1 /*****************************************************************************
2 * adec_generic.c: MPEG audio decoder
3 *****************************************************************************
4 * Copyright (C) 1999-2001 VideoLAN
5 * $Id: mpeg_adec_generic.c,v 1.2 2001/11/28 15:08:05 massiot 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 *****************************************************************************/
27 #include <string.h> /* memcpy(), memset() */
36 #include "modules_export.h" /* Used for exporting vlc symbols to plugins */
38 #include "input_ext-dec.h"
39 #include "stream_control.h"
41 #include "mpeg_adec_generic.h"
42 #include "mpeg_adec.h"
43 #include "adec_math.h" /* DCT32(), PCM() */
44 #include "adec_layer1.h"
45 #include "adec_layer2.h"
47 int adec_Init( adec_thread_t * p_adec )
49 p_adec->bank_0.actual = p_adec->bank_0.v1;
50 p_adec->bank_0.pos = 0;
51 p_adec->bank_1.actual = p_adec->bank_1.v1;
52 p_adec->bank_1.pos = 0;
56 int adec_SyncFrame( adec_thread_t * p_adec, adec_sync_info_t * p_sync_info )
58 static int mpeg1_sample_rate[3] = {44100, 48000, 32000};
59 static int mpeg1_layer1_bit_rate[15] =
61 0, 32, 64, 96, 128, 160, 192, 224, 256, 288, 320, 352, 384, 416, 448
63 static int mpeg1_layer2_bit_rate[15] =
65 0, 32, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320, 384
67 static int mpeg2_layer1_bit_rate[15] =
69 0, 32, 48, 56, 64, 80, 96, 112, 128, 144, 160, 176, 192, 224, 256
71 static int mpeg2_layer2_bit_rate[15] =
73 0, 8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160
75 static int * bit_rate_table[8] =
77 NULL, NULL, mpeg2_layer2_bit_rate, mpeg2_layer1_bit_rate,
78 NULL, NULL, mpeg1_layer2_bit_rate, mpeg1_layer1_bit_rate
88 /* We read the whole header, but only really take 8 bits */
89 header = GetBits( &p_adec->bit_stream, 8 ) << 24;
90 header |= ShowBits( &p_adec->bit_stream, 24 );
92 p_adec->header = header;
94 /* basic header check : sync word */
95 if( (header & 0xfff00000) != 0xfff00000 )
100 /* calculate bit rate */
101 index = ( header >> 17 ) & 7; /* mpeg ID + layer */
102 bit_rates = bit_rate_table[ index ];
103 if( bit_rates == NULL )
105 return 1; /* invalid layer */
108 index = ( header >> 12 ) & 15; /* bit rate index */
113 bit_rate = bit_rates[ index ];
115 /* mpeg 1 layer 2 : check that bitrate per channel is valid */
117 if( bit_rates == mpeg1_layer2_bit_rate )
119 if( (header & 0xc0) == 0xc0 )
123 return 1; /* invalid bitrate per channel */
128 if( (1 << index) & 0x2e )
130 return 1; /* invalid bitrate per channel */
135 /* calculate sample rate */
137 index = ( header >> 10 ) & 3; /* sample rate index */
143 sample_rate = mpeg1_sample_rate[ index ];
145 if( ! (header & 0x80000) )
147 sample_rate >>= 1; /* half sample rate for mpeg2 */
150 /* calculate frame length */
152 if( (header & 0x60000) == 0x60000 )
155 frame_size = 48000 * bit_rate / sample_rate;
166 frame_size = 144000 * bit_rate / sample_rate;
175 /* Now we are sure we want this header, read it */
176 RemoveBits( &p_adec->bit_stream, 24 );
177 p_adec->i_read_bits = 32;
179 p_sync_info->sample_rate = sample_rate;
180 p_sync_info->bit_rate = bit_rate;
181 p_sync_info->frame_size = frame_size;
182 p_adec->frame_size = frame_size;
187 int adec_DecodeFrame( adec_thread_t * p_adec, s16 * buffer )
189 int i_total_bytes_read;
191 if( ! (p_adec->header & 0x10000) )
193 /* Error check, skip it */
194 RemoveBits( &p_adec->bit_stream, 16 );
195 p_adec->i_read_bits += 16;
198 /* parse audio data */
200 switch( (p_adec->header >> 17) & 3 )
204 if( (p_adec->header & 0xc0) == 0xc0 )
206 if( adec_layer2_mono (p_adec, buffer) )
213 if( adec_layer2_stereo (p_adec, buffer) )
222 if( (p_adec->header & 0xc0) == 0xc0 )
224 if( adec_layer1_mono (p_adec, buffer) )
231 if( adec_layer1_stereo (p_adec, buffer) )
239 /* Skip ancillary data */
241 if( (p_adec->header & 0xf000) == 0 ) /* free bitrate format */
246 RealignBits( &p_adec->bit_stream );
247 i_total_bytes_read = ( p_adec->i_read_bits + 7 ) / 8;
249 if( i_total_bytes_read > p_adec->frame_size )
251 return 1; /* overrun */
254 while( i_total_bytes_read++ < p_adec->frame_size )
256 RemoveBits( &p_adec->bit_stream, 8 ); /* skip ancillary data */