Fix extensibility of ID3v2 FrameFactory

Because the main extension point of FrameFactory was using a protected Frame subclass, it was not really possible to implement a custom frame factory. Existing Frame subclasses also show that access to the frame header might be needed when implementing a Frame subclass.
2026-07-23 20:00:56 -04:00 · 2023-11-18 07:14:32 +01:00
parent 59166f6757
commit 3d67b139e4
9 changed files with 643 additions and 247 deletions
--- a/taglib/mpeg/id3v2/frames/textidentificationframe.cpp
+++ b/taglib/mpeg/id3v2/frames/textidentificationframe.cpp
@@ -135,6 +135,21 @@ namespace
    std::pair("DJ-MIX", "DJMIXER"),
    std::pair("MIX", "MIXER"),
  };
+
+  constexpr std::array txxxFrameTranslation {
+    std::pair("MUSICBRAINZ ALBUM ID", "MUSICBRAINZ_ALBUMID"),
+    std::pair("MUSICBRAINZ ARTIST ID", "MUSICBRAINZ_ARTISTID"),
+    std::pair("MUSICBRAINZ ALBUM ARTIST ID", "MUSICBRAINZ_ALBUMARTISTID"),
+    std::pair("MUSICBRAINZ ALBUM RELEASE COUNTRY", "RELEASECOUNTRY"),
+    std::pair("MUSICBRAINZ ALBUM STATUS", "RELEASESTATUS"),
+    std::pair("MUSICBRAINZ ALBUM TYPE", "RELEASETYPE"),
+    std::pair("MUSICBRAINZ RELEASE GROUP ID", "MUSICBRAINZ_RELEASEGROUPID"),
+    std::pair("MUSICBRAINZ RELEASE TRACK ID", "MUSICBRAINZ_RELEASETRACKID"),
+    std::pair("MUSICBRAINZ WORK ID", "MUSICBRAINZ_WORKID"),
+    std::pair("ACOUSTID ID", "ACOUSTID_ID"),
+    std::pair("ACOUSTID FINGERPRINT", "ACOUSTID_FINGERPRINT"),
+    std::pair("MUSICIP PUID", "MUSICIP_PUID"),
+  };
 }  // namespace

 const KeyConversionMap &TextIdentificationFrame::involvedPeopleMap() // static
@@ -432,6 +447,26 @@ UserTextIdentificationFrame *UserTextIdentificationFrame::find(
  return nullptr;
 }

+String UserTextIdentificationFrame::txxxToKey(const String &description)
+{
+  const String d = description.upper();
+  for(const auto &[o, t] : txxxFrameTranslation) {
+    if(d == o)
+      return t;
+  }
+  return d;
+}
+
+String UserTextIdentificationFrame::keyToTXXX(const String &s)
+{
+  const String key = s.upper();
+  for(const auto &[o, t] : txxxFrameTranslation) {
+    if(key == t)
+      return o;
+  }
+  return s;
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 // UserTextIdentificationFrame private members
 ////////////////////////////////////////////////////////////////////////////////
--- a/taglib/mpeg/id3v2/frames/textidentificationframe.h
+++ b/taglib/mpeg/id3v2/frames/textidentificationframe.h
@@ -301,6 +301,16 @@ namespace TagLib {
       */
      static UserTextIdentificationFrame *find(Tag *tag, const String &description);

+      /*!
+       * Returns an appropriate TXXX frame description for the given free-form tag key.
+       */
+      static String keyToTXXX(const String &);
+
+      /*!
+       * Returns a free-form tag name for the given ID3 frame description.
+       */
+      static String txxxToKey(const String &);
+
    private:
      UserTextIdentificationFrame(const ByteVector &data, Header *h);
      UserTextIdentificationFrame(const TextIdentificationFrame &);
--- a/taglib/mpeg/id3v2/id3v2frame.cpp
+++ b/taglib/mpeg/id3v2/id3v2frame.cpp
@@ -97,56 +97,6 @@ unsigned int Frame::headerSize()
  return d->header->size();
 }

