = *ptr2; |
| x = *ptr1 << 1; |
| *ptr1 = fxp_msb32_Q32(fxp_mul32_Q32(x, csi2), y << 1, csa2); |
| *ptr2 = fxp_mac32_Q32(fxp_mul32_Q32(y << 1, csi2), x, csa2); |
| ptr1 += 19; |
| ptr2 += 17; |
| y = *ptr2; |
| x = *ptr1 << 1; |
| *ptr1-- = fxp_msb32_Q32(fxp_mul32_Q32(x, csi1), y << 1, csa1); |
| *ptr2++ = fxp_mac32_Q32(fxp_mul32_Q32(y << 1, csi1), x, csa1); |
| y = *ptr2; |
| x = *ptr1 << 1; |
| *ptr1 = fxp_msb32_Q32(fxp_mul32_Q32(x, csi2), y << 1, csa2); |
| *ptr2 = fxp_mac32_Q32(fxp_mul32_Q32(y << 1, csi2), x, csa2); |
| ptr1 += 19; |
| ptr2 += 17; |
| |
| } |
| |
| if (sblim & 1) |
| { |
| int32 x = *ptr1 << 1; |
| int32 y = *ptr2; |
| *ptr1-- = fxp_msb32_Q32(fxp_mul32_Q32(x, csi1), y << 1, csa1); |
| *ptr2++ = fxp_mac32_Q32(fxp_mul32_Q32(y << 1, csi1), x, csa1); |
| |
| x = *ptr1 << 1; |
| y = *ptr2; |
| *ptr1 = fxp_msb32_Q32(fxp_mul32_Q32(x, csi2), y << 1, csa2); |
| *ptr2 = fxp_mac32_Q32(fxp_mul32_Q32(y << 1, csi2), x, csa2); |
| } |
| } |
| |
| } |
