Improve dealing with muxing/writing application of Matroska files

* Allow reading the current muxing/writing application
* Allow to preserve the original muxing/writing application instead of
  always overriding

abstractcontainer.cpp

@@ -7,7 +7,9 @@ using namespace CppUtilities;
 namespace TagParser {
 
 /// \brief The AbstractContainerPrivate struct contains private fields of the AbstractContainer class.
-struct AbstractContainerPrivate {};
+struct AbstractContainerPrivate {
+    std::vector<std::string> muxingApps, writingApps;
+};
 
 /*!
  * \class TagParser::AbstractContainer
@@ -475,6 +477,40 @@ bool AbstractContainer::supportsTitle() const
     return false;
 }
 
+/*!
+ * \brief Returns the muxing applications specified as meta-data.
+ */
+const std::vector<std::string> &AbstractContainer::muxingApplications() const
+{
+    static const auto empty = std::vector<std::string>();
+    return m_p ? m_p->muxingApps : empty;
+}
+
+/*!
+ * \brief Returns the muxing applications specified as meta-data.
+ */
+std::vector<std::string> &AbstractContainer::muxingApplications()
+{
+    return p()->muxingApps;
+}
+
+/*!
+ * \brief Returns the writing applications specified as meta-data.
+ */
+const std::vector<std::string> &AbstractContainer::writingApplications() const
+{
+    static const auto empty = std::vector<std::string>();
+    return m_p ? m_p->writingApps : empty;
+}
+
+/*!
+ * \brief Returns the writing applications specified as meta-data.
+ */
+std::vector<std::string> &AbstractContainer::writingApplications()
+{
+    return p()->writingApps;
+}
+
 /*!
  * \brief Returns the number of segments.
  */
@@ -502,4 +538,15 @@ void AbstractContainer::reset()
     m_titles.clear();
 }
 
+/*!
+ * \brief Returns the private data for the container.
+ */
+std::unique_ptr<AbstractContainerPrivate> &AbstractContainer::p()
+{
+    if (!m_p) {
+        m_p = std::make_unique<AbstractContainerPrivate>();
+    }
+    return m_p;
+}
+
 } // namespace TagParser

abstractcontainer.h

@@ -80,6 +80,8 @@ public:
     const std::vector<std::string> &titles() const;
     void setTitle(std::string_view title, std::size_t segmentIndex = 0);
     virtual bool supportsTitle() const;
+    const std::vector<std::string> &muxingApplications() const;
+    const std::vector<std::string> &writingApplications() const;
     virtual std::size_t segmentCount() const;
     CppUtilities::TimeSpan duration() const;
     CppUtilities::DateTime creationTime() const;
@@ -97,6 +99,8 @@ protected:
     virtual void internalParseChapters(Diagnostics &diag, AbortableProgressFeedback &progress);
     virtual void internalParseAttachments(Diagnostics &diag, AbortableProgressFeedback &progress);
     virtual void internalMakeFile(Diagnostics &diag, AbortableProgressFeedback &progress);
+    std::vector<std::string> &muxingApplications();
+    std::vector<std::string> &writingApplications();
 
     std::uint64_t m_version;
     std::uint64_t m_readVersion;
@@ -117,6 +121,8 @@ protected:
     bool m_attachmentsParsed;
 
 private:
+    std::unique_ptr<AbstractContainerPrivate> &p();
+
     std::uint64_t m_startOffset;
     std::iostream *m_stream;
     CppUtilities::BinaryReader m_reader;

matroska/matroskacontainer.cpp

@@ -627,6 +627,12 @@ void MatroskaContainer::parseSegmentInfo(Diagnostics &diag)
             case MatroskaIds::TimeCodeScale:
                 timeScale = subElement->readUInteger();
                 break;
+            case MatroskaIds::MuxingApp:
+                muxingApplications().emplace_back(subElement->readString());
+                break;
+            case MatroskaIds::WrittingApp:
+                writingApplications().emplace_back(subElement->readString());
+                break;
             }
             subElement = subElement->nextSibling();
         }
@@ -942,13 +948,18 @@ void MatroskaContainer::internalMakeFile(Diagnostics &diag, AbortableProgressFee
     const std::uint64_t ebmlHeaderSize = 4 + EbmlElement::calculateSizeDenotationLength(ebmlHeaderDataSize) + ebmlHeaderDataSize;
 
