Add links to upstream documentation of field IDs for the different formats

CMakeLists.txt

@@ -10,7 +10,7 @@ set(META_APP_URL "https://github.com/${META_APP_AUTHOR}/${META_PROJECT_NAME}")
 set(META_APP_DESCRIPTION "C++ library for reading and writing MP4 (iTunes), ID3, Vorbis, Opus, FLAC and Matroska tags")
 set(META_VERSION_MAJOR 9)
 set(META_VERSION_MINOR 1)
-set(META_VERSION_PATCH 3)
+set(META_VERSION_PATCH 4)
 set(META_REQUIRED_CPP_UNIT_VERSION 1.14.0)
 set(META_ADD_DEFAULT_CPP_UNIT_TEST_APPLICATION ON)
 

id3/id3v2frameids.cpp

@@ -13,6 +13,10 @@ namespace TagParser {
  * The short IDs start with "s" and the long IDs with "l". To convert between
  * these IDs the functions convertToShortId() and convertToLongId() can be
  * used.
+ *
+ * \sa
+ * - See https://id3.org/id3v2.3.0 for the specification of ID3v2.3.0 frame IDs.
+ * - See https://id3.org/id3v2.4.0-frames for the specification of ID3v2.4.0 frame IDs.
  */
 namespace Id3v2FrameIds {
 

matroska/matroskatagid.cpp

@@ -2,6 +2,10 @@
 
 using namespace std;
 
+/*!
+ * \brief Encapsulates Matroska tag IDs.
+ * \sa See https://matroska.org/technical/specs/tagging/index.html for a complete list of the officially supported Matroska tag names.
+ */
 namespace TagParser {
 
 namespace MatroskaTagIds {

matroska/matroskatagid.h

@@ -5,9 +5,6 @@
 
 namespace TagParser {
 
-/*!
- * \brief Encapsulates Matroska tag IDs.
- */
 namespace MatroskaTagIds {
 
 constexpr TAG_PARSER_EXPORT const char *original()

mp4/mp4ids.cpp

@@ -12,6 +12,7 @@ namespace Mp4AtomIds {
 
 /*!
  * \brief Encapsulates IDs of MP4 atoms holding tag information.
+ * \sa See http://atomicparsley.sourceforge.net/mpeg-4files.html for a table of known iTunes metadata atom IDs.
  */
 namespace Mp4TagAtomIds {
 }

vorbis/vorbiscommentids.h

@@ -6,7 +6,8 @@
 namespace TagParser {
 
 /*!
- * \brief Encapsulates Vorbis comment IDs.
+ * \brief Encapsulates Vorbis comment field names.
+ * \sa See https://xiph.org/vorbis/doc/v-comment.html for the upstream documentation of the field names.
  */
 namespace VorbisCommentIds {