diff --git a/packager/app/packager_main.cc b/packager/app/packager_main.cc
index ab986b2630..47696ca329 100644
--- a/packager/app/packager_main.cc
+++ b/packager/app/packager_main.cc
@@ -19,6 +19,7 @@
 #include "packager/base/logging.h"
 #include "packager/base/stl_util.h"
 #include "packager/base/strings/string_split.h"
+#include "packager/base/strings/string_util.h"
 #include "packager/base/strings/stringprintf.h"
 #include "packager/base/threading/simple_thread.h"
 #include "packager/base/time/clock.h"
@@ -31,6 +32,7 @@
 #include "packager/media/event/vod_media_info_dump_muxer_listener.h"
 #include "packager/media/file/file.h"
 #include "packager/media/formats/mp4/mp4_muxer.h"
+#include "packager/media/formats/webm/webm_muxer.h"
 #include "packager/mpd/base/dash_iop_mpd_notifier.h"
 #include "packager/mpd/base/media_info.pb.h"
 #include "packager/mpd/base/mpd_builder.h"
@@ -181,6 +183,25 @@ bool StreamInfoToTextMediaInfo(const StreamDescriptor& stream_descriptor,
   return true;
 }
 
+scoped_ptr<Muxer> CreateOutputMuxer(const MuxerOptions& options) {
+  // TODO(modmaker): Add a config option for output format
+  const std::string& file_name = options.output_file_name;
+  if (base::EndsWith(file_name, ".webm",
+                     base::CompareCase::INSENSITIVE_ASCII)) {
+    return scoped_ptr<Muxer>(new webm::WebMMuxer(options));
+  } else if (base::EndsWith(file_name, ".mp4",
+                            base::CompareCase::INSENSITIVE_ASCII) ||
+             base::EndsWith(file_name, ".m4a",
+                            base::CompareCase::INSENSITIVE_ASCII) ||
+             base::EndsWith(file_name, ".m4v",
+                            base::CompareCase::INSENSITIVE_ASCII)) {
+    return scoped_ptr<Muxer>(new mp4::MP4Muxer(options));
+  } else {
+    LOG(ERROR) << "Unrecognized output format " << file_name;
+    return NULL;
+  }
+}
+
 bool CreateRemuxJobs(const StreamDescriptorList& stream_descriptors,
                      const MuxerOptions& muxer_options,
                      FakeClock* fake_clock,
@@ -261,7 +282,9 @@ bool CreateRemuxJobs(const StreamDescriptorList& stream_descriptors,
     }
     DCHECK(!remux_jobs->empty());
 
-    scoped_ptr<Muxer> muxer(new mp4::MP4Muxer(stream_muxer_options));
+    scoped_ptr<Muxer> muxer(CreateOutputMuxer(stream_muxer_options));
+    if (!muxer)
+      return false;
     if (FLAGS_use_fake_clock_for_muxer) muxer->set_clock(fake_clock);
 
     if (key_source) {
diff --git a/packager/media/file/file.cc b/packager/media/file/file.cc
index f495e70ec1..a2929de0c3 100644
--- a/packager/media/file/file.cc
+++ b/packager/media/file/file.cc
@@ -6,6 +6,8 @@
 
 #include "packager/media/file/file.h"
 
+#include <algorithm>
+
 #include <gflags/gflags.h>
 #include "packager/base/logging.h"
 #include "packager/base/memory/scoped_ptr.h"
@@ -205,5 +207,43 @@ bool File::Copy(const char* from_file_name, const char* to_file_name) {
   return true;
 }
 
+int64_t File::CopyFile(File* source, File* destination) {
+  return CopyFile(source, destination, kWholeFile);
+}
+
+int64_t File::CopyFile(File* source, File* destination, int64_t max_copy) {
+  DCHECK(source);
+  DCHECK(destination);
+  if (max_copy < 0)
+    max_copy = std::numeric_limits<int64_t>::max();
+
+  const int64_t kBufferSize = 0x40000;  // 256KB.