-Frame *Frame::createTextualFrame(const String &key, const StringList &values) //static
-{
-  // check if the key is contained in the key<=>frameID mapping
-  ByteVector frameID = keyToFrameID(key);
-  if(!frameID.isEmpty()) {
-    // Apple proprietary WFED (Podcast URL), MVNM (Movement Name), MVIN (Movement Number), GRP1 (Grouping) are in fact text frames.
-    if(frameID[0] == 'T' || frameID == "WFED" || frameID == "MVNM" || frameID == "MVIN" || frameID == "GRP1"){ // text frame
-      auto frame = new TextIdentificationFrame(frameID, String::UTF8);
-      frame->setText(values);
-      return frame;
-    } if((frameID[0] == 'W') && (values.size() == 1)){  // URL frame (not WXXX); support only one value
-        auto frame = new UrlLinkFrame(frameID);
-        frame->setUrl(values.front());
-        return frame;
-    } if(frameID == "PCST") {
-      return new PodcastFrame();
-    }
-  }
-  if(key == "MUSICBRAINZ_TRACKID" && values.size() == 1) {
-    auto frame = new UniqueFileIdentifierFrame("http://musicbrainz.org", values.front().data(String::UTF8));
-    return frame;
-  }
-  // now we check if it's one of the "special" cases:
-  // -LYRICS: depending on the number of values, use USLT or TXXX (with description=LYRICS)
-  if((key == "LYRICS" || key.startsWith(lyricsPrefix)) && values.size() == 1){
-    auto frame = new UnsynchronizedLyricsFrame(String::UTF8);
-    frame->setDescription(key == "LYRICS" ? key : key.substr(lyricsPrefix.size()));
-    frame->setText(values.front());
-    return frame;
-  }
-  // -URL: depending on the number of values, use WXXX or TXXX (with description=URL)
-  if((key == "URL" || key.startsWith(urlPrefix)) && values.size() == 1){
-    auto frame = new UserUrlLinkFrame(String::UTF8);
-    frame->setDescription(key == "URL" ? key : key.substr(urlPrefix.size()));
-    frame->setUrl(values.front());
-    return frame;
-  }
-  // -COMMENT: depending on the number of values, use COMM or TXXX (with description=COMMENT)
-  if((key == "COMMENT" || key.startsWith(commentPrefix)) && values.size() == 1){
-    auto frame = new CommentsFrame(String::UTF8);
-    if (key != "COMMENT"){
-      frame->setDescription(key.substr(commentPrefix.size()));
-    }
-    frame->setText(values.front());
-    return frame;
-  }
-  // if none of the above cases apply, we use a TXXX frame with the key as description
-  return new UserTextIdentificationFrame(keyToTXXX(key), values, String::UTF8);
-}
-
 Frame::~Frame() = default;

 ByteVector Frame::frameID() const
@@ -181,6 +131,125 @@ ByteVector Frame::render() const
  return headerData + fieldData;
 }

