avformat/mpegts: set AV_DISPOSITION_DESCRIPTIONS for OIPF cases

1. an audio component with an ISO_639_language_descriptor in the PMT with the
audio_type field set to 0x03
2. a supplementary_audio_descriptor with the editorial_classification field set
to 0x01
3. an ac-3_descriptor or an enhanced_ac-3_descriptor with a component_type field
with the service_type flags set to Visually Impaired

Tested-by: Łukasz Krzciuk <lkrzciuk@vewd.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/mpegts.c

@@ -1835,6 +1835,7 @@ int ff_parse_mpeg2_descriptor(AVFormatContext *fc, AVStream *st, int stream_type
                 break;
             case 0x03:
                 st->disposition |= AV_DISPOSITION_VISUAL_IMPAIRED;
+                st->disposition |= AV_DISPOSITION_DESCRIPTIONS;
                 break;
             }
         }
@@ -1910,6 +1911,7 @@ int ff_parse_mpeg2_descriptor(AVFormatContext *fc, AVStream *st, int stream_type
             switch ((flags >> 2) & 0x1F) { /* editorial_classification */
             case 0x01:
                 st->disposition |= AV_DISPOSITION_VISUAL_IMPAIRED;
+                st->disposition |= AV_DISPOSITION_DESCRIPTIONS;
                 break;
             case 0x02:
                 st->disposition |= AV_DISPOSITION_HEARING_IMPAIRED;
@@ -1934,6 +1936,34 @@ int ff_parse_mpeg2_descriptor(AVFormatContext *fc, AVStream *st, int stream_type
             }
         }
         break;
+    case 0x6a: /* ac-3_descriptor */
+        {
+            int component_type_flag = get8(pp, desc_end) & (1 << 7);
+            if (component_type_flag) {
+                int component_type = get8(pp, desc_end);
+                int service_type_mask = 0x38;  // 0b00111000
+                int service_type = ((component_type & service_type_mask) >> 3);
+                if (service_type == 0x02 /* 0b010 */) {
+                    st->disposition |= AV_DISPOSITION_DESCRIPTIONS;
+                    av_log(ts->stream, AV_LOG_DEBUG, "New track disposition for id %u: %u\n", st->id, st->disposition);
+                }
+            }
+        }
+        break;
+    case 0x7a: /* enhanced_ac-3_descriptor */
+        {
+            int component_type_flag = get8(pp, desc_end) & (1 << 7);
+            if (component_type_flag) {
+                int component_type = get8(pp, desc_end);
+                int service_type_mask = 0x38;  // 0b00111000
+                int service_type = ((component_type & service_type_mask) >> 3);
+                if (service_type == 0x02 /* 0b010 */) {
+                    st->disposition |= AV_DISPOSITION_DESCRIPTIONS;
+                    av_log(ts->stream, AV_LOG_DEBUG, "New track disposition for id %u: %u\n", st->id, st->disposition);
+                }
+            }
+        }
+        break;
     default:
         break;
     }