Subtitles: Add initial forced subtitle support.

This enables forced subtitles when they are part of the current,
automatically selected subtitle stream (i.e. if your language is
English, an English subtitle track is automatically selected in the
existing code. Any forced subtitle detected will now be displayed).

I will add an OSD menu option to toggle forced subtitles.

This will not work for blu ray material where the forced subtitles are
on a different track entirely.

There are still some intermittent issues with DVD material that seem to
be related to the existing code. In these cases the forced subtitles may
no display.

mythtv/libs/libmythtv/avformatdecoder.cpp

@@ -3398,8 +3398,11 @@ bool AvFormatDecoder::ProcessSubtitlePacket(AVStream *curstream, AVPacket *pkt)
                 .arg(subtitle.start_display_time)
                 .arg(subtitle.end_display_time));
 
-        m_parent->GetSubReader(pkt->stream_index)->AddAVSubtitle(
-            subtitle, curstream->codec->codec_id == CODEC_ID_XSUB);
+        if (m_parent->GetSubReader(pkt->stream_index)->AddAVSubtitle(
+               subtitle, curstream->codec->codec_id == CODEC_ID_XSUB))
+        {
+            m_parent->EnableForcedSubtitles();
+        }
     }
 
     return true;

mythtv/libs/libmythtv/mythplayer.cpp

@@ -167,6 +167,7 @@ MythPlayer::MythPlayer(bool muted)
       ttPageNum(0x888),
       // Support for captions, teletext, etc. decoded by libav
       textDesired(false), enableCaptions(false), disableCaptions(false),
+      enableForcedSubtitles(false), allowForcedSubtitles(true),
       // CC608/708
       db_prefer708(true), cc608(this), cc708(this),
       // MHEG/MHI Interactive TV visible in OSD
@@ -1536,6 +1537,18 @@ void MythPlayer::EnableSubtitles(bool enable)
         disableCaptions = true;
 }
 
+void MythPlayer::DoEnableForcedSubtitles(void)
+{
+    enableForcedSubtitles = false;
+    if (!allowForcedSubtitles)
+        return;
+
+    osdLock.lock();
+    if (osd)
+        osd->InitSubtitles();
+    osdLock.unlock();
+}
+
 int MythPlayer::GetTrack(uint type)
 {
     if (decoder)
@@ -2603,6 +2616,10 @@ void MythPlayer::EventLoop(void)
     if (disableCaptions)
         SetCaptionsEnabled(false, false);
 
+    // enable forced subtitles if signalled by the decoder
+    if (enableForcedSubtitles)
+        DoEnableForcedSubtitles();
+
     // reset the scan (and hence deinterlacers) if triggered by the decoder
     if (resetScan != kScan_Ignore)
         SetScanType(resetScan);

mythtv/libs/libmythtv/mythplayer.h

@@ -258,6 +258,7 @@ class MTV_PUBLIC MythPlayer
     // Public Audio/Subtitle/EIA-608/EIA-708 stream selection - thread safe
     void TracksChanged(uint trackType);
     void EnableSubtitles(bool enable);
+    void EnableForcedSubtitles(void) { enableForcedSubtitles = true; }
 
     // Public MHEG/MHI stream selection
     bool SetAudioByComponentTag(int tag);
@@ -441,6 +442,7 @@ class MTV_PUBLIC MythPlayer
     int  ChangeTrack(uint type, int dir);
     void ChangeCaptionTrack(int dir);
     int  NextCaptionTrack(int mode);
+    void DoEnableForcedSubtitles(void);
 
     // Teletext Menu and non-NUV teletext decoder
     void EnableTeletext(int page = 0x100);
@@ -653,6 +655,8 @@ class MTV_PUBLIC MythPlayer
     bool      textDesired;
     bool      enableCaptions;
     bool      disableCaptions;
+    bool      enableForcedSubtitles;
+    bool      allowForcedSubtitles;
 
     // CC608/708
     bool db_prefer708;

mythtv/libs/libmythtv/subtitlereader.cpp

@@ -1,3 +1,4 @@
+#include "mythlogging.h"
 #include "subtitlereader.h"
 
 SubtitleReader::SubtitleReader()
@@ -28,18 +29,36 @@ void SubtitleReader::EnableRawTextSubtitles(bool enable)
     m_RawTextSubtitlesEnabled = enable;
 }
 
-void SubtitleReader::AddAVSubtitle(const AVSubtitle &subtitle,
+bool SubtitleReader::AddAVSubtitle(const AVSubtitle &subtitle,
                                    bool fix_position)
 {
-    if (!m_AVSubtitlesEnabled)
+    bool enableforced = false;
+    if (!m_AVSubtitlesEnabled && !subtitle.forced)
     {
         FreeAVSubtitle(subtitle);
-        return;
+        return enableforced;
     }
+
+    if (!m_AVSubtitlesEnabled && subtitle.forced)
+        enableforced = true;
+
+    bool clearsubs = false;
     m_AVSubtitles.lock.lock();
     m_AVSubtitles.fixPosition = fix_position;
     m_AVSubtitles.buffers.push_back(subtitle);
+    // in case forced subtitles aren't displayed, avoid leaking by
+    // manually clearing the subtitles
+    if (m_AVSubtitles.buffers.size() > 20)
+    {
+        LOG(VB_GENERAL, LOG_ERR, ">20 AVSubtitles queued - clearing.");
+        clearsubs = true;
+    }
     m_AVSubtitles.lock.unlock();
+
+    if (clearsubs)
+        ClearAVSubtitles();
+
+    return enableforced;
 }
 
 void SubtitleReader::ClearAVSubtitles(void)

mythtv/libs/libmythtv/subtitlereader.h

@@ -38,7 +38,7 @@ class SubtitleReader
     void EnableRawTextSubtitles(bool enable);
 
     AVSubtitles* GetAVSubtitles(void) { return &m_AVSubtitles; }
-    void AddAVSubtitle(const AVSubtitle& subtitle, bool fix_position);
+    bool AddAVSubtitle(const AVSubtitle& subtitle, bool fix_position);
     void ClearAVSubtitles(void);
     void FreeAVSubtitle(const AVSubtitle &sub);
 

mythtv/libs/libmythtv/subtitlescreen.cpp

@@ -88,9 +88,10 @@ bool SubtitleScreen::Create(void)
 void SubtitleScreen::Pulse(void)
 {
     ExpireSubtitles();
-    if (kDisplayAVSubtitle == m_subtitleType)
-        DisplayAVSubtitles();
-    else if (kDisplayTextSubtitle == m_subtitleType)
+
+    DisplayAVSubtitles(); // allow forced subtitles to work
+
+    if (kDisplayTextSubtitle == m_subtitleType)
         DisplayTextSubtitles();
     else if (kDisplayCC608 == m_subtitleType)
         DisplayCC608Subtitles();