Closed captions decoder.

The rollup and paint on mode is not really good (a lot of flicker) but
I don't see how to fix it (the subtitle is updated as soon as a new
character is added).

modules/codec/cc.h

+/*****************************************************************************
+ * cc.h
+ *****************************************************************************
+ * Copyright (C) 2007 Laurent Aimar
+ * $Id: csa.h 20134 2007-05-16 14:30:27Z jpsaman $
+ *
+ * Authors: 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 _CC_H
+#define _C_H 1
+
+/* CC have a maximum rate of 9600 bit/s (per field?) */
+#define CC_MAX_DATA_SIZE (2 * 3*600)
+typedef struct
+{
+    /* Which channel are present */
+    vlc_bool_t pb_present[4];
+
+    /* CC data per field
+     *  byte[x+0]: field (0/1)
+     *  byte[x+1]: cc data 1
+     *  byte[x+2]: cc data 2
+     */
+    int     i_data;
+    uint8_t p_data[CC_MAX_DATA_SIZE];
+} cc_data_t;
+
+static inline int cc_Channel( int i_field, const uint8_t p_data[2] )
+{
+    const uint8_t d = p_data[0] & 0x7f;
+    if( i_field != 0 && i_field != 1 )
+        return -1;
+    if( d == 0x14 )
+        return 2*i_field + 0;
+    else if( d == 0x1c )
+        return 2*i_field + 1;
+    /* unknown(middle of a command)  or not cc channel */
+    return -1;
+}
+static inline void cc_Init( cc_data_t *c )
+{
+    int i;
+
+    for( i = 0; i < 4; i++ )
+        c-> pb_present[i] = VLC_FALSE; 
+    c->i_data = 0;
+}
+static inline void cc_Exit( cc_data_t *c )
+{
+    return;
+}
+static inline void cc_Flush( cc_data_t *c )
+{
+    c->i_data = 0;
+}
+static inline void cc_Extract( cc_data_t *c, const uint8_t *p_src, int i_src )
+{
+    static const uint8_t p_cc_ga94[4] = { 0x47, 0x41, 0x39, 0x34 };
+    //static const uint8_t p_afd_start[4] = { 0x44, 0x54, 0x47, 0x31 };
+
+    if( i_src < 4 )
+        return;
+
+    /* cc_data()
+     *          u1 reserved(1)
+     *          u1 process_cc_data_flag
+     *          u1 additional_data_flag
+     *          u5 cc_count
+     *          u8 reserved(1111 1111)
+     *          for cc_count
+     *              u5 marker bit(1111 1)
+     *              u1 cc_valid
+     *              u2 cc_type
+     *              u8 cc_data_1
+     *              u8 cc_data_2
+     *          u8 marker bit(1111 1111)
+     *          if additional_data_flag
+     *              unknown
+     */
+    /* cc_type:
+     *  0x00: field 1
+     *  0x01: field 2
+     */
+    if( !memcmp( p_cc_ga94, p_src, 4 ) && i_src >= 5+1+1+1 && p_src[4] == 0x03 )
+    {
+        /* Extract CC from DVB/ATSC TS */
+        const uint8_t *cc = &p_src[5];
+        const int i_count_cc = cc[0]&0x1f;
+        int i;
+
+        if( !(cc[0]&0x40) ) // process flag
+            return;
+        if( i_src < 5 + 1+1 + i_count_cc*3 + 1)  // broken packet
+            return;
+        if( i_count_cc <= 0 )   // no cc present
+            return;
+        if( cc[2+i_count_cc * 3] != 0xff )  // marker absent
+            return;
+        cc += 2;
+
+        for( i = 0; i < i_count_cc; i++, cc += 3 )
+        {
+            int i_field = cc[0] & 0x03;
+            int i_channel;
+            if( ( cc[0] & 0xfc ) != 0xfc )
+                continue;
+            if( i_field != 0 && i_field != 1 )
+                continue;
+            if( c->i_data + 3 > CC_MAX_DATA_SIZE )
+                continue;
+
+            i_channel = cc_Channel( i_field, &cc[1] );
+            if( i_channel >= 0 && i_channel < 4 )
+                c->pb_present[i_channel] = VLC_TRUE;
+
+            c->p_data[c->i_data++] = i_field;
+            c->p_data[c->i_data++] = cc[1];
+            c->p_data[c->i_data++] = cc[2];
+        }
+    }
+    else
+    {
+        /* TODO DVD CC, ... */
+    }
+}
+
+#endif /* _CC_H */
+