lavf/matroskaenc: Check for valid metadata before creating tags

Tags must have at least one SimpleTag element to be spec conformant.
Updated lavf-mkv and seek-lavf-mkv FATE references as the tests were affected by
this.

Fixes ticket #2785

Signed-off-by: James Almer <jamrial@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
(cherry picked from commit 088ed5314694031e07e02e9d364c9d486a60e704)

Conflicts:
	tests/ref/lavf/mkv
	tests/ref/seek/lavf_mkv

3 files changed, 39 insertions, 27 deletions

diff --git a/libavformat/matroskaenc.c b/libavformat/matroskaenc.c
index 71236142dc..8b7c912dd4 100644
--- a/libavformat/matroskaenc.c
+++ b/libavformat/matroskaenc.c
@@ -793,6 +793,18 @@ static int mkv_write_tag(AVFormatContext *s, AVDictionary *m, unsigned int eleme
     return 0;
 }
 
+static int mkv_check_tag(AVDictionary *m)
+{
+    AVDictionaryEntry *t = NULL;
+    int ret = 0;
+
+    while ((t = av_dict_get(m, "", t, AV_DICT_IGNORE_SUFFIX)))
+        if (av_strcasecmp(t->key, "title") && av_strcasecmp(t->key, "stereo_mode"))
+            ret++;
+
+    return ret;
+}
+
 static int mkv_write_tags(AVFormatContext *s)
 {
     ebml_master tags = {0};
@@ -800,7 +812,7 @@ static int mkv_write_tags(AVFormatContext *s)
 
     ff_metadata_conv_ctx(s, ff_mkv_metadata_conv, NULL);
 
-    if (av_dict_get(s->metadata, "", NULL, AV_DICT_IGNORE_SUFFIX)) {
+    if (mkv_check_tag(s->metadata)) {
         ret = mkv_write_tag(s, s->metadata, 0, 0, &tags);
         if (ret < 0) return ret;
     }
@@ -808,7 +820,7 @@ static int mkv_write_tags(AVFormatContext *s)
     for (i = 0; i < s->nb_streams; i++) {
         AVStream *st = s->streams[i];
 
-        if (!av_dict_get(st->metadata, "", 0, AV_DICT_IGNORE_SUFFIX))
+        if (!mkv_check_tag(st->metadata))
             continue;
 
         ret = mkv_write_tag(s, st->metadata, MATROSKA_ID_TAGTARGETS_TRACKUID, i + 1, &tags);
@@ -818,7 +830,7 @@ static int mkv_write_tags(AVFormatContext *s)
     for (i = 0; i < s->nb_chapters; i++) {
         AVChapter *ch = s->chapters[i];
 
-        if (!av_dict_get(ch->metadata, "", NULL, AV_DICT_IGNORE_SUFFIX))
+        if (!mkv_check_tag(ch->metadata))
             continue;
 
