Split out a52 parsing functions into a52.h

modules/codec/a52.h

+/*****************************************************************************
+ * a52.h
+ *****************************************************************************
+ * Copyright (C) 2001-2009 Laurent Aimar
+ * $Id$
+ *
+ * Authors: Stéphane Borel <stef@via.ecp.fr>
+ *          Christophe Massiot <massiot@via.ecp.fr>
+ *          Gildas Bazin <gbazin@videolan.org>
+ *          Laurent Aimar <fenrir@via.ecp.fr>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
+ *****************************************************************************/
+
+#ifndef _VLC_A52_H
+#define _VLC_A52_H 1
+
+#include <vlc_aout.h>
+#include <vlc_bits.h>
+
+typedef struct
+{
+    unsigned int i_count;
+    unsigned int i_configuration;
+} vlc_a52_acmod_t;
+
+/**
+ * Minimum AC3 header size that vlc_a52_header_Parse needs.
+ */
+#define VLC_A52_HEADER_SIZE (8)
+
+/**
+ * AC3 header information.
+ */
+typedef struct
+{
+    bool b_eac3;
+
+    unsigned int i_channels;
+    unsigned int i_channels_conf;
+    unsigned int i_rate;
+    unsigned int i_bitrate;
+
+    unsigned int i_size;
+
+} vlc_a52_header_t;
+
+/**
+ * It parse AC3 sync info.
+ *
+ * This code is borrowed from liba52 by Aaron Holtzman & Michel Lespinasse,
+ * since we don't want to oblige S/PDIF people to use liba52 just to get
+ * their SyncInfo...
+ */
+static inline int vlc_a52_header_ParseAc3( vlc_a52_header_t *p_header,
+                                           const uint8_t *p_buf,
+                                           const vlc_a52_acmod_t *p_acmod )
+{
+    static const uint8_t pi_halfrate[12] = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 3 };
+    static const unsigned int pi_bitrate[] = { 32,  40,  48,  56,  64,  80,  96, 112,
+                                128, 160, 192, 224, 256, 320, 384, 448,
+                                512, 576, 640 };
+    static const uint8_t pi_lfeon[8] = { 0x10, 0x10, 0x04, 0x04,
+                                      0x04, 0x01, 0x04, 0x01 };
+
+    /* */
+    const unsigned i_rate_shift = pi_halfrate[p_buf[5] >> 3];
+
+    /* acmod, dsurmod and lfeon */
+    const unsigned i_acmod = p_buf[6] >> 5;
+    if( (p_buf[6] & 0xf8) == 0x50 )
+    {
+        /* Dolby surround = stereo + Dolby */
+        p_header->i_channels = 2;
+        p_header->i_channels_conf = AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT
+                            | AOUT_CHAN_DOLBYSTEREO;
+    }
+    else
+    {
+        p_header->i_channels      = p_acmod[i_acmod].i_count;
+        p_header->i_channels_conf = p_acmod[i_acmod].i_configuration;
+    }
+
+    if( p_buf[6] & pi_lfeon[i_acmod] )
+    {
+        p_header->i_channels++;
+        p_header->i_channels_conf |= AOUT_CHAN_LFE;
+    }
+
+    const unsigned i_frmsizecod = p_buf[4] & 63;
+    if( i_frmsizecod >= 38 )
+        return VLC_EGENERIC;
+    const unsigned i_bitrate_base = pi_bitrate[i_frmsizecod >> 1];
+    p_header->i_bitrate = (i_bitrate_base * 1000) >> i_rate_shift;
+
+    switch( p_buf[4] & 0xc0 )
+    {
+    case 0:
+        p_header->i_rate = 48000 >> i_rate_shift;
+        p_header->i_size = 4 * i_bitrate_base;
+        break;
+    case 0x40:
+        p_header->i_rate = 44100 >> i_rate_shift;
+        p_header->i_size = 2 * (320 * i_bitrate_base / 147 + (i_frmsizecod & 1));
+        break;
+    case 0x80:
+        p_header->i_rate = 32000 >> i_rate_shift;
+        p_header->i_size = 6 * i_bitrate_base;
+        break;
+    default:
+        return VLC_EGENERIC;
+    }
+    p_header->b_eac3 = false;
+    return VLC_SUCCESS;
+}
+
+/**
+ * It parse E-AC3 sync info
+ */