+Frame::Header *Frame::header() const
+{
+  return d->header;
+}
+
+namespace
+{
+  constexpr std::array frameTranslation {
+    // Text information frames
+    std::pair("TALB", "ALBUM"),
+    std::pair("TBPM", "BPM"),
+    std::pair("TCOM", "COMPOSER"),
+    std::pair("TCON", "GENRE"),
+    std::pair("TCOP", "COPYRIGHT"),
+    std::pair("TDEN", "ENCODINGTIME"),
+    std::pair("TDLY", "PLAYLISTDELAY"),
+    std::pair("TDOR", "ORIGINALDATE"),
+    std::pair("TDRC", "DATE"),
+    // std::pair("TRDA", "DATE"), // id3 v2.3, replaced by TDRC in v2.4
+    // std::pair("TDAT", "DATE"), // id3 v2.3, replaced by TDRC in v2.4
+    // std::pair("TYER", "DATE"), // id3 v2.3, replaced by TDRC in v2.4
+    // std::pair("TIME", "DATE"), // id3 v2.3, replaced by TDRC in v2.4
+    std::pair("TDRL", "RELEASEDATE"),
+    std::pair("TDTG", "TAGGINGDATE"),
+    std::pair("TENC", "ENCODEDBY"),
+    std::pair("TEXT", "LYRICIST"),
+    std::pair("TFLT", "FILETYPE"),
+    // std::pair("TIPL", "INVOLVEDPEOPLE"), handled separately
+    std::pair("TIT1", "WORK"), // 'Work' in iTunes
+    std::pair("TIT2", "TITLE"),
+    std::pair("TIT3", "SUBTITLE"),
+    std::pair("TKEY", "INITIALKEY"),
+    std::pair("TLAN", "LANGUAGE"),
+    std::pair("TLEN", "LENGTH"),
+    // std::pair("TMCL", "MUSICIANCREDITS"), handled separately
+    std::pair("TMED", "MEDIA"),
+    std::pair("TMOO", "MOOD"),
+    std::pair("TOAL", "ORIGINALALBUM"),
+    std::pair("TOFN", "ORIGINALFILENAME"),
+    std::pair("TOLY", "ORIGINALLYRICIST"),
+    std::pair("TOPE", "ORIGINALARTIST"),
+    std::pair("TOWN", "OWNER"),
+    std::pair("TPE1", "ARTIST"),
+    std::pair("TPE2", "ALBUMARTIST"), // id3's spec says 'PERFORMER', but most programs use 'ALBUMARTIST'
+    std::pair("TPE3", "CONDUCTOR"),
+    std::pair("TPE4", "REMIXER"),     // could also be ARRANGER
+    std::pair("TPOS", "DISCNUMBER"),
+    std::pair("TPRO", "PRODUCEDNOTICE"),
+    std::pair("TPUB", "LABEL"),
+    std::pair("TRCK", "TRACKNUMBER"),
+    std::pair("TRSN", "RADIOSTATION"),
+    std::pair("TRSO", "RADIOSTATIONOWNER"),
+    std::pair("TSOA", "ALBUMSORT"),
+    std::pair("TSOC", "COMPOSERSORT"),
+    std::pair("TSOP", "ARTISTSORT"),
+    std::pair("TSOT", "TITLESORT"),
+    std::pair("TSO2", "ALBUMARTISTSORT"), // non-standard, used by iTunes
+    std::pair("TSRC", "ISRC"),
+    std::pair("TSSE", "ENCODING"),
+    std::pair("TSST", "DISCSUBTITLE"),
+    // URL frames
+    std::pair("WCOP", "COPYRIGHTURL"),
+    std::pair("WOAF", "FILEWEBPAGE"),
+    std::pair("WOAR", "ARTISTWEBPAGE"),
+    std::pair("WOAS", "AUDIOSOURCEWEBPAGE"),
+    std::pair("WORS", "RADIOSTATIONWEBPAGE"),
+    std::pair("WPAY", "PAYMENTWEBPAGE"),
+    std::pair("WPUB", "PUBLISHERWEBPAGE"),
+    // std::pair("WXXX", "URL"), handled specially
+    // Other frames
+    std::pair("COMM", "COMMENT"),
+    // std::pair("USLT", "LYRICS"), handled specially
+    // Apple iTunes proprietary frames
+    std::pair("PCST", "PODCAST"),
+    std::pair("TCAT", "PODCASTCATEGORY"),
+    std::pair("TDES", "PODCASTDESC"),
+    std::pair("TGID", "PODCASTID"),
+    std::pair("WFED", "PODCASTURL"),
+    std::pair("MVNM", "MOVEMENTNAME"),
+    std::pair("MVIN", "MOVEMENTNUMBER"),
+    std::pair("GRP1", "GROUPING"),
+    std::pair("TCMP", "COMPILATION"),
+  };
+
+  // list of deprecated frames and their successors
+  constexpr std::array deprecatedFrames {
+    std::pair("TRDA", "TDRC"), // 2.3 -> 2.4 (http://en.wikipedia.org/wiki/ID3)
+    std::pair("TDAT", "TDRC"), // 2.3 -> 2.4
+    std::pair("TYER", "TDRC"), // 2.3 -> 2.4
+    std::pair("TIME", "TDRC"), // 2.3 -> 2.4
+  };
+}  // namespace
+
+String Frame::frameIDToKey(const ByteVector &id)
+{
+  ByteVector id24 = id;
+  for(const auto &[o, t] : deprecatedFrames) {
+    if(id24 == o) {
+      id24 = t;
+      break;
+    }
+  }
+  for(const auto &[o, t] : frameTranslation) {
+    if(id24 == o)
+      return t;
+  }
+  return String();
+}
+
+ByteVector Frame::keyToFrameID(const String &s)
+{
+  const String key = s.upper();
+  for(const auto &[o, t] : frameTranslation) {
+    if(key == t)
+      return o;
+  }
+  return ByteVector();
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 // protected members
 ////////////////////////////////////////////////////////////////////////////////
@@ -197,11 +266,6 @@ Frame::Frame(Header *h) :
  d->header = h;
 }