+  scoped_ptr<uint8_t[]> buffer(new uint8_t[kBufferSize]);
+  int64_t bytes_copied = 0;
+  while (bytes_copied < max_copy) {
+    const int64_t size = std::min(kBufferSize, max_copy - bytes_copied);
+    const int64_t bytes_read = source->Read(buffer.get(), size);
+    if (bytes_read < 0)
+      return bytes_read;
+    if (bytes_read == 0)
+      break;
+
+    int64_t total_bytes_written = 0;
+    while (total_bytes_written < bytes_read) {
+      const int64_t bytes_written = destination->Write(
+          buffer.get() + total_bytes_written, bytes_read - total_bytes_written);
+      if (bytes_written < 0)
+        return bytes_written;
+
+      total_bytes_written += bytes_written;
+    }
+
+    DCHECK_EQ(total_bytes_written, bytes_read);
+    bytes_copied += bytes_read;
+  }
+
+  return bytes_copied;
+}
+
 }  // namespace media
 }  // namespace edash_packager
diff --git a/packager/media/file/file.h b/packager/media/file/file.h
index 9c4489061b..f1a54d035b 100644
--- a/packager/media/file/file.h
+++ b/packager/media/file/file.h
@@ -17,6 +17,7 @@ namespace edash_packager {
 namespace media {
 
 extern const char* kLocalFilePrefix;
+const int64_t kWholeFile = -1;
 
 /// Define an abstract file interface.
 class File {
@@ -110,6 +111,19 @@ class File {
   /// @return true on success, false otherwise.
   static bool Copy(const char* from_file_name, const char* to_file_name);
 
+  /// Copies the contents from source to destination.
+  /// @param source The file to copy from.
+  /// @param destination The file to copy to.
+  /// @return Number of bytes written, or a value < 0 on error.
+  static int64_t CopyFile(File* source, File* destination);
+
+  /// Copies the contents from source to destination.
+  /// @param source The file to copy from.
+  /// @param destination The file to copy to.
+  /// @param max_copy The maximum number of bytes to copy; < 0 to copy to EOF.
+  /// @return Number of bytes written, or a value < 0 on error.
+  static int64_t CopyFile(File* source, File* destination, int64_t max_copy);
+
  protected:
   explicit File(const std::string& file_name) : file_name_(file_name) {}
   /// Do *not* call the destructor directly (with the "delete" keyword)
diff --git a/packager/media/formats/webm/mkv_writer.cc b/packager/media/formats/webm/mkv_writer.cc
new file mode 100644
index 0000000000..634c4d5800
--- /dev/null
+++ b/packager/media/formats/webm/mkv_writer.cc
@@ -0,0 +1,86 @@
+// Copyright 2015 Google Inc. All rights reserved.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file or at
+// https://developers.google.com/open-source/licenses/bsd
+
+#include "packager/media/formats/webm/mkv_writer.h"
+
+namespace edash_packager {
+namespace media {
+
+MkvWriter::MkvWriter() : position_(0) {}
+
+MkvWriter::~MkvWriter() {}
+
+Status MkvWriter::Open(const std::string& name) {
+  DCHECK(!file_);
+  file_.reset(File::Open(name.c_str(), "w"));
+  if (!file_)
+    return Status(error::FILE_FAILURE, "Unable to open file for writing.");
+
+  // This may produce an error message; however there isn't a seekable method
+  // on File.
