1 /*****************************************************************************
2 * layer1.c: MPEG Layer I audio decoder
3 *****************************************************************************
4 * Copyright (C) 1999-2001 VideoLAN
5 * $Id: layer1.c,v 1.2 2002/08/08 00:35:11 sam Exp $
7 * Authors: Michel Kaempf <maxx@via.ecp.fr>
8 * Michel Lespinasse <walken@via.ecp.fr>
10 * This program is free software; you can redistribute it and/or modify
11 * it under the terms of the GNU General Public License as published by
12 * the Free Software Foundation; either version 2 of the License, or
13 * (at your option) any later version.
15 * This program is distributed in the hope that it will be useful,
16 * but WITHOUT ANY WARRANTY; without even the implied warranty of
17 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
18 * GNU General Public License for more details.
20 * You should have received a copy of the GNU General Public License
21 * along with this program; if not, write to the Free Software
22 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111, USA.
23 *****************************************************************************/
25 #include <stdlib.h> /* NULL */
26 #include <string.h> /* memcpy(), memset() */
29 #include <vlc/decoder.h>
33 #include "math.h" /* DCT32(), PCM() */
37 static float adec_scalefactor_table[64] =
39 2.0000000000000000, 1.5874010519681994, 1.2599210498948732,
40 1.0000000000000000, 0.7937005259840998, 0.6299605249474366,
41 0.5000000000000000, 0.3968502629920499, 0.3149802624737183,
42 0.2500000000000000, 0.1984251314960249, 0.1574901312368591,
43 0.1250000000000000, 0.0992125657480125, 0.0787450656184296,
44 0.0625000000000000, 0.0496062828740062, 0.0393725328092148,
45 0.0312500000000000, 0.0248031414370031, 0.0196862664046074,
46 0.0156250000000000, 0.0124015707185016, 0.0098431332023037,
47 0.0078125000000000, 0.0062007853592508, 0.0049215666011518,
48 0.0039062500000000, 0.0031003926796254, 0.0024607833005759,
49 0.0019531250000000, 0.0015501963398127, 0.0012303916502880,
50 0.0009765625000000, 0.0007750981699063, 0.0006151958251440,
51 0.0004882812500000, 0.0003875490849532, 0.0003075979125720,
52 0.0002441406250000, 0.0001937745424766, 0.0001537989562860,
53 0.0001220703125000, 0.0000968872712383, 0.0000768994781430,
54 0.0000610351562500, 0.0000484436356191, 0.0000384497390715,
55 0.0000305175781250, 0.0000242218178096, 0.0000192248695357,
56 0.0000152587890625, 0.0000121109089048, 0.0000096124347679,
57 0.0000076293945312, 0.0000060554544524, 0.0000048062173839,
58 0.0000038146972656, 0.0000030277272262, 0.0000024031086920,
59 0.0000019073486328, 0.0000015138636131, 0.0000012015543460,
60 0.0000009536743164 /* last element is not in the standard... invalid ??? */
63 static float adec_slope_table[15] =
65 0.6666666666666666, 0.2857142857142857, 0.1333333333333333,
66 0.0645161290322581, 0.0317460317460317, 0.0157480314960630,
67 0.0078431372549020, 0.0039138943248532, 0.0019550342130987,
68 0.0009770395701026, 0.0004884004884005, 0.0002441704309608,
69 0.0001220777635354, 0.0000610370189520, 0.0000305180437934
72 static float adec_offset_table[15] =
74 -0.6666666666666666, -0.8571428571428571, -0.9333333333333333,
75 -0.9677419354838710, -0.9841269841269841, -0.9921259842519685,
76 -0.9960784313725490, -0.9980430528375733, -0.9990224828934506,
77 -0.9995114802149487, -0.9997557997557998, -0.9998779147845196,
78 -0.9999389611182323, -0.9999694814905240, -0.9999847409781033
81 static u8 adec_layer1_allocation_table[15] =
83 0, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15
86 static int adec_bound_table[4] = { 4, 8, 12, 16 };
88 int adec_layer1_mono( adec_thread_t * p_adec, s16 * buffer )