-Frame::Header *Frame::header() const
-{
-  return d->header;
-}
-
 void Frame::setHeader(Header *h, bool deleteCurrent)
 {
  if(deleteCurrent)
@@ -296,155 +360,6 @@ String::Type Frame::checkTextEncoding(const StringList &fields, String::Type enc
  return String::Latin1;
 }

-namespace
-{
-  constexpr std::array frameTranslation {
-    // Text information frames
-    std::pair("TALB", "ALBUM"),
-    std::pair("TBPM", "BPM"),
-    std::pair("TCOM", "COMPOSER"),
-    std::pair("TCON", "GENRE"),
-    std::pair("TCOP", "COPYRIGHT"),
-    std::pair("TDEN", "ENCODINGTIME"),
-    std::pair("TDLY", "PLAYLISTDELAY"),
-    std::pair("TDOR", "ORIGINALDATE"),
-    std::pair("TDRC", "DATE"),
-    // std::pair("TRDA", "DATE"), // id3 v2.3, replaced by TDRC in v2.4
-    // std::pair("TDAT", "DATE"), // id3 v2.3, replaced by TDRC in v2.4
-    // std::pair("TYER", "DATE"), // id3 v2.3, replaced by TDRC in v2.4
-    // std::pair("TIME", "DATE"), // id3 v2.3, replaced by TDRC in v2.4
-    std::pair("TDRL", "RELEASEDATE"),
-    std::pair("TDTG", "TAGGINGDATE"),
-    std::pair("TENC", "ENCODEDBY"),
-    std::pair("TEXT", "LYRICIST"),
-    std::pair("TFLT", "FILETYPE"),
-    // std::pair("TIPL", "INVOLVEDPEOPLE"), handled separately
-    std::pair("TIT1", "WORK"), // 'Work' in iTunes
-    std::pair("TIT2", "TITLE"),
-    std::pair("TIT3", "SUBTITLE"),
-    std::pair("TKEY", "INITIALKEY"),
-    std::pair("TLAN", "LANGUAGE"),
-    std::pair("TLEN", "LENGTH"),
-    // std::pair("TMCL", "MUSICIANCREDITS"), handled separately
-    std::pair("TMED", "MEDIA"),
-    std::pair("TMOO", "MOOD"),
-    std::pair("TOAL", "ORIGINALALBUM"),
-    std::pair("TOFN", "ORIGINALFILENAME"),
-    std::pair("TOLY", "ORIGINALLYRICIST"),
-    std::pair("TOPE", "ORIGINALARTIST"),
-    std::pair("TOWN", "OWNER"),
-    std::pair("TPE1", "ARTIST"),
-    std::pair("TPE2", "ALBUMARTIST"), // id3's spec says 'PERFORMER', but most programs use 'ALBUMARTIST'
-    std::pair("TPE3", "CONDUCTOR"),
-    std::pair("TPE4", "REMIXER"),     // could also be ARRANGER
-    std::pair("TPOS", "DISCNUMBER"),
-    std::pair("TPRO", "PRODUCEDNOTICE"),
-    std::pair("TPUB", "LABEL"),
-    std::pair("TRCK", "TRACKNUMBER"),
-    std::pair("TRSN", "RADIOSTATION"),
-    std::pair("TRSO", "RADIOSTATIONOWNER"),
-    std::pair("TSOA", "ALBUMSORT"),
-    std::pair("TSOC", "COMPOSERSORT"),
-    std::pair("TSOP", "ARTISTSORT"),
-    std::pair("TSOT", "TITLESORT"),
-    std::pair("TSO2", "ALBUMARTISTSORT"), // non-standard, used by iTunes
-    std::pair("TSRC", "ISRC"),
-    std::pair("TSSE", "ENCODING"),
-    std::pair("TSST", "DISCSUBTITLE"),
-    // URL frames
-    std::pair("WCOP", "COPYRIGHTURL"),
-    std::pair("WOAF", "FILEWEBPAGE"),
-    std::pair("WOAR", "ARTISTWEBPAGE"),
-    std::pair("WOAS", "AUDIOSOURCEWEBPAGE"),
-    std::pair("WORS", "RADIOSTATIONWEBPAGE"),
-    std::pair("WPAY", "PAYMENTWEBPAGE"),
-    std::pair("WPUB", "PUBLISHERWEBPAGE"),
-    // std::pair("WXXX", "URL"), handled specially