         ret = mkv_write_tag(s, ch->metadata, MATROSKA_ID_TAGTARGETS_CHAPTERUID, ch->id, &tags);
diff --git a/tests/ref/lavf/mkv b/tests/ref/lavf/mkv
index 8820300100..33a5c18677 100644
--- a/tests/ref/lavf/mkv
+++ b/tests/ref/lavf/mkv
@@ -1,3 +1,3 @@
-796a3bbf2410e55e186367037bda6bb5 *./tests/data/lavf/lavf.mkv
-320297 ./tests/data/lavf/lavf.mkv
+32892841431db4b1149666cf94a8a714 *./tests/data/lavf/lavf.mkv
+320265 ./tests/data/lavf/lavf.mkv
 ./tests/data/lavf/lavf.mkv CRC=0x7065846b
diff --git a/tests/ref/seek/lavf_mkv b/tests/ref/seek/lavf_mkv
index ece15a1d75..02427cb1b9 100644
--- a/tests/ref/seek/lavf_mkv
+++ b/tests/ref/seek/lavf_mkv
@@ -1,48 +1,48 @@
-ret: 0         st: 1 flags:1 dts:-0.011000 pts:-0.011000 pos:    555 size:   208
+ret: 0         st: 1 flags:1 dts:-0.011000 pts:-0.011000 pos:    523 size:   208
 ret: 0         st:-1 flags:0  ts:-1.000000
-ret: 0         st: 1 flags:1 dts: 0.000000 pts: 0.000000 pos:    555 size:   208
+ret: 0         st: 1 flags:1 dts: 0.000000 pts: 0.000000 pos:    523 size:   208
 ret: 0         st:-1 flags:1  ts: 1.894167
-ret: 0         st: 0 flags:1 dts: 0.960000 pts: 0.960000 pos: 292185 size: 27834
+ret: 0         st: 0 flags:1 dts: 0.960000 pts: 0.960000 pos: 292153 size: 27834
 ret: 0         st: 0 flags:0  ts: 0.788000
-ret: 0         st: 0 flags:1 dts: 0.960000 pts: 0.960000 pos: 292185 size: 27834
+ret: 0         st: 0 flags:1 dts: 0.960000 pts: 0.960000 pos: 292153 size: 27834
 ret: 0         st: 0 flags:1  ts:-0.317000
-ret: 0         st: 1 flags:1 dts: 0.000000 pts: 0.000000 pos:    555 size:   208
+ret: 0         st: 1 flags:1 dts: 0.000000 pts: 0.000000 pos:    523 size:   208
 ret:-1         st: 1 flags:0  ts: 2.577000
 ret: 0         st: 1 flags:1  ts: 1.471000
-ret: 0         st: 1 flags:1 dts: 0.982000 pts: 0.982000 pos: 320026 size:   209
+ret: 0         st: 1 flags:1 dts: 0.982000 pts: 0.982000 pos: 319994 size:   209
 ret: 0         st:-1 flags:0  ts: 0.365002
-ret: 0         st: 0 flags:1 dts: 0.480000 pts: 0.480000 pos: 146738 size: 27925
+ret: 0         st: 0 flags:1 dts: 0.480000 pts: 0.480000 pos: 146706 size: 27925
 ret: 0         st:-1 flags:1  ts:-0.740831
-ret: 0         st: 1 flags:1 dts: 0.000000 pts: 0.000000 pos:    555 size:   208
+ret: 0         st: 1 flags:1 dts: 0.000000 pts: 0.000000 pos:    523 size:   208
 ret:-1         st: 0 flags:0  ts: 2.153000
 ret: 0         st: 0 flags:1  ts: 1.048000
-ret: 0         st: 0 flags:1 dts: 0.960000 pts: 0.960000 pos: 292185 size: 27834
+ret: 0         st: 0 flags:1 dts: 0.960000 pts: 0.960000 pos: 292153 size: 27834
 ret: 0         st: 1 flags:0  ts:-0.058000
-ret: 0         st: 1 flags:1 dts: 0.015000 pts: 0.015000 pos:    555 size:   208
+ret: 0         st: 1 flags:1 dts: 0.015000 pts: 0.015000 pos:    523 size:   208
 ret: 0         st: 1 flags:1  ts: 2.836000
-ret: 0         st: 1 flags:1 dts: 0.982000 pts: 0.982000 pos: 320026 size:   209
+ret: 0         st: 1 flags:1 dts: 0.982000 pts: 0.982000 pos: 319994 size:   209
 ret:-1         st:-1 flags:0  ts: 1.730004
 ret: 0         st:-1 flags:1  ts: 0.624171
-ret: 0         st: 0 flags:1 dts: 0.480000 pts: 0.480000 pos: 146738 size: 27925
+ret: 0         st: 0 flags:1 dts: 0.480000 pts: 0.480000 pos: 146706 size: 27925
 ret: 0         st: 0 flags:0  ts:-0.482000
-ret: 0         st: 1 flags:1 dts: 0.000000 pts: 0.000000 pos:    555 size:   208
+ret: 0         st: 1 flags:1 dts: 0.000000 pts: 0.000000 pos:    523 size:   208
 ret: 0         st: 0 flags:1  ts: 2.413000
-ret: 0         st: 0 flags:1 dts: 0.960000 pts: 0.960000 pos: 292185 size: 27834
+ret: 0         st: 0 flags:1 dts: 0.960000 pts: 0.960000 pos: 292153 size: 27834
 ret:-1         st: 1 flags:0  ts: 1.307000
 ret: 0         st: 1 flags:1  ts: 0.201000
-ret: 0         st: 1 flags:1 dts: 0.015000 pts: 0.015000 pos:    555 size:   208
+ret: 0         st: 1 flags:1 dts: 0.015000 pts: 0.015000 pos:    523 size:   208
 ret: 0         st:-1 flags:0  ts:-0.904994
-ret: 0         st: 1 flags:1 dts: 0.000000 pts: 0.000000 pos:    555 size:   208
+ret: 0         st: 1 flags:1 dts: 0.000000 pts: 0.000000 pos:    523 size:   208
 ret: 0         st:-1 flags:1  ts: 1.989173
-ret: 0         st: 0 flags:1 dts: 0.960000 pts: 0.960000 pos: 292185 size: 27834
+ret: 0         st: 0 flags:1 dts: 0.960000 pts: 0.960000 pos: 292153 size: 27834
 ret: 0         st: 0 flags:0  ts: 0.883000
-ret: 0         st: 0 flags:1 dts: 0.960000 pts: 0.960000 pos: 292185 size: 27834
+ret: 0         st: 0 flags:1 dts: 0.960000 pts: 0.960000 pos: 292153 size: 27834
 ret: 0         st: 0 flags:1  ts:-0.222000
-ret: 0         st: 1 flags:1 dts: 0.000000 pts: 0.000000 pos:    555 size:   208
+ret: 0         st: 1 flags:1 dts: 0.000000 pts: 0.000000 pos:    523 size:   208
 ret:-1         st: 1 flags:0  ts: 2.672000
 ret: 0         st: 1 flags:1  ts: 1.566000
-ret: 0         st: 1 flags:1 dts: 0.982000 pts: 0.982000 pos: 320026 size:   209
+ret: 0         st: 1 flags:1 dts: 0.982000 pts: 0.982000 pos: 319994 size:   209
 ret: 0         st:-1 flags:0  ts: 0.460008
-ret: 0         st: 0 flags:1 dts: 0.480000 pts: 0.480000 pos: 146738 size: 27925
+ret: 0         st: 0 flags:1 dts: 0.480000 pts: 0.480000 pos: 146706 size: 27925
 ret: 0         st:-1 flags:1  ts:-0.645825
-ret: 0         st: 1 flags:1 dts: 0.000000 pts: 0.000000 pos:    555 size:   208
+ret: 0         st: 1 flags:1 dts: 0.000000 pts: 0.000000 pos:    523 size:   208