95 unsigned int i_sb, s, i_read_bits = 0;
98 * Parse the allocation tables
101 for (i_sb = 0; i_sb < 32; i_sb += 2)
105 /* i_read_bits will be updated at the end of the loop */
106 tmp = GetBits ( &p_adec->bit_stream, 8 );
108 if ( (tmp >> 4) > 14 )
113 allocation[i_sb] = adec_layer1_allocation_table [tmp >> 4];
120 allocation[i_sb+1] = adec_layer1_allocation_table [tmp & 15];
123 i_read_bits += 8 * 16; /* we did 16 iterations */
129 for ( i_sb = 0; i_sb < 32; i_sb++ )
131 if ( allocation[i_sb] )
136 index = GetBits( &p_adec->bit_stream, 6);
138 /* We also add the bits we'll take later in the sample parsing */
139 i_read_bits += 6 + 12 * allocation[i_sb];
141 scalefactor = adec_scalefactor_table[index];
143 slope[i_sb] = adec_slope_table[allocation[i_sb]-2] * scalefactor;
144 offset[i_sb] = adec_offset_table[allocation[i_sb]-2] * scalefactor;
152 for ( s = 0 ; s < 12; s++)
154 for (i_sb = 0; i_sb < 32; i_sb++)
156 if (!allocation[i_sb])
164 /* The bits were already counted in the scalefactors parsing */
165 code = GetBits( &p_adec->bit_stream, allocation[i_sb] );
167 sample[i_sb] = slope[i_sb] * code + offset[i_sb];
171 DCT32( &p_adec->bank_0, sample );
172 PCM (&p_adec->bank_0, buffer, 1);
176 p_adec->i_read_bits += i_read_bits;
181 int adec_layer1_stereo( adec_thread_t * p_adec, s16 * buffer )
183 u8 allocation_0[32], allocation_1[32];
184 float slope_0[32], slope_1[32];
185 float offset_0[32], offset_1[32];
186 float sample_0[32], sample_1[32];
198 if ( (p_adec->header & 0xc0) == 0x40)
200 /* intensity stereo */
202 index = (p_adec->header >> 4) & 3;
203 bound = adec_bound_table[index];
210 for (i_sb = 0; i_sb < bound; i_sb++)
213 tmp = GetBits( &p_adec->bit_stream, 8 );
218 allocation_0[i_sb] = adec_layer1_allocation_table [tmp >> 4];
223 allocation_1[i_sb] = adec_layer1_allocation_table [tmp & 15];
226 for (; i_sb < 32; i_sb += 2)
229 tmp = GetBits( &p_adec->bit_stream, 8 );
235 allocation_0[i_sb] = allocation_1[i_sb]
236 = adec_layer1_allocation_table [tmp >> 4];
242 allocation_0[i_sb+1] = allocation_1[i_sb+1]
243 = adec_layer1_allocation_table [tmp & 15];
246 i_read_bits += 4 * ( 32 + bound ); /* we read 8*bound and 4*(32-bound) */
252 for ( i_sb = 0; i_sb < 32; i_sb++ )
254 if ( allocation_0[i_sb] )
259 index = GetBits( &p_adec->bit_stream, 6 );
262 scalefactor = adec_scalefactor_table[index];
264 slope_0[i_sb] = adec_slope_table[allocation_0[i_sb]-2] * scalefactor;
265 offset_0[i_sb] = adec_offset_table[allocation_0[i_sb]-2] * scalefactor;
268 if (allocation_1[i_sb])
273 index = GetBits( &p_adec->bit_stream, 6 );
276 scalefactor = adec_scalefactor_table[index];
278 slope_1[i_sb] = adec_slope_table[allocation_1[i_sb]-2] * scalefactor;
279 offset_1[i_sb] = adec_offset_table[allocation_1[i_sb]-2] * scalefactor;
285 for (s = 0; s < 12; s++)
287 for (i_sb = 0; i_sb < bound; i_sb++)
289 if (!allocation_0[i_sb])
297 code = GetBits( &p_adec->bit_stream, allocation_0[i_sb] );
298 i_read_bits += allocation_0[i_sb];
300 sample_0[i_sb] = slope_0[i_sb] * code + offset_0[i_sb];
303 if ( !allocation_1[i_sb] )
311 code = GetBits( &p_adec->bit_stream, allocation_1[i_sb] );
312 i_read_bits += allocation_1[i_sb];
314 sample_1[i_sb] = slope_1[i_sb] * code + offset_1[i_sb];
318 for (; i_sb < 32; i_sb++)
320 if (!allocation_0[i_sb])
329 code = GetBits( &p_adec->bit_stream, allocation_0[i_sb] );
330 i_read_bits += allocation_0[i_sb];
332 sample_0[i_sb] = slope_0[i_sb] * code + offset_0[i_sb];
333 sample_1[i_sb] = slope_1[i_sb] * code + offset_1[i_sb];
337 DCT32( &p_adec->bank_0, sample_0 );
338 PCM (&p_adec->bank_0, buffer, 2);
339 DCT32( &p_adec->bank_1, sample_1 );
340 PCM (&p_adec->bank_1, buffer + 1, 2);
344 p_adec->i_read_bits += i_read_bits;