-    // Other frames
-    std::pair("COMM", "COMMENT"),
-    // std::pair("USLT", "LYRICS"), handled specially
-    // Apple iTunes proprietary frames
-    std::pair("PCST", "PODCAST"),
-    std::pair("TCAT", "PODCASTCATEGORY"),
-    std::pair("TDES", "PODCASTDESC"),
-    std::pair("TGID", "PODCASTID"),
-    std::pair("WFED", "PODCASTURL"),
-    std::pair("MVNM", "MOVEMENTNAME"),
-    std::pair("MVIN", "MOVEMENTNUMBER"),
-    std::pair("GRP1", "GROUPING"),
-    std::pair("TCMP", "COMPILATION"),
-  };
-
-  constexpr std::array txxxFrameTranslation {
-    std::pair("MUSICBRAINZ ALBUM ID", "MUSICBRAINZ_ALBUMID"),
-    std::pair("MUSICBRAINZ ARTIST ID", "MUSICBRAINZ_ARTISTID"),
-    std::pair("MUSICBRAINZ ALBUM ARTIST ID", "MUSICBRAINZ_ALBUMARTISTID"),
-    std::pair("MUSICBRAINZ ALBUM RELEASE COUNTRY", "RELEASECOUNTRY"),
-    std::pair("MUSICBRAINZ ALBUM STATUS", "RELEASESTATUS"),
-    std::pair("MUSICBRAINZ ALBUM TYPE", "RELEASETYPE"),
-    std::pair("MUSICBRAINZ RELEASE GROUP ID", "MUSICBRAINZ_RELEASEGROUPID"),
-    std::pair("MUSICBRAINZ RELEASE TRACK ID", "MUSICBRAINZ_RELEASETRACKID"),
-    std::pair("MUSICBRAINZ WORK ID", "MUSICBRAINZ_WORKID"),
-    std::pair("ACOUSTID ID", "ACOUSTID_ID"),
-    std::pair("ACOUSTID FINGERPRINT", "ACOUSTID_FINGERPRINT"),
-    std::pair("MUSICIP PUID", "MUSICIP_PUID"),
-  };
-
-  // list of deprecated frames and their successors
-  constexpr std::array deprecatedFrames {
-    std::pair("TRDA", "TDRC"), // 2.3 -> 2.4 (http://en.wikipedia.org/wiki/ID3)
-    std::pair("TDAT", "TDRC"), // 2.3 -> 2.4
-    std::pair("TYER", "TDRC"), // 2.3 -> 2.4
-    std::pair("TIME", "TDRC"), // 2.3 -> 2.4
-  };
-}  // namespace
-
-String Frame::frameIDToKey(const ByteVector &id)
-{
-  ByteVector id24 = id;
-  for(const auto &[o, t] : deprecatedFrames) {
-    if(id24 == o) {
-      id24 = t;
-      break;
-    }
-  }
-  for(const auto &[o, t] : frameTranslation) {
-    if(id24 == o)
-      return t;
-  }
-  return String();
-}
-
-ByteVector Frame::keyToFrameID(const String &s)
-{
-  const String key = s.upper();
-  for(const auto &[o, t] : frameTranslation) {
-    if(key == t)
-      return o;
-  }
-  return ByteVector();
-}
-
-String Frame::txxxToKey(const String &description)
-{
-  const String d = description.upper();
-  for(const auto &[o, t] : txxxFrameTranslation) {
-    if(d == o)
-      return t;
-  }
-  return d;
-}
-
-String Frame::keyToTXXX(const String &s)
-{
-  const String key = s.upper();
-  for(const auto &[o, t] : txxxFrameTranslation) {
-    if(key == t)
-      return o;
-  }
-  return s;
-}
-
 PropertyMap Frame::asProperties() const
 {
  if(dynamic_cast< const UnknownFrame *>(this)) {
--- a/taglib/mpeg/id3v2/id3v2frame.h
+++ b/taglib/mpeg/id3v2/id3v2frame.h
@@ -54,18 +54,9 @@ namespace TagLib {
    class TAGLIB_EXPORT Frame
    {
      friend class Tag;
-      friend class FrameFactory;
-      friend class TableOfContentsFrame;
-      friend class ChapterFrame;

