diff --git a/mkvmuxer.cpp b/mkvmuxer.cpp
index b471936..20d9302 100644
--- a/mkvmuxer.cpp
+++ b/mkvmuxer.cpp
@@ -1045,6 +1045,19 @@ bool Cluster::AddFrame(const uint8* frame,
                       &WriteSimpleBlock);
 }
 
+bool Cluster::AddMetadata(const uint8* frame,
+                          uint64 length,
+                          uint64 track_number,
+                          uint64 abs_timecode,
+                          uint64 duration_timecode) {
+  return DoWriteBlock(frame,
+                      length,
+                      track_number,
+                      abs_timecode,
+                      duration_timecode,
+                      &WriteMetadataBlock);
+}
+
 void Cluster::AddPayloadSize(uint64 size) {
   payload_size_ += size;
 }
@@ -1727,6 +1740,49 @@ bool Segment::AddFrame(const uint8* frame,
   return true;
 }
 
+bool Segment::AddMetadata(const uint8* frame,
+                          uint64 length,
+                          uint64 track_number,
+                          uint64 timestamp_ns,
+                          uint64 duration_ns) {
+  if (!frame)
+    return false;
+
+  if (!CheckHeaderInfo())
+    return false;
+
+  // Check for non-monotonically increasing timestamps.
+  if (timestamp_ns < last_timestamp_)
+    return false;
+
+  if (!DoNewClusterProcessing(track_number, timestamp_ns, true))
+    return false;
+
+  if (cluster_list_size_ < 1)
+    return false;
+
+  Cluster* const cluster = cluster_list_[cluster_list_size_-1];
+
+  if (!cluster)
+    return false;
+
+  const uint64 timecode_scale = segment_info_.timecode_scale();
+  const uint64 abs_timecode = timestamp_ns / timecode_scale;
+  const uint64 duration_timecode = duration_ns / timecode_scale;
+
+  if (!cluster->AddMetadata(frame,
+                            length,
+                            track_number,
+                            abs_timecode,
+                            duration_timecode))
+    return false;
+
+  if (timestamp_ns > last_timestamp_)
+    last_timestamp_ = timestamp_ns;
+
+  return true;
+}
+
 void Segment::OutputCues(bool output_cues) {
   output_cues_ = output_cues;
 }
diff --git a/mkvmuxer.hpp b/mkvmuxer.hpp
index 9a25b27..3e9b592 100644
--- a/mkvmuxer.hpp
+++ b/mkvmuxer.hpp
@@ -499,6 +499,26 @@ class Cluster {
                 uint64 timecode,  // timecode units (absolute)
                 bool is_key);
 
+  // Writes a frame of metadata to the output medium; returns true on
+  // success.
+  // Inputs:
+  //   frame: Pointer to the data
+  //   length: Length of the data
+  //   track_number: Track to add the data to. Value returned by Add track
+  //                 functions.  The range of allowed values is [1, 126].
+  //   timecode:     Absolute (not relative to cluster) timestamp of the
+  //                 metadata frame, expressed in timecode units.
+  //   duration:     Duration of metadata frame, in timecode units.
+  //
+  // The metadata frame is written as a block group, with a duration
+  // sub-element but no reference time sub-elements (indicating that
+  // it is considered a keyframe, per Matroska semantics).
+  bool AddMetadata(const uint8* frame,
+                   uint64 length,
+                   uint64 track_number,
+                   uint64 timecode,  // timecode units (absolute)
+                   uint64 duration);  // timecode units
+
   // Increments the size of the cluster's data in bytes.
   void AddPayloadSize(uint64 size);
 
@@ -524,7 +544,7 @@ class Cluster {
                                int64 timecode,
                                uint64 generic_arg);
 
-  //  Used to implement AddFrame.
+  //  Used to implement AddFrame and AddMetadata.
   bool DoWriteBlock(const uint8* frame,
                     uint64 length,
                     uint64 track_number,
@@ -700,6 +720,26 @@ class Segment {
                 uint64 timestamp_ns,
                 bool is_key);
 
+  // Writes a frame of metadata to the output medium; returns true on
+  // success.
+  // Inputs:
+  //   frame: Pointer to the data
+  //   length: Length of the data
+  //   track_number: Track to add the data to. Value returned by Add track
+  //                 functions.
+  //   timecode:     Absolute timestamp of the metadata frame, expressed
+  //                 in nanosecond units.
+  //   duration:     Duration of metadata frame, in nanosecond units.
+  //
+  // The metadata frame is written as a block group, with a duration
+  // sub-element but no reference time sub-elements (indicating that
+  // it is considered a keyframe, per Matroska semantics).
+  bool AddMetadata(const uint8* frame,
+                   uint64 length,
+                   uint64 track_number,
+                   uint64 timestamp_ns,
+                   uint64 duration_ns);
+
   // Adds a video track to the segment. Returns the number of the track on
   // success, 0 on error. |number| is the number to use for the video track.
   // |number| must be >= 0. If |number| == 0 then the muxer will decide on