Support demuxing teletext in DVB streams.

Original patch by Francesco Lavra, francescolavra interfree it

Originally committed as revision 20414 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/avcodec.h

@@ -331,6 +331,7 @@ enum CodecID {
     CODEC_ID_SSA,
     CODEC_ID_MOV_TEXT,
     CODEC_ID_HDMV_PGS_SUBTITLE,
+    CODEC_ID_DVB_TELETEXT,
 
     /* other specific kind of codecs (generally used for attachments) */
     CODEC_ID_TTF= 0x18000,

libavformat/mpegts.c

@@ -535,6 +535,7 @@ static const StreamType DESC_types[] = {
     { 0x6a, CODEC_TYPE_AUDIO,             CODEC_ID_AC3 }, /* AC-3 descriptor */
     { 0x7a, CODEC_TYPE_AUDIO,            CODEC_ID_EAC3 }, /* E-AC-3 descriptor */
     { 0x7b, CODEC_TYPE_AUDIO,             CODEC_ID_DTS },
+    { 0x56, CODEC_TYPE_SUBTITLE, CODEC_ID_DVB_TELETEXT },
     { 0x59, CODEC_TYPE_SUBTITLE, CODEC_ID_DVB_SUBTITLE }, /* subtitling descriptor */
     { 0 },
 };
@@ -729,6 +730,13 @@ static void pmt_cb(MpegTSFilter *filter, const uint8_t *section, int section_len
                 mpegts_find_stream_type(st, desc_tag, DESC_types);
 
             switch(desc_tag) {
+            case 0x56: /* DVB teletext descriptor */
+                language[0] = get8(&p, desc_end);
+                language[1] = get8(&p, desc_end);
+                language[2] = get8(&p, desc_end);
+                language[3] = 0;
+                av_metadata_set(&st->metadata, "language", language);
+                break;
             case 0x59: /* subtitling descriptor */
                 language[0] = get8(&p, desc_end);
                 language[1] = get8(&p, desc_end);