+  seekable_ = file_->Seek(0);
+  position_ = 0;
+  return Status::OK;
+}
+
+mkvmuxer::int32 MkvWriter::Write(const void* buf, mkvmuxer::uint32 len) {
+  DCHECK(file_);
+
+  const char* data = reinterpret_cast<const char*>(buf);
+  int64_t total_bytes_written = 0;
+  while (total_bytes_written < len) {
+    const int64_t written =
+        file_->Write(data + total_bytes_written, len - total_bytes_written);
+    if (written < 0)
+      return written;
+
+    total_bytes_written += written;
+  }
+
+  DCHECK_EQ(total_bytes_written, len);
+  position_ += len;
+  return 0;
+}
+
+int64_t MkvWriter::WriteFromFile(File* source) {
+  return WriteFromFile(source, kWholeFile);
+}
+
+int64_t MkvWriter::WriteFromFile(File* source, uint64_t max_copy) {
+  DCHECK(file_);
+
+  const int64_t size = File::CopyFile(source, file_.get(), max_copy);
+  if (size < 0)
+    return size;
+
+  position_ += size;
+  return size;
+}
+
+mkvmuxer::int64 MkvWriter::Position() const {
+  return position_;
+}
+
+mkvmuxer::int32 MkvWriter::Position(mkvmuxer::int64 position) {
+  DCHECK(file_);
+
+  if (file_->Seek(position)) {
+    position_ = position;
+    return 0;
+  } else {
+    return -1;
+  }
+}
+
+bool MkvWriter::Seekable() const {
+  return seekable_;
+}
+
+void MkvWriter::ElementStartNotify(mkvmuxer::uint64 element_id,
+                                   mkvmuxer::int64 position) {}
+
+}  // namespace media
+}  // namespace edash_packager
diff --git a/packager/media/formats/webm/mkv_writer.h b/packager/media/formats/webm/mkv_writer.h
new file mode 100644
index 0000000000..8705a3cc59
--- /dev/null
+++ b/packager/media/formats/webm/mkv_writer.h
@@ -0,0 +1,73 @@
+// Copyright 2015 Google Inc. All rights reserved.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file or at
+// https://developers.google.com/open-source/licenses/bsd
+
+#ifndef MEDIA_FORMATS_WEBM_MKV_WRITER_H_
+#define MEDIA_FORMATS_WEBM_MKV_WRITER_H_
+
+#include <string>
+
+#include "packager/base/memory/scoped_ptr.h"
+#include "packager/media/base/status.h"
+#include "packager/media/file/file_closer.h"
+#include "packager/third_party/libwebm/src/mkvmuxer.hpp"
+
+namespace edash_packager {
+namespace media {
+
+/// An implementation of IMkvWriter using our File type.
+class MkvWriter : public mkvmuxer::IMkvWriter {
+ public:
+  MkvWriter();
+  ~MkvWriter() override;
+
+  /// Opens the given file for writing.  This MUST be called before any other
+  /// calls.
+  /// @param name The path to the file to open.
+  /// @return Whether the operation succeeded.
+  Status Open(const std::string& name);
+
+  /// Writes out @a len bytes of @a buf.
+  /// @return 0 on success.
+  mkvmuxer::int32 Write(const void* buf, mkvmuxer::uint32 len) override;
+  /// @return The offset of the output position from the beginning of the
+  ///         output.
+  mkvmuxer::int64 Position() const override;
+  /// Set the current File position.
+  /// @return 0 on success.
+  mkvmuxer::int32 Position(mkvmuxer::int64 position) override;
+  /// @return true if the writer is seekable.
+  bool Seekable() const override;
+  /// Element start notification. Called whenever an element identifier is about
+  /// to be written to the stream.  @a element_id is the element identifier, and
+  /// @a position is the location in the WebM stream where the first octet of
+  /// the element identifier will be written.
+  /// Note: the |MkvId| enumeration in webmids.hpp defines element values.
+  void ElementStartNotify(mkvmuxer::uint64 element_id,
+                          mkvmuxer::int64 position) override;
+
+  /// Writes the contents of the given file to this file.
+  /// @return The number of bytes written; or < 0 on error.
+  int64_t WriteFromFile(File* source);
+  /// Writes the contents of the given file to this file, up to a maximum
+  /// number of bytes.  If @a max_copy is negative, will copy to EOF.
+  /// @return The number of bytes written; or < 0 on error.
+  int64_t WriteFromFile(File* source, uint64_t max_copy);
+
+  File* file() { return file_.get(); }
+
+ private:
+  scoped_ptr<File, FileCloser> file_;
+  // Keep track of the position and whether we can seek.
