From a310e7d120682d86a5b11066d729d8f0796127e4 Mon Sep 17 00:00:00 2001
From: Moritz Bunkus <moritz@bunkus.org>
Date: Mon, 29 Jun 2020 21:02:36 +0200
Subject: [PATCH] Matroska reader: fix `default track` flag handling
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Let's take a Matroska file with a subtitle track with its `default
track` set to `on`. When you remux that file, forcing that flag to off
via `--default-track …:no`, the first other track of the same
type (subtitles) that is read from a container which does not provide
such `default track` information (e.g. an SRT file) should have its
`default track` flag set.

Before this change this wasn't the case; the track from the SRT would
have its flag set to `no`. The Matroska reader was always signalling
"default track = yes` at the container level to the packetizer, even
if it was overridden via command line options. The flag would still be
set to `no` in the output file, but the fact that there was a `yes` at
the container level prevented `mkvmerge` from considering other tracks
which only had a priority of `track type`.

Fixes #2863.
---
 NEWS.md                                          | 11 +++++++++++
 src/input/r_matroska.cpp                         | 11 ++++++-----
 tests/results.txt                                |  1 +
 ...efault_track_forced_off_vs_default_by_type.rb | 16 ++++++++++++++++
 4 files changed, 34 insertions(+), 5 deletions(-)
 create mode 100755 tests/test-699default_track_forced_off_vs_default_by_type.rb

diff --git a/NEWS.md b/NEWS.md
index 85a5004a0..a069160e5 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -1,3 +1,14 @@
+# Version ?
+
+## Bug fixes
+
+* mkvmerge: Matroska reader: when reading tracks (e.g. a subtitle track) from
+  Matroska files with their `default track` flag set to `yes`, and when
+  overwriting those via the command line to `no`, `mkvmerge` would not promote
+  additional tracks of the same type from other files (e.g. another subtitle
+  track from an SRT file). Fixes #2863.
+
+
 # Version 48.0.0 "Sick Of Losing Soulmates" 2020-06-27
 
 ## New features and enhancements
diff --git a/src/input/r_matroska.cpp b/src/input/r_matroska.cpp
index 010c37e3e..ea52668a7 100644
--- a/src/input/r_matroska.cpp
+++ b/src/input/r_matroska.cpp
@@ -1649,11 +1649,12 @@ kax_reader_c::set_packetizer_headers(kax_track_t *t) {
   if (m_appending)
     return;
 
-  if (t->default_track)
-    PTZR(t->ptzr)->set_as_default_track(t->type == 'v' ? DEFTRACK_TYPE_VIDEO : t->type == 'a' ? DEFTRACK_TYPE_AUDIO : DEFTRACK_TYPE_SUBS, DEFAULT_TRACK_PRIORITY_FROM_SOURCE);
-
-  else if (!PTZR(t->ptzr)->m_ti.m_default_track.has_value())
-    PTZR(t->ptzr)->m_ti.m_default_track = false;
+  if (!PTZR(t->ptzr)->m_ti.m_default_track.has_value()) {
+    if (t->default_track)
+      PTZR(t->ptzr)->set_as_default_track(t->type == 'v' ? DEFTRACK_TYPE_VIDEO : t->type == 'a' ? DEFTRACK_TYPE_AUDIO : DEFTRACK_TYPE_SUBS, DEFAULT_TRACK_PRIORITY_FROM_SOURCE);
+    else
+      PTZR(t->ptzr)->m_ti.m_default_track = false;
+  }
 
   if (t->forced_track && !PTZR(t->ptzr)->m_ti.m_forced_track.has_value())
     PTZR(t->ptzr)->set_track_forced_flag(true);
diff --git a/tests/results.txt b/tests/results.txt
index 640d850c0..0e0b814c3 100644
--- a/tests/results.txt
+++ b/tests/results.txt
@@ -544,3 +544,4 @@ T_695mpeg_ts_single_h264_frame_with_unbounded_pes_size:a97c491d719a6228d593e6d67
 T_696wavpack5:167606e4e11fef79a9cb859a371d4d8a-009b8b5a53f51ddf0f8fd3be3bf808cb-167606e4e11fef79a9cb859a371d4d8a:passed:20200617-144644:0.079896556
 T_697dts_es_xch:true:passed:20200622-160456:0.0
 T_698ac3_dolby_surround_ex:true-true-true:passed:20200622-173931:0.051167592
+T_699default_track_forced_off_vs_default_by_type:59aea3a8b7c10b1e64e6e241f2dc979c-true-59aea3a8b7c10b1e64e6e241f2dc979c-true-c4e85aed908bbe688fe6949c442cdbba-true:passed:20200629-201706:0.073934952
diff --git a/tests/test-699default_track_forced_off_vs_default_by_type.rb b/tests/test-699default_track_forced_off_vs_default_by_type.rb
new file mode 100755
index 000000000..72e83997e
--- /dev/null
+++ b/tests/test-699default_track_forced_off_vs_default_by_type.rb
@@ -0,0 +1,16 @@
+#!/usr/bin/ruby -w
+
+# T_699default_track_forced_off_vs_default_by_type
+describe "mkvmerge / Matroska file with 'default track' set, overwritten on command line, track from additional SRT file should become default"
+
+file_names = "data/mkv/sub-is-default.mks data/subtitles/srt/ven.srt"
+specs      = [ [ "", true, false ], [ "--default-track 0:yes", true, false ], [ "--default-track 0:no", false, true ] ]
+
+specs.each do |spec|
+  test_merge file_names, :args => spec[0], :keep_tmp => true
+
+  test "#{spec}" do
+    json = identify_json(tmp)
+    (json["tracks"][0]["properties"]["default_track"] == spec[1]) && (json["tracks"][1]["properties"]["default_track"] == spec[2])
+  end
+end