avformat/assenc: mux an event header if none are found in extradata

diff --git a/libavformat/assenc.c b/libavformat/assenc.c
index 13af86e8cf59a50f373003b78052f3b0e2340bc6..8593b6ca4d9a070913c01bc01ac60a11992ca173 100644 (file)
--- a/libavformat/assenc.c
+++ b/libavformat/assenc.c
@@ -54,6 +54,8 @@ static int write_header(AVFormatContext *s)
         if (avctx->extradata[avctx->extradata_size - 1] != '\n')
             avio_write(s->pb, "\r\n", 2);
     }
+    if (!strstr(avctx->extradata, "\n[Events]"))
+        avio_printf(s->pb, "[Events]\r\nFormat: Layer, Start, End, Style, Actor, MarginL, MarginR, MarginV, Effect, Text\r\n");
     avio_flush(s->pb);
 
     return 0;