+static inline int vlc_a52_header_ParseEac3( vlc_a52_header_t *p_header,
+                                            const uint8_t *p_buf,
+                                            const vlc_a52_acmod_t *p_acmod )
+{
+    static const unsigned pi_samplerate[3] = { 48000, 44100, 32000 };
+    unsigned i_numblkscod;
+    bs_t s;
+
+
+    bs_init( &s, (void*)p_buf, VLC_A52_HEADER_SIZE );
+    bs_skip( &s, 16 +   /* start code */
+                 2 +    /* stream type */
+                 3 );   /* substream id */
+    const unsigned i_frame_size = bs_read( &s, 11 );
+    if( i_frame_size < 2 )
+        return VLC_EGENERIC;
+    p_header->i_size = 2 * ( i_frame_size + 1 );
+
+    const unsigned i_fscod = bs_read( &s, 2 );
+    if( i_fscod == 0x03 )
+    {
+        const unsigned i_fscod2 = bs_read( &s, 2 );
+        if( i_fscod2 == 0X03 )
+            return VLC_EGENERIC;
+        p_header->i_rate = pi_samplerate[i_fscod2] / 2;
+        i_numblkscod = 6;
+    }
+    else
+    {
+        static const int pi_blocks[4] = { 1, 2, 3, 6 };
+
+        p_header->i_rate = pi_samplerate[i_fscod];
+        i_numblkscod = pi_blocks[bs_read( &s, 2 )];
+    }
+
+    const unsigned i_acmod = bs_read( &s, 3 );
+    const unsigned i_lfeon = bs_read1( &s );
+
+    p_header->i_channels      = p_acmod[i_acmod].i_count + i_lfeon;
+    p_header->i_channels_conf = p_acmod[i_acmod].i_configuration | ( i_lfeon ? AOUT_CHAN_LFE : 0);
+    p_header->i_bitrate = 8 * p_header->i_size * (p_header->i_rate) / (i_numblkscod * 256);
+
+    p_header->b_eac3 = true;
+    return VLC_SUCCESS;
+}
+
+/**
+ * It will parse the header AC3 frame and fill vlc_a52_header_t* if
+ * it is valid or return VLC_EGENERIC.
+ *
+ * XXX It will only recognize big endian bitstream ie starting with 0x0b, 0x77
+ */
+static inline int vlc_a52_header_Parse( vlc_a52_header_t *p_header,
+                                        const uint8_t *p_buffer, int i_buffer )
+{
+    static const vlc_a52_acmod_t p_acmod[8] = {
+        { 2, AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT | AOUT_CHAN_DUALMONO },   /* Dual-channel 1+1 */
+        { 1, AOUT_CHAN_CENTER },                                        /* Mono 1/0 */
+        { 2, AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT },                        /* Stereo 2/0 */
+        { 3, AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT | AOUT_CHAN_CENTER },     /* 3F 3/0 */
+        { 3, AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT | AOUT_CHAN_REARCENTER }, /* 2F1R 2/1 */
+        { 4, AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT | AOUT_CHAN_CENTER |
+             AOUT_CHAN_REARCENTER },                                    /* 3F1R 3/1 */
+        { 5, AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT |
+             AOUT_CHAN_REARLEFT | AOUT_CHAN_REARRIGHT },                /* 2F2R 2/2 */
+        { 6, AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT | AOUT_CHAN_CENTER |
+             AOUT_CHAN_REARLEFT | AOUT_CHAN_REARRIGHT },                /* 3F2R 3/2 */
+    };
+
+    if( i_buffer < VLC_A52_HEADER_SIZE )
+        return VLC_EGENERIC;
+
+    /* Check synword */
+    if( p_buffer[0] != 0x0b || p_buffer[1] != 0x77 )
+        return VLC_EGENERIC;
+
+    /* Check bsid */
+    const int bsid = p_buffer[5] >> 3;
+    if( bsid > 16 )
+        return VLC_EGENERIC;
+
+    if( bsid <= 10 )
+    {
+        if( vlc_a52_header_ParseAc3( p_header, p_buffer, p_acmod ) )
+            return VLC_EGENERIC;
+    }
+    else
+    {
+        if( vlc_a52_header_ParseEac3( p_header, p_buffer, p_acmod ) )
+            return VLC_EGENERIC;
+    }
+    return VLC_SUCCESS;
+}
+
+#endif
+