    public:
-
-      /*!
-       * Creates a textual frame which corresponds to a single key in the PropertyMap
-       * interface. These are all (User)TextIdentificationFrames except TIPL and TMCL,
-       * all (User)URLLinkFrames, CommentsFrames, and UnsynchronizedLyricsFrame.
-       */
-      static Frame *createTextualFrame(const String &key, const StringList &values);
+      class Header;

      /*!
       * Destroys this Frame instance.
@@ -122,12 +113,29 @@ namespace TagLib {
       */
      ByteVector render() const;

+      /*!
+       * Returns a pointer to the frame header.
+       */
+      Header *header() const;
+
      /*!
       * Returns the text delimiter that is used between fields for the string
       * type \a t.
       */
      static ByteVector textDelimiter(String::Type t);

+      /*!
+       * Returns an appropriate ID3 frame ID for the given free-form tag key. This method
+       * will return an empty ByteVector if no specialized translation is found.
+       */
+      static ByteVector keyToFrameID(const String &);
+
+      /*!
+       * Returns a free-form tag name for the given ID3 frame ID. Note that this does not work
+       * for general frame IDs such as TXXX or WXXX; in such a case an empty string is returned.
+       */
+      static String frameIDToKey(const ByteVector &);
+
      /*!
       * The string with which an instrument name is prefixed to build a key in a PropertyMap;
       * used to translate PropertyMaps to TMCL frames. In the current implementation, this
@@ -151,8 +159,6 @@ namespace TagLib {
      static const String urlPrefix;

    protected:
-      class Header;
-
      /*!
       * Constructs an ID3v2 frame using \a data to read the header information.
       * All other processing of \a data should be handled in a subclass.
@@ -170,11 +176,6 @@ namespace TagLib {
       */
      Frame(Header *h);

