Fix dvb subtitle decoding when display segment is missing.

libavcodec/dvbsubdec.c

@@ -1452,6 +1452,7 @@ static int dvbsub_decode(AVCodecContext *avctx,
     int page_id;
     int segment_length;
     int i;
+    int got_segment = 0;
 
     av_dlog(avctx, "DVB sub packet:\n");
 
@@ -1490,21 +1491,26 @@ static int dvbsub_decode(AVCodecContext *avctx,
             switch (segment_type) {
             case DVBSUB_PAGE_SEGMENT:
                 dvbsub_parse_page_segment(avctx, p, segment_length);
+                got_segment |= 1;
                 break;
             case DVBSUB_REGION_SEGMENT:
                 dvbsub_parse_region_segment(avctx, p, segment_length);
+                got_segment |= 2;
                 break;
             case DVBSUB_CLUT_SEGMENT:
                 dvbsub_parse_clut_segment(avctx, p, segment_length);
+                got_segment |= 4;
                 break;
             case DVBSUB_OBJECT_SEGMENT:
                 dvbsub_parse_object_segment(avctx, p, segment_length);
+                got_segment |= 8;
                 break;
             case DVBSUB_DISPLAYDEFINITION_SEGMENT:
                 dvbsub_parse_display_definition_segment(avctx, p, segment_length);
                 break;
             case DVBSUB_DISPLAY_SEGMENT:
                 *data_size = dvbsub_display_end_segment(avctx, p, segment_length, sub);
+                got_segment |= 16;
                 break;
             default:
                 av_dlog(avctx, "Subtitling segment type 0x%x, page id %d, length %d\n",
@@ -1515,6 +1521,10 @@ static int dvbsub_decode(AVCodecContext *avctx,
 
         p += segment_length;
     }
+    // Some streams do not send a display segment but if we have all the other
+    // segments then we need no further data.
+    if (got_segment == 15 && sub)
+        *data_size = dvbsub_display_end_segment(avctx, p, 0, sub);
 
     return p - buf;
 }