mirror of
https://github.com/RetroDECK/Supermodel.git
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226 lines
5.5 KiB
C++
226 lines
5.5 KiB
C++
/**
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** Supermodel
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** A Sega Model 3 Arcade Emulator.
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** Copyright 2011 Bart Trzynadlowski, Nik Henson
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**
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** This file is part of Supermodel.
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**
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** Supermodel is free software: you can redistribute it and/or modify it under
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** the terms of the GNU General Public License as published by the Free
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** Software Foundation, either version 3 of the License, or (at your option)
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** any later version.
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**
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** Supermodel is distributed in the hope that it will be useful, but WITHOUT
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** ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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** FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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** more details.
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**
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** You should have received a copy of the GNU General Public License along
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** with Supermodel. If not, see <http://www.gnu.org/licenses/>.
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**/
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/*
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* layer3.cpp
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*
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* Amp library internal module.
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*/
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/* this file is a part of amp software, (C) tomislav uzelac 1996,1997
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*/
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/* layer3.c layer3 audio decoding
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*
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* Created by: tomislav uzelac Mar 1 97
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* Last modified by:
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*/
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#include "amp.h"
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#include "audio.h"
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#include "dump.h"
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#include "getbits.h"
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#include "getdata.h"
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#include "huffman.h"
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#include "misc2.h"
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#include "rtbuf.h"
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#include "transform.h"
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#define LAYER3
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#include "layer3.h"
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void requantize_downmix(int gr,struct SIDE_INFO *info,struct AUDIO_HEADER *header);
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/* this function decodes one layer3 audio frame, except for the header decoding
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* which is done in main() [audio.c]. returns 0 if everything is ok.
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*/
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int layer3_frame(struct AUDIO_HEADER *header,int cnt)
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{
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static struct SIDE_INFO info;
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int gr,ch,sb,i;
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int mean_frame_size,bitrate,fs,hsize,ssize;
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/* we need these later, hsize is the size of header+side_info
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*/
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if (header->ID)
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if (header->mode==3) {
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nch=1;
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hsize=21;
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} else {
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nch=2;
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hsize=36;
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}
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else
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if (header->mode==3) {
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nch=1;
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hsize=13;
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} else {
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nch=2;
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hsize=21;
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}
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/* crc increases hsize by 2
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*/
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if (header->protection_bit==0) hsize+=2;
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/* read layer3 specific side_info
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*/
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getinfo(header,&info);
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/* MPEG2 only has one granule
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*/
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bitrate=t_bitrate[header->ID][3-header->layer][header->bitrate_index];
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fs=t_sampling_frequency[header->ID][header->sampling_frequency];
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if (header->ID) mean_frame_size=144000*bitrate/fs;
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else mean_frame_size=72000*bitrate/fs;
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/* check if mdb is too big for the first few frames. this means that
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* a part of the stream could be missing. We must still fill the buffer
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*
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* don't forget to (re)initialise bclean_bytes to 0, and f_bdirty to FALSE!!!
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*/
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if (f_bdirty)
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{
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if (info.main_data_begin > bclean_bytes) {
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fillbfr(mean_frame_size + header->padding_bit - hsize);
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bclean_bytes+=mean_frame_size + header->padding_bit - hsize;
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/* warn(" frame %d discarded, incomplete main_data\n",cnt); */
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return 0;
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} else {
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/* re-initialise */
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f_bdirty=FALSE;
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bclean_bytes=0;
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}
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}
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/* now update the data 'pointer' (counting in bits) according to
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* the main_data_begin information
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*/
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data = 8 * ((append - info.main_data_begin) & (BUFFER_SIZE-1));
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/* read into the buffer all bytes up to the start of next header
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*/
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fillbfr(mean_frame_size + header->padding_bit - hsize);
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/* these two should go away
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*/
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t_l=&t_b8_l[header->ID][header->sampling_frequency][0];
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t_s=&t_b8_s[header->ID][header->sampling_frequency][0];
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/* debug/dump stuff
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*/
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if (A_DUMP_BINARY) dump((int *)info.part2_3_length);
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/* decode the scalefactors and huffman data
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* this part needs to be enhanced for error robustness
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*/
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for (gr=0;gr < ((header->ID) ? 2 : 1);gr++) {
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for (ch=0;ch<nch;ch++) {
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ssize=decode_scalefactors(&info,header,gr,ch);
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decode_huffman_data(&info,gr,ch,ssize);
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}
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/* requantization, stereo processing, reordering(shortbl)
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*/
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if (A_DOWNMIX && nch==2) requantize_downmix(gr,&info,header);
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else
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if (header->mode!=1 || (header->mode==1 && header->mode_extension==0))
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for (ch=0;ch<nch;ch++) requantize_mono(gr,ch,&info,header);
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else requantize_ms(gr,&info,header);
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/* just which window?
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*/
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/* this is a very temporary, very ugly hack.
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*/
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if (A_DOWNMIX) nch=1;
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for (ch=0; ch < (A_DOWNMIX ? 1:nch) ;ch++) {
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int win_type; /* same as in the standard, long=0, start=1 ,.... */
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int window_switching_flag = info.window_switching_flag[gr][ch];
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int block_type = info.block_type[gr][ch];
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int mixed_block_flag = info.mixed_block_flag[gr][ch];
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/* antialiasing butterflies
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*/
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if (!(window_switching_flag &&
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block_type==2))
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alias_reduction(ch);
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if (window_switching_flag &&
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block_type==2 &&
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mixed_block_flag)
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win_type=0;
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else
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if (!window_switching_flag) win_type=0;
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else win_type=block_type;
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/* imdct ...
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*/
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for (sb=0;sb<2;sb++)
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imdct(win_type,sb,ch);
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if (window_switching_flag &&
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block_type==2 &&
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mixed_block_flag)
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win_type=2;
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/* no_of_imdcts tells us how many subbands from the top are all zero
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* it is set by the requantize functions in misc2.c
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*/
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for (sb=2;sb<no_of_imdcts[ch];sb++)
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imdct(win_type,sb,ch);
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for (;sb<32;sb++)
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for (i=0;i<18;i++) {
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res[sb][i]=s[ch][sb][i];
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s[ch][sb][i]=0.0f;
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}
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/* polyphase filterbank
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*/
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/* if (nch == 2) this was a bug, tomislav */
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for (i=0;i<18;i++)
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poly(ch,i);
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}
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printout();
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/* this is part2 of a particularily ugly hack. this should vanish as soon as nch isn't
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a global variable anymore
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*/
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if (A_DOWNMIX && header->mode!=3) nch=2;
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} /* for (gr... */
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/* return status: 0 for ok, errors will be added
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*/
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return 0;
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}
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