+  mkvmuxer::int64 position_;
+  bool seekable_;
+
+  DISALLOW_COPY_AND_ASSIGN(MkvWriter);
+};
+
+}  // namespace media
+}  // namespace edash_packager
+
+#endif  // MEDIA_FORMATS_WEBM_MKV_WRITER_H_
diff --git a/packager/media/formats/webm/multi_segment_segmenter.cc b/packager/media/formats/webm/multi_segment_segmenter.cc
new file mode 100644
index 0000000000..4f6da88146
--- /dev/null
+++ b/packager/media/formats/webm/multi_segment_segmenter.cc
@@ -0,0 +1,91 @@
+// Copyright 2015 Google Inc. All rights reserved.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file or at
+// https://developers.google.com/open-source/licenses/bsd
+
+#include "packager/media/formats/webm/multi_segment_segmenter.h"
+
+#include "packager/media/base/media_stream.h"
+#include "packager/media/base/muxer_options.h"
+#include "packager/media/base/muxer_util.h"
+#include "packager/media/base/stream_info.h"
+#include "packager/media/event/muxer_listener.h"
+#include "packager/third_party/libwebm/src/mkvmuxer.hpp"
+
+namespace edash_packager {
+namespace media {
+namespace webm {
+MultiSegmentSegmenter::MultiSegmentSegmenter(const MuxerOptions& options)
+    : Segmenter(options), num_segment_(0) {}
+
+MultiSegmentSegmenter::~MultiSegmentSegmenter() {}
+
+bool MultiSegmentSegmenter::GetInitRangeStartAndEnd(uint32_t* start,
+                                                    uint32_t* end) {
+  return false;
+}
+
+bool MultiSegmentSegmenter::GetIndexRangeStartAndEnd(uint32_t* start,
+                                                     uint32_t* end) {
+  return false;
+}
+
+Status MultiSegmentSegmenter::DoInitialize(scoped_ptr<MkvWriter> writer) {
+  writer_ = writer.Pass();
+  return WriteSegmentHeader(0, writer_.get());
+}
+
+Status MultiSegmentSegmenter::DoFinalize() {
+  return FinalizeSegment();
+}
+
+Status MultiSegmentSegmenter::FinalizeSegment() {
+  if (!cluster()->Finalize())
+    return Status(error::FILE_FAILURE, "Error finalizing segment.");
+
+  if (muxer_listener()) {
+    const uint64_t size = cluster()->Size();
+    const uint64_t start_webm_timecode = cluster()->timecode();
+    const uint64_t start_timescale = FromWebMTimecode(start_webm_timecode);
+    const uint64_t length = static_cast<uint64_t>(
+        cluster_length_sec() * stream()->info()->time_scale());
+    muxer_listener()->OnNewSegment(start_timescale, length, size);
+  }
+
+  VLOG(1) << "WEBM file '" << writer_->file()->file_name() << "' finalized.";
+  return Status::OK;
+}
+
+Status MultiSegmentSegmenter::NewSubsegment(uint64_t start_timescale) {
+  if (cluster() && !cluster()->Finalize())
+    return Status(error::FILE_FAILURE, "Error finalizing segment.");
+
+  uint64_t start_webm_timecode = FromBMFFTimescale(start_timescale);
+  return SetCluster(start_webm_timecode, 0, writer_.get());
+}
+
+Status MultiSegmentSegmenter::NewSegment(uint64_t start_timescale) {
+  if (cluster()) {
+    Status temp = FinalizeSegment();
+    if (!temp.ok())
+      return temp;
+  }
+
+  // Create a new file for the new segment.
+  std::string segment_name =
+      GetSegmentName(options().segment_template, start_timescale, num_segment_,
+                     options().bandwidth);
+  writer_.reset(new MkvWriter);
+  Status status = writer_->Open(segment_name);
+  if (!status.ok())
+    return status;
+  num_segment_++;
+
+  uint64_t start_webm_timecode = FromBMFFTimescale(start_timescale);
+  return SetCluster(start_webm_timecode, 0, writer_.get());
+}
+
+}  // namespace webm
+}  // namespace media
+}  // namespace edash_packager
diff --git a/packager/media/formats/webm/multi_segment_segmenter.h b/packager/media/formats/webm/multi_segment_segmenter.h
new file mode 100644
index 0000000000..74015630ab
--- /dev/null
+++ b/packager/media/formats/webm/multi_segment_segmenter.h
@@ -0,0 +1,58 @@
+// Copyright 2015 Google Inc. All rights reserved.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file or at
+// https://developers.google.com/open-source/licenses/bsd
+
+#ifndef MEDIA_FORMATS_WEBM_MULTI_SEGMENT_SEGMENTER_H_
+#define MEDIA_FORMATS_WEBM_MULTI_SEGMENT_SEGMENTER_H_
+
+#include "packager/media/formats/webm/segmenter.h"
+
+#include "packager/base/memory/scoped_ptr.h"
+#include "packager/media/base/status.h"
+#include "packager/media/formats/webm/mkv_writer.h"
+
+namespace edash_packager {
+namespace media {
+
+struct MuxerOptions;
+
+namespace webm {
+
+/// An implementation of a Segmenter for a multi-segment.  Since this does not
+/// use seeking, it does not matter if the underlying files support seeking.
