From c7c26bb29781c21cbdfbb12a082fc8ba4a6337e6 Mon Sep 17 00:00:00 2001
From: Paul Gardiner <mythtv@glidos.net>
Date: Wed, 27 Dec 2023 14:46:54 +0000
Subject: [PATCH] Attempt to match forced track language to that of the
 selected main track

---
 mythtv/libs/libmythtv/decoders/decoderbase.cpp | 16 +++++++++++++++-
 mythtv/libs/libmythtv/decoders/decoderbase.h   |  2 +-
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/mythtv/libs/libmythtv/decoders/decoderbase.cpp b/mythtv/libs/libmythtv/decoders/decoderbase.cpp
index 6b07fe5ac21..012725e2339 100644
--- a/mythtv/libs/libmythtv/decoders/decoderbase.cpp
+++ b/mythtv/libs/libmythtv/decoders/decoderbase.cpp
@@ -975,6 +975,13 @@ int DecoderBase::SetTrack(uint Type, int TrackNo)
     {
         m_wantedTrack[Type]   = m_tracks[Type][static_cast<size_t>(m_currentTrack[Type])];
         m_selectedTrack[Type] = m_tracks[Type][static_cast<size_t>(m_currentTrack[Type])];
+        if (Type == kTrackTypeSubtitle)
+        {
+            // Rechoose the associated forced track, preferring the same language
+            int forcedTrackIndex = BestTrack(Type, true, m_selectedTrack[Type].m_language);
+            if (m_tracks[Type][forcedTrackIndex].m_forced)
+                m_selectedForcedTrack[Type] = m_tracks[Type][forcedTrackIndex];
+        }
     }
 
     return m_currentTrack[Type];
@@ -1047,11 +1054,14 @@ bool DecoderBase::InsertTrack(uint Type, const StreamInfo &Info)
  * Whether to favor or disfavor forced is controlled by the second
  * parameter.
  *
+ * A preferredlanguage can be specified as third parameter, which
+ * will override the user's preferrence list.
+ *
  * This function must not be called without taking m_trackLock
  *
  *  \return the highest weighted track, or -1 if none.
 */
-int DecoderBase::BestTrack(uint Type, bool forcedPreferred)
+int DecoderBase::BestTrack(uint Type, bool forcedPreferred, int preferredLanguage)
 {
     LOG(VB_PLAYBACK, LOG_INFO, LOC + QString("Trying to select track (w/lang & %1forced)")
         .arg(forcedPreferred ? "" : "!"));
@@ -1068,6 +1078,10 @@ int DecoderBase::BestTrack(uint Type, bool forcedPreferred)
                         m_tracks[Type][i].m_forced);
         int position = static_cast<int>(numStreams) - static_cast<int>(i);
         int language = 0;
+        if (preferredLanguage != 0 && m_tracks[Type][i].m_language == preferredLanguage)
+        {
+            language = static_cast<int>(m_languagePreference.size()) + 1;
+        }
         for (uint j = 0; (language == 0) && (j < m_languagePreference.size()); ++j)
         {
             if (m_tracks[Type][i].m_language == m_languagePreference[j])
diff --git a/mythtv/libs/libmythtv/decoders/decoderbase.h b/mythtv/libs/libmythtv/decoders/decoderbase.h
index 9f236dc8bff..4946f1d65eb 100644
--- a/mythtv/libs/libmythtv/decoders/decoderbase.h
+++ b/mythtv/libs/libmythtv/decoders/decoderbase.h
@@ -264,7 +264,7 @@ class DecoderBase
     static AVPixelFormat GetBestVideoFormat(AVPixelFormat* Formats, const VideoFrameTypes* RenderFormats);
 
   protected:
-    int          BestTrack(uint Type, bool forcedPreferred);
+    int          BestTrack(uint Type, bool forcedPreferred, int preferredLanguage = 0);
     virtual int  AutoSelectTrack(uint Type);
     void         AutoSelectTracks(void);
     void         ResetTracks(void);