     // calculate size of "WritingLib"-element
-    constexpr std::string_view muxingAppName = APP_NAME " v" APP_VERSION;
-    constexpr std::uint64_t muxingAppElementTotalSize = 2 + 1 + muxingAppName.size();
+    const auto &muxingApps = const_cast<const MatroskaContainer *>(this)->muxingApplications();
+    const auto muxingAppName = (fileInfo().fileHandlingFlags() == MediaFileHandlingFlags::PreserveMuxingApplication && !muxingApps.empty())
+        ? std::string_view(muxingApps.front())
+        : std::string_view(APP_NAME " v" APP_VERSION);
+    const auto muxingAppElementTotalSize = std::uint64_t(2 + 1 + muxingAppName.size());
 
     // calculate size of "WritingApp"-element
-    const std::uint64_t writingAppElementDataSize
-        = fileInfo().writingApplication().empty() ? muxingAppName.size() : fileInfo().writingApplication().size();
-    const std::uint64_t writingAppElementTotalSize = 2 + 1 + writingAppElementDataSize;
+    const auto writingApps = const_cast<const MatroskaContainer *>(this)->writingApplications();
+    const auto writingAppName = (fileInfo().fileHandlingFlags() == MediaFileHandlingFlags::PreserveWritingApplication && !writingApps.empty())
+        ? std::string_view(writingApps.front())
+        : std::string_view(fileInfo().writingApplication().empty() ? muxingAppName : std::string_view(fileInfo().writingApplication()));
+    const auto writingAppElementTotalSize = std::uint64_t(2 + 1 + writingAppName.size());
 
     try {
         // calculate size of "Tags"-element

matroska/matroskaid.h

@@ -43,7 +43,7 @@ enum SeekIds { SeekID = 0x53AB, SeekPosition = 0x53AC };
 enum SegmentInfoIds {
     TimeCodeScale = 0x2AD7B1,
     Duration = 0x4489,
-    WrittingApp = 0x5741,
+    WrittingApp = 0x5741, // TODOv13: change to WritingApp
     MuxingApp = 0x4D80,
     DateUTC = 0x4461,
     SegmentUID = 0x73A4,

mediafileinfo.h

@@ -64,6 +64,8 @@ enum class MediaFileHandlingFlags : std::uint64_t {
     ForceIndexPosition = (1 << 3), /**< enforces the index position when applying changes, see remarks of MediaFileInfo::setIndexPosition() */
     NormalizeKnownTagFieldIds = (1 << 4), /**< normalizes known tag field IDs when parsing to match the tag specification's recommendations */
     PreserveRawTimingValues = (1 << 8), /**< preverves raw timing values (so far only used when making MP4 tracks) */
+    PreserveMuxingApplication = (1 << 9), /**< preverves the muxing application (so far only used when making Matroska container) */
+    PreserveWritingApplication = (1 << 10), /**< preverves the writing application (so far only used when making Matroska container) */
 };
 
 } // namespace TagParser
@@ -471,7 +473,9 @@ inline const std::string &MediaFileInfo::writingApplication() const
 
 /*!
  * \brief Sets the writing application as container-level meta-data. Put the name of your application here.
- * \remarks Might not be used (depends on the format).
+ * \remarks
+ * - Currently only used when making Matroska files.
+ * - The assigned value is ignored when MediaFileHandlingFlags::PreserveWritingApplication is set.
  */
 inline void MediaFileInfo::setWritingApplication(std::string_view writingApplication)
 {