avformat/webvttdec: Don't stop parsing on comments

Signed-off-by: Ricardo Constantino <wiiaboo@gmail.com>

libavformat/webvttdec.c

@@ -92,7 +92,8 @@ static int webvtt_read_header(AVFormatContext *s)
 
         /* ignore header chunk */
         if (!strncmp(p, "\xEF\xBB\xBFWEBVTT", 9) ||
-            !strncmp(p, "WEBVTT", 6))
+            !strncmp(p, "WEBVTT", 6) ||
+            !strncmp(p, "NOTE", 4))
             continue;
 
         /* optional cue identifier (can be a number like in SRT or some kind of

tests/ref/fate/sub-webvtt2

@@ -21,3 +21,4 @@ Dialogue: 0,0:00:43.00,0:00:46.00,Default,,0,0,0,,{\i1}キツネ{\i0}じゃな
 Dialogue: 0,0:00:50.00,0:00:55.00,Default,,0,0,0,,Some time ago in a rather distant place....
 Dialogue: 0,0:00:55.00,0:01:00.00,Default,,0,0,0,,Descending: 123456\NAscending: 123456
 Dialogue: 0,0:01:00.00,0:01:05.00,Default,,0,0,0,,>> Never gonna give you up Never gonna let you down\NNever\hgonna\hrun\haround & desert\hyou
+Dialogue: 0,0:55:00.00,1:00:00.00,Default,,0,0,0,,Transcrit par Célestes™