Flag DVB subtitles for the hard hearing appropriately using their component_type id.

This is based on the component_type definition in the DVB SI spec [1].

[1]: http://www.dvb.org/technology/standards/a038_DVB-SI_dEN300468v1.12.1.pdfSigned-off-by: Ronald S. Bultje <rsbultje@gmail.com>
(cherry picked from commit 789936db)

libavformat/mpegts.c

@@ -935,7 +935,17 @@ int ff_parse_mpeg2_descriptor(AVFormatContext *fc, AVStream *st, int stream_type
         language[1] = get8(pp, desc_end);
         language[2] = get8(pp, desc_end);
         language[3] = 0;
-        get8(pp, desc_end);
+        /* hearing impaired subtitles detection */
+        switch(get8(pp, desc_end)) {
+        case 0x20: /* DVB subtitles (for the hard of hearing) with no monitor aspect ratio criticality */
+        case 0x21: /* DVB subtitles (for the hard of hearing) for display on 4:3 aspect ratio monitor */
+        case 0x22: /* DVB subtitles (for the hard of hearing) for display on 16:9 aspect ratio monitor */
+        case 0x23: /* DVB subtitles (for the hard of hearing) for display on 2.21:1 aspect ratio monitor */
+        case 0x24: /* DVB subtitles (for the hard of hearing) for display on a high definition monitor */
+        case 0x25: /* DVB subtitles (for the hard of hearing) with plano-stereoscopic disparity for display on a high definition monitor */
+            st->disposition |= AV_DISPOSITION_HEARING_IMPAIRED;
+            break;
+        }
         if (st->codec->extradata) {
             if (st->codec->extradata_size == 4 && memcmp(st->codec->extradata, *pp, 4))
                 av_log_ask_for_sample(fc, "DVB sub with multiple IDs\n");