+class MultiSegmentSegmenter : public Segmenter {
+ public:
+  explicit MultiSegmentSegmenter(const MuxerOptions& options);
+  ~MultiSegmentSegmenter() override;
+
+  /// @name Segmenter implementation overrides.
+  /// @{
+  bool GetInitRangeStartAndEnd(uint32_t* start, uint32_t* end) override;
+  bool GetIndexRangeStartAndEnd(uint32_t* start, uint32_t* end) override;
+  /// @}
+
+ protected:
+  // Segmenter implementation overrides.
+  Status DoInitialize(scoped_ptr<MkvWriter> writer) override;
+  Status DoFinalize() override;
+
+ private:
+  // Segmenter implementation overrides.
+  Status NewSubsegment(uint64_t start_timescale) override;
+  Status NewSegment(uint64_t start_timescale) override;
+
+  Status FinalizeSegment();
+
+  scoped_ptr<MkvWriter> writer_;
+  uint32_t num_segment_;
+
+  DISALLOW_COPY_AND_ASSIGN(MultiSegmentSegmenter);
+};
+
+}  // namespace webm
+}  // namespace media
+}  // namespace edash_packager
+
+#endif  // MEDIA_FORMATS_WEBM_MULTI_SEGMENT_SEGMENTER_H_
diff --git a/packager/media/formats/webm/seek_head.cc b/packager/media/formats/webm/seek_head.cc
new file mode 100644
index 0000000000..60a3ca6792
--- /dev/null
+++ b/packager/media/formats/webm/seek_head.cc
@@ -0,0 +1,123 @@
+// Copyright 2015 Google Inc. All rights reserved.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file or at
+// https://developers.google.com/open-source/licenses/bsd
+
+#include "packager/media/formats/webm/seek_head.h"
+
+#include <limits>
+
+#include "packager/third_party/libwebm/src/mkvmuxerutil.hpp"
+#include "packager/third_party/libwebm/src/webmids.hpp"
+
+namespace edash_packager {
+namespace media {
+namespace {
+const mkvmuxer::uint64 kElementIds[] = {mkvmuxer::kMkvCluster,
+                                        mkvmuxer::kMkvCues, mkvmuxer::kMkvInfo,
+                                        mkvmuxer::kMkvTracks};
+const int kElementIdCount = arraysize(kElementIds);
+
+uint64_t MaxSeekEntrySize() {
+  const uint64_t max_entry_payload_size =
+      EbmlElementSize(
+          mkvmuxer::kMkvSeekID,
+          static_cast<mkvmuxer::uint64>(std::numeric_limits<uint32_t>::max())) +
+      EbmlElementSize(mkvmuxer::kMkvSeekPosition,
+                      std::numeric_limits<mkvmuxer::uint64>::max());
+  const uint64_t max_entry_size =
+      EbmlMasterElementSize(mkvmuxer::kMkvSeek, max_entry_payload_size) +
+      max_entry_payload_size;
+
+  return max_entry_size;
+}
+}  // namespace
+
+SeekHead::SeekHead()
+    : cluster_pos_(-1),
+      cues_pos_(-1),
+      info_pos_(-1),
+      tracks_pos_(-1),
+      wrote_void_(false) {}
+
+SeekHead::~SeekHead() {}
+
+bool SeekHead::Write(mkvmuxer::IMkvWriter* writer) {
+  std::vector<uint64_t> element_sizes;
+  const uint64_t payload_size = GetPayloadSize(&element_sizes);
+
+  if (payload_size == 0) {
+    return true;
+  }
+
+  const int64_t start_pos = writer->Position();
+  if (!WriteEbmlMasterElement(writer, mkvmuxer::kMkvSeekHead, payload_size))
+    return false;
+
+  const int64_t positions[] = {cluster_pos_, cues_pos_, info_pos_, tracks_pos_};
+  for (int i = 0; i < kElementIdCount; ++i) {
+    if (element_sizes[i] == 0)
+      continue;
+
+    const mkvmuxer::uint64 position =
+        static_cast<mkvmuxer::uint64>(positions[i]);
+    if (!WriteEbmlMasterElement(writer, mkvmuxer::kMkvSeek, element_sizes[i]) ||
+        !WriteEbmlElement(writer, mkvmuxer::kMkvSeekID, kElementIds[i]) ||
+        !WriteEbmlElement(writer, mkvmuxer::kMkvSeekPosition, position))
+      return false;
+  }
+
+  // If we wrote void before, then fill in the extra with void.
