[Bug 752847] New: matroska mux doesn't write user-supplied tags unless the 'streamable' property is set

[GStreamer (GNOME Bugzilla)]

https://bugzilla.gnome.org/show_bug.cgi?id=752847

            Bug ID: 752847
           Summary: matroska mux doesn't write user-supplied tags unless
                    the 'streamable' property is set
    Classification: Platform
           Product: GStreamer
           Version: unspecified
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: Normal
         Component: gst-plugins-good
          Assignee: gstreamer-bugs at lists.freedesktop.org
          Reporter: grd at loganmill.net
        QA Contact: gstreamer-bugs at lists.freedesktop.org
     GNOME version: ---

User-supplied tags are not written out unless 'streamable=true' is set. Easily
reproducible with gst-launch and mkvinfo.
We'll try to but the tag comment=hello into the x.mkv file:

$ gst-launch-1.0 videotestsrc ! taginject tags=comment=hello ! matroskamux !
filesink location=x.mkv
Setting pipeline to PAUSED ...
Pipeline is PREROLLING ...
Pipeline is PREROLLED ...
Setting pipeline to PLAYING ...
New clock: GstSystemClock
^Chandling interrupt.
Interrupt: Stopping pipeline ...
Execution ended after 0:00:03.699848471
Setting pipeline to PAUSED ...
Setting pipeline to READY ...
Setting pipeline to NULL ...
^C

$  mkvinfo x.mkv
+ EBML head
|+ Doc type: matroska
|+ Doc type version: 2
|+ Doc type read version: 2
+ Segment, size unknown
|+ Seek head (subentries will be skipped)
|+ Segment information
| + Segment UID: 0x12 0x21 0x11 0xd4 0x51 0x77 0xbe 0x8e 0xd1 0x31 0x26 0xa7
0x26 0x70 0x10 0x62
| + Timecode scale: 1000000
| + Duration: 0.000s (00:00:00.000)
| + Muxing application: GStreamer matroskamux version 1.5.2.1
| + Writing application: GStreamer Matroska muxer
| + Date: Fri Jul 24 23:05:15 2015 UTC
|+ Segment tracks
| + A track
|  + Track number: 1 (track ID for mkvmerge & mkvextract: 0)
|  + Track type: video
|  + Track UID: 2201393592170869641
|  + Default duration: 33.333ms (30.000 frames/fields per second for a video
track)
|  + Name: Video
|  + Video track
|   + Pixel width: 320
|   + Pixel height: 240
|   + Colour space: length 4, data: 0x49 0x34 0x32 0x30
|  + Codec ID: V_UNCOMPRESSED
|+ Cluster


...Note that the mkvinfo does not show the "comment" tag as being defined.
Rerun with the streamable property set:

$ gst-launch-1.0 videotestsrc ! taginject tags=comment=hello ! matroskamux
streamable=true ! filesink location=x.mkv


$ mkvinfo x.mkv
+ EBML head
|+ Doc type: matroska
|+ Doc type version: 2
|+ Doc type read version: 2
+ Segment, size unknown
|+ Tags
| + Tag
|  + Targets
|   + TrackUID: 127012133913909968
|  + Simple
|   + Name: COMMENTS
|   + String: hello
|+ Segment information
| + Segment UID: 0x3d 0x73 0xba 0x2e 0x51 0x16 0xc9 0x66 0x5f 0x7b 0x83 0x4a
0xdb 0x82 0x8d 0xac
| + Timecode scale: 1000000
| + Muxing application: GStreamer matroskamux version 1.5.2.1
| + Writing application: GStreamer Matroska muxer
| + Date: Fri Jul 24 23:15:12 2015 UTC
|+ Segment tracks
| + A track
|  + Track number: 1 (track ID for mkvmerge & mkvextract: 0)
|  + Track type: video
|  + Track UID: 127012133913909968
|  + Default duration: 33.333ms (30.000 frames/fields per second for a video
track)
|  + Name: Video
|  + Video track
|   + Pixel width: 320
|   + Pixel height: 240
|   + Colour space: length 4, data: 0x49 0x34 0x32 0x30
|  + Codec ID: V_UNCOMPRESSED
|+ Cluster

...and the 'hello' comment is set.

It seems that streams_tags are written by the following call in matroska-mux.c,
which is only invoked when streamable is true:

  if (mux->streamable) {
      ....
      gst_matroska_mux_write_streams_tags (mux);
      ...
  }

Disabling the mux->streamable conditional fixes the issue for me;

diff --git a/gst/matroska/matroska-mux.c b/gst/matroska/matroska-mux.c
index 9f79175..ff0971e 100644
--- a/gst/matroska/matroska-mux.c
+++ b/gst/matroska/matroska-mux.c
@@ -2729,7 +2729,8 @@ gst_matroska_mux_start (GstMatroskaMux * mux)
     gst_ebml_write_master_finish (ebml, master);
   }

-  if (mux->streamable) {
+  //  if (mux->streamable) {
+  if (1) {  // Write tags regardless of value of mux->streamable
     const GstTagList *tags;
     gboolean has_main_tags;

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