-      /*!
-       * Returns a pointer to the frame header.
-       */
-      Header *header() const;
-
      /*!
       * Sets the header to \a h.  If \a deleteCurrent is true, this will free
       * the memory of the current header.
@@ -236,28 +237,6 @@ namespace TagLib {
       */
      virtual PropertyMap asProperties() const;

-      /*!
-       * Returns an appropriate ID3 frame ID for the given free-form tag key. This method
-       * will return an empty ByteVector if no specialized translation is found.
-       */
-      static ByteVector keyToFrameID(const String &);
-
-      /*!
-       * Returns a free-form tag name for the given ID3 frame ID. Note that this does not work
-       * for general frame IDs such as TXXX or WXXX; in such a case an empty string is returned.
-       */
-      static String frameIDToKey(const ByteVector &);
-
-      /*!
-       * Returns an appropriate TXXX frame description for the given free-form tag key.
-       */
-      static String keyToTXXX(const String &);
-
-      /*!
-       * Returns a free-form tag name for the given ID3 frame description.
-       */
-      static String txxxToKey(const String &);
-
      /*!
       * This helper function splits the PropertyMap \a original into three ProperytMaps
       * \a singleFrameProperties, \a tiplProperties, and \a tmclProperties, such that:
--- a/taglib/mpeg/id3v2/id3v2framefactory.cpp
+++ b/taglib/mpeg/id3v2/id3v2framefactory.cpp
@@ -370,6 +370,11 @@ void FrameFactory::setDefaultTextEncoding(String::Type encoding)
  d->defaultEncoding = encoding;
 }

+bool FrameFactory::isUsingDefaultTextEncoding() const
+{
+  return d->useDefaultEncoding;
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 // protected members
 ////////////////////////////////////////////////////////////////////////////////
@@ -538,3 +543,54 @@ bool FrameFactory::updateFrame(Frame::Header *header) const

  return true;
 }
+
+Frame *FrameFactory::createFrameForProperty(const String &key, const StringList &values) const
+{
+  // check if the key is contained in the key<=>frameID mapping
+  ByteVector frameID = Frame::keyToFrameID(key);
+  if(!frameID.isEmpty()) {
+    // Apple proprietary WFED (Podcast URL), MVNM (Movement Name), MVIN (Movement Number), GRP1 (Grouping) are in fact text frames.
+    if(frameID[0] == 'T' || frameID == "WFED" || frameID == "MVNM" || frameID == "MVIN" || frameID == "GRP1"){ // text frame
+      auto frame = new TextIdentificationFrame(frameID, String::UTF8);
+      frame->setText(values);
+      return frame;
+    } if((frameID[0] == 'W') && (values.size() == 1)){  // URL frame (not WXXX); support only one value
+        auto frame = new UrlLinkFrame(frameID);
+        frame->setUrl(values.front());
+        return frame;
+    } if(frameID == "PCST") {
+      return new PodcastFrame();
+    }
+  }
+  if(key == "MUSICBRAINZ_TRACKID" && values.size() == 1) {
+    auto frame = new UniqueFileIdentifierFrame("http://musicbrainz.org", values.front().data(String::UTF8));
+    return frame;
+  }
+  // now we check if it's one of the "special" cases:
+  // -LYRICS: depending on the number of values, use USLT or TXXX (with description=LYRICS)
+  if((key == "LYRICS" || key.startsWith(Frame::lyricsPrefix)) && values.size() == 1){
+    auto frame = new UnsynchronizedLyricsFrame(String::UTF8);
+    frame->setDescription(key == "LYRICS" ? key : key.substr(Frame::lyricsPrefix.size()));
+    frame->setText(values.front());
+    return frame;
+  }
+  // -URL: depending on the number of values, use WXXX or TXXX (with description=URL)
+  if((key == "URL" || key.startsWith(Frame::urlPrefix)) && values.size() == 1){
+    auto frame = new UserUrlLinkFrame(String::UTF8);
+    frame->setDescription(key == "URL" ? key : key.substr(Frame::urlPrefix.size()));
+    frame->setUrl(values.front());
+    return frame;
+  }
+  // -COMMENT: depending on the number of values, use COMM or TXXX (with description=COMMENT)
+  if((key == "COMMENT" || key.startsWith(Frame::commentPrefix)) && values.size() == 1){
+    auto frame = new CommentsFrame(String::UTF8);
+    if (key != "COMMENT"){
+      frame->setDescription(key.substr(Frame::commentPrefix.size()));
+    }
+    frame->setText(values.front());
+    return frame;
+  }
+  // if none of the above cases apply, we use a TXXX frame with the key as description
+  return new UserTextIdentificationFrame(
+    UserTextIdentificationFrame::keyToTXXX(key), values, String::UTF8);
+}
--- a/taglib/mpeg/id3v2/id3v2framefactory.h
+++ b/taglib/mpeg/id3v2/id3v2framefactory.h
@@ -50,10 +50,11 @@ namespace TagLib {
     * factory to be the default factory in ID3v2::Tag constructor you can
     * implement behavior that will allow for new ID3v2::Frame subclasses (also
     * provided by you) to be used.
+     * See \c testFrameFactory() in \e tests/test_mpeg.cpp for an example.
     *
     * This implements both <i>abstract factory</i> and <i>singleton</i> patterns
     * of which more information is available on the web and in software design
-     * textbooks (Notably <i>Design Patters</i>).
+     * textbooks (Notably <i>Design Patterns</i>).
     *
     * \note You do not need to use this factory to create new frames to add to
     * an ID3v2::Tag.  You can instantiate frame subclasses directly (with new)
@@ -76,6 +77,14 @@ namespace TagLib {
       */
      virtual Frame *createFrame(const ByteVector &data, const Header *tagHeader) const;

