vttdemux: add support for WebVTT chapters

Change-Id: If5e12ff7057ce4217907ef91d493e1bcd8a72656

mkvparser.cpp

@@ -4526,6 +4526,18 @@ long long Chapters::Atom::GetStopTimecode() const
 }
 
 
+long long Chapters::Atom::GetStartTime(const Chapters* pChapters) const
+{
+    return GetTime(pChapters, m_start_timecode);
+}
+
+
+long long Chapters::Atom::GetStopTime(const Chapters* pChapters) const
+{
+    return GetTime(pChapters, m_stop_timecode);
+}
+
+
 int Chapters::Atom::GetDisplayCount() const
 {
     return m_displays_count;
@@ -4651,6 +4663,37 @@ long Chapters::Atom::Parse(
 }
 
 
+long long Chapters::Atom::GetTime(
+    const Chapters* pChapters,
+    long long timecode)
+{
+    if (pChapters == NULL)
+        return -1;
+
+    Segment* const pSegment = pChapters->m_pSegment;
+
+    if (pSegment == NULL)  // weird
+        return -1;
+
+    const SegmentInfo* const pInfo = pSegment->GetInfo();
+
+    if (pInfo == NULL)
+        return -1;
+
+    const long long timecode_scale = pInfo->GetTimeCodeScale();
+
+    if (timecode_scale < 1)  // weird
+        return -1;
+
+    if (timecode < 0)
+        return -1;
+
+    const long long result = timecode_scale * timecode;
+
+    return result;
+}
+
+
 long Chapters::Atom::ParseDisplay(
     IMkvReader* pReader,
     long long pos,