+  if (wrote_void_) {
+    const uint64_t max_payload_size = kElementIdCount * MaxSeekEntrySize();
+    const uint64_t total_void_size =
+        EbmlMasterElementSize(mkvmuxer::kMkvSeekHead, max_payload_size) +
+        max_payload_size;
+
+    const uint64_t extra_void =
+        total_void_size - (writer->Position() - start_pos);
+    if (!WriteVoidElement(writer, extra_void))
+      return false;
+  }
+
+  return true;
+}
+
+bool SeekHead::WriteVoid(mkvmuxer::IMkvWriter* writer) {
+  const uint64_t payload_size = kElementIdCount * MaxSeekEntrySize();
+  const uint64_t total_size =
+      EbmlMasterElementSize(mkvmuxer::kMkvSeekHead, payload_size) +
+      payload_size;
+
+  wrote_void_ = true;
+  const uint64_t written = WriteVoidElement(writer, total_size);
+  if (!written)
+    return false;
+
+  return true;
+}
+
+uint64_t SeekHead::GetPayloadSize(std::vector<uint64_t>* data) {
+  const int64_t positions[] = {cluster_pos_, cues_pos_, info_pos_, tracks_pos_};
+  uint64_t total_payload_size = 0;
+  data->resize(kElementIdCount);
+  for (int i = 0; i < kElementIdCount; ++i) {
+    if (positions[i] < 0) {
+      (*data)[i] = 0;
+      continue;
+    }
+
+    const mkvmuxer::uint64 position =
+        static_cast<mkvmuxer::uint64>(positions[i]);
+    (*data)[i] = EbmlElementSize(mkvmuxer::kMkvSeekID, kElementIds[i]) +
+                 EbmlElementSize(mkvmuxer::kMkvSeekPosition, position);
+    total_payload_size +=
+        data->at(i) + EbmlMasterElementSize(mkvmuxer::kMkvSeek, data->at(i));
+  }
+
+  return total_payload_size;
+}
+
+}  // namespace media
+}  // namespace edash_packager
diff --git a/packager/media/formats/webm/seek_head.h b/packager/media/formats/webm/seek_head.h
new file mode 100644
index 0000000000..438f4b0aac
--- /dev/null
+++ b/packager/media/formats/webm/seek_head.h
@@ -0,0 +1,52 @@
+// Copyright 2015 Google Inc. All rights reserved.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file or at
+// https://developers.google.com/open-source/licenses/bsd
+
+#ifndef MEDIA_FORMATS_WEBM_SEEK_HEAD_H_
+#define MEDIA_FORMATS_WEBM_SEEK_HEAD_H_
+
+#include <stdint.h>
+#include <vector>
+
+#include "base/macros.h"
+#include "packager/third_party/libwebm/src/mkvmuxer.hpp"
+
+namespace edash_packager {
+namespace media {
+
+/// Used to write the SeekHead to the output stream.  This supports non-seekable
+/// files and setting the values before write; this also supports updating.
