1 /*****************************************************************************
2 * generic.c: MPEG audio decoder
3 *****************************************************************************
4 * Copyright (C) 1999-2001 VideoLAN
5 * $Id: generic.c,v 1.1 2002/08/04 17:23:42 sam Exp $
7 * Authors: Michel Kaempf <maxx@via.ecp.fr>
8 * Michel Lespinasse <walken@via.ecp.fr>
9 * Cyril Deguet <asmax@via.ecp.fr>
11 * This program is free software; you can redistribute it and/or modify
12 * it under the terms of the GNU General Public License as published by
13 * the Free Software Foundation; either version 2 of the License, or
14 * (at your option) any later version.
16 * This program is distributed in the hope that it will be useful,
17 * but WITHOUT ANY WARRANTY; without even the implied warranty of
18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19 * GNU General Public License for more details.
21 * You should have received a copy of the GNU General Public License
22 * along with this program; if not, write to the Free Software
23 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111, USA.
24 *****************************************************************************/
26 #include <string.h> /* memcpy(), memset() */
29 #include <vlc/decoder.h>
33 #include "math.h" /* DCT32(), PCM() */
37 int adec_Init( adec_thread_t * p_adec )
39 p_adec->bank_0.actual = p_adec->bank_0.v1;
40 p_adec->bank_0.pos = 0;
41 p_adec->bank_1.actual = p_adec->bank_1.v1;
42 p_adec->bank_1.pos = 0;
46 int adec_SyncFrame( adec_thread_t * p_adec, adec_sync_info_t * p_sync_info )
48 static int mpeg1_sample_rate[3] = {44100, 48000, 32000};
49 static int mpeg1_layer1_bit_rate[15] =
51 0, 32, 64, 96, 128, 160, 192, 224, 256, 288, 320, 352, 384, 416, 448
53 static int mpeg1_layer2_bit_rate[15] =
55 0, 32, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320, 384
57 static int mpeg2_layer1_bit_rate[15] =
59 0, 32, 48, 56, 64, 80, 96, 112, 128, 144, 160, 176, 192, 224, 256
61 static int mpeg2_layer2_bit_rate[15] =
63 0, 8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160
65 static int * bit_rate_table[8] =
67 NULL, NULL, mpeg2_layer2_bit_rate, mpeg2_layer1_bit_rate,
68 NULL, NULL, mpeg1_layer2_bit_rate, mpeg1_layer1_bit_rate
78 /* We read the whole header, but only really take 8 bits */
79 header = GetBits( &p_adec->bit_stream, 8 ) << 24;
80 header |= ShowBits( &p_adec->bit_stream, 24 );
82 p_adec->header = header;
84 /* basic header check : sync word */
85 if( (header & 0xfff00000) != 0xfff00000 )
90 /* calculate bit rate */
91 index = ( header >> 17 ) & 7; /* mpeg ID + layer */
92 bit_rates = bit_rate_table[ index ];
93 if( bit_rates == NULL )
95 return 1; /* invalid layer */
98 index = ( header >> 12 ) & 15; /* bit rate index */
103 bit_rate = bit_rates[ index ];
105 /* mpeg 1 layer 2 : check that bitrate per channel is valid */
107 if( bit_rates == mpeg1_layer2_bit_rate )
109 if( (header & 0xc0) == 0xc0 )
113 return 1; /* invalid bitrate per channel */
118 if( (1 << index) & 0x2e )
120 return 1; /* invalid bitrate per channel */
125 /* calculate sample rate */
127 index = ( header >> 10 ) & 3; /* sample rate index */
133 sample_rate = mpeg1_sample_rate[ index ];
135 if( ! (header & 0x80000) )
137 sample_rate >>= 1; /* half sample rate for mpeg2 */
140 /* calculate frame length */
142 if( (header & 0x60000) == 0x60000 )
145 frame_size = 48000 * bit_rate / sample_rate;
156 frame_size = 144000 * bit_rate / sample_rate;
165 /* Now we are sure we want this header, read it */
166 RemoveBits( &p_adec->bit_stream, 24 );
167 p_adec->i_read_bits = 32;
169 if( ! (p_adec->header & 0x10000) )
171 /* Error check, skip it */
172 RemoveBits( &p_adec->bit_stream, 16 );
173 p_adec->i_read_bits += 16;
176 p_sync_info->b_stereo = ((p_adec->header & 0xc0) != 0xc0);
177 p_sync_info->sample_rate = sample_rate;
178 p_sync_info->bit_rate = bit_rate;
179 p_sync_info->frame_size = frame_size;
180 p_adec->frame_size = frame_size;
185 int adec_DecodeFrame( adec_thread_t * p_adec, s16 * buffer )
187 int i_total_bytes_read;
189 /* parse audio data */
191 switch( (p_adec->header >> 17) & 3 )
195 if( (p_adec->header & 0xc0) == 0xc0 )
197 if( adec_layer2_mono (p_adec, buffer) )
204 if( adec_layer2_stereo (p_adec, buffer) )
213 if( (p_adec->header & 0xc0) == 0xc0 )
215 if( adec_layer1_mono (p_adec, buffer) )
222 if( adec_layer1_stereo (p_adec, buffer) )
230 /* Skip ancillary data */
232 if( (p_adec->header & 0xf000) == 0 ) /* free bitrate format */
237 RealignBits( &p_adec->bit_stream );
238 i_total_bytes_read = ( p_adec->i_read_bits + 7 ) / 8;
240 if( i_total_bytes_read > p_adec->frame_size )
242 return 1; /* overrun */
245 while( i_total_bytes_read++ < p_adec->frame_size )
247 RemoveBits( &p_adec->bit_stream, 8 ); /* skip ancillary data */