+      /*!
+       * Creates a textual frame which corresponds to a single key in the
+       * PropertyMap interface.  TIPL and TMCL do not belong to this category
+       * and are thus handled explicitly in the Frame class.
+       */
+      virtual Frame *createFrameForProperty(
+        const String &key, const StringList &values) const;
+
      /*!
       * After a tag has been read, this tries to rebuild some of them
       * information, most notably the recording date, from frames that
@@ -105,6 +114,18 @@ namespace TagLib {
       */
      void setDefaultTextEncoding(String::Type encoding);

+      /*!
+       * Returns true if defaultTextEncoding() is used.
+       * The default text encoding is used when setDefaultTextEncoding() has
+       * been called.  In this case, reimplementations of FrameFactory should
+       * use defaultTextEncoding() on the frames (having a text encoding field)
+       * they create.
+       *
+       * \see defaultTextEncoding()
+       * \see setDefaultTextEncoding()
+       */
+      bool isUsingDefaultTextEncoding() const;
+
    protected:
      /*!
       * Constructs a frame factory.  Because this is a singleton this method is
--- a/taglib/mpeg/id3v2/id3v2tag.cpp
+++ b/taglib/mpeg/id3v2/id3v2tag.cpp
@@ -443,13 +443,13 @@ PropertyMap ID3v2::Tag::setProperties(const PropertyMap &origProps)
  // now create remaining frames:
  // start with the involved people list (TIPL)
  if(!tiplProperties.isEmpty())
-      addFrame(TextIdentificationFrame::createTIPLFrame(tiplProperties));
+    addFrame(TextIdentificationFrame::createTIPLFrame(tiplProperties));
  // proceed with the musician credit list (TMCL)
  if(!tmclProperties.isEmpty())
-      addFrame(TextIdentificationFrame::createTMCLFrame(tmclProperties));
+    addFrame(TextIdentificationFrame::createTMCLFrame(tmclProperties));
  // now create the "one key per frame" frames
  for(const auto &[tag, frames] : std::as_const(properties))
-      addFrame(Frame::createTextualFrame(tag, frames));
+    addFrame(d->factory->createFrameForProperty(tag, frames));
  return PropertyMap(); // ID3 implements the complete PropertyMap interface, so an empty map is returned
 }