matroskaenc: allow override of "writing application" tag

Signed-off-by: Tim Walker <tdskywalker@gmail.com>

CC: libav-stable@libav.org

libavformat/matroskaenc.c

@@ -805,7 +805,8 @@ static int mkv_write_tag(AVFormatContext *s, AVDictionary *m, unsigned int eleme
     end_ebml_master(s->pb, targets);
 
     while ((t = av_dict_get(m, "", t, AV_DICT_IGNORE_SUFFIX)))
-        if (av_strcasecmp(t->key, "title"))
+        if (av_strcasecmp(t->key, "title") &&
+            av_strcasecmp(t->key, "encoding_tool"))
             mkv_write_simpletag(s->pb, t);
 
     end_ebml_master(s->pb, tag);
@@ -965,7 +966,10 @@ static int mkv_write_header(AVFormatContext *s)
             segment_uid[i] = av_lfg_get(&lfg);
 
         put_ebml_string(pb, MATROSKA_ID_MUXINGAPP , LIBAVFORMAT_IDENT);
-        put_ebml_string(pb, MATROSKA_ID_WRITINGAPP, LIBAVFORMAT_IDENT);
+        if ((tag = av_dict_get(s->metadata, "encoding_tool", NULL, 0)))
+            put_ebml_string(pb, MATROSKA_ID_WRITINGAPP, tag->value);
+        else
+            put_ebml_string(pb, MATROSKA_ID_WRITINGAPP, LIBAVFORMAT_IDENT);
         put_ebml_binary(pb, MATROSKA_ID_SEGMENTUID, segment_uid, 16);
     }