+class SeekHead {
+ public:
+  SeekHead();
+  ~SeekHead();
+
+  /// Writes the seek head to the given writer.  This should only be called
+  /// once.  For seekable files, use WriteVoid first, then call this method.
+  bool Write(mkvmuxer::IMkvWriter* writer);
+  /// Writes a void element large enough to fit the SeekHead.
+  bool WriteVoid(mkvmuxer::IMkvWriter* writer);
+
+  void set_cluster_pos(uint64_t pos) { cluster_pos_ = pos; }
+  void set_cues_pos(uint64_t pos) { cues_pos_ = pos; }
+  void set_info_pos(uint64_t pos) { info_pos_ = pos; }
+  void set_tracks_pos(uint64_t pos) { tracks_pos_ = pos; }
+
+ private:
+  uint64_t GetPayloadSize(std::vector<uint64_t>* data);
+
+  int64_t cluster_pos_;
+  int64_t cues_pos_;
+  int64_t info_pos_;
+  int64_t tracks_pos_;
+  bool wrote_void_;
+
+  DISALLOW_COPY_AND_ASSIGN(SeekHead);
+};
+
+}  // namespace media
+}  // namespace edash_packager
+
+#endif  // MEDIA_FORMATS_WEBM_SEEK_HEAD_H_
diff --git a/packager/media/formats/webm/segmenter.cc b/packager/media/formats/webm/segmenter.cc
new file mode 100644
index 0000000000..b781168699
--- /dev/null
+++ b/packager/media/formats/webm/segmenter.cc
@@ -0,0 +1,275 @@
+// Copyright 2015 Google Inc. All rights reserved.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file or at
+// https://developers.google.com/open-source/licenses/bsd
+
+#include "packager/media/formats/webm/segmenter.h"
+
+#include "packager/base/time/time.h"
+#include "packager/media/base/audio_stream_info.h"
+#include "packager/media/base/media_sample.h"
+#include "packager/media/base/media_stream.h"
+#include "packager/media/base/muxer_options.h"
+#include "packager/media/base/stream_info.h"
+#include "packager/media/base/video_stream_info.h"
+#include "packager/media/event/muxer_listener.h"
+#include "packager/media/event/progress_listener.h"
+#include "packager/third_party/libwebm/src/mkvmuxerutil.hpp"
+#include "packager/third_party/libwebm/src/webmids.hpp"
+
+namespace edash_packager {
+namespace media {
+namespace webm {
+namespace {
+int64_t kTimecodeScale = 1000000;
+int64_t kSecondsToNs = 1000000000L;
+}  // namespace
+
+Segmenter::Segmenter(const MuxerOptions& options)
+    : options_(options),
+      stream_(NULL),
+      muxer_listener_(NULL),
+      progress_listener_(NULL),
+      progress_target_(0),
+      accumulated_progress_(0),
+      total_duration_(0),
+      sample_duration_(0),
+      segment_payload_pos_(0),
+      cluster_length_sec_(0),
+      segment_length_sec_(0),
+      track_id_(0) {}
+
+Segmenter::~Segmenter() {}
+
+Status Segmenter::Initialize(scoped_ptr<MkvWriter> writer,
+                             MediaStream* streams,
+                             ProgressListener* progress_listener,
+                             MuxerListener* muxer_listener,
+                             KeySource* encryption_key_source) {
+  muxer_listener_ = muxer_listener;
+  stream_ = streams;
+
+  // Use media duration as progress target.
+  progress_target_ = stream_->info()->duration();
+  progress_listener_ = progress_listener;
+
+  segment_info_.Init();
+  segment_info_.set_timecode_scale(kTimecodeScale);
+  if (options().single_segment) {
+    // Set an initial duration so the duration element is written; will be
+    // overwritten at the end.
+    segment_info_.set_duration(1);
+  }
+
+  // Create the track info.
+  Status status;
+  switch (stream_->info()->stream_type()) {
+    case kStreamVideo:
+      status = CreateVideoTrack(
+          static_cast<VideoStreamInfo*>(stream_->info().get()));
+      break;
+    case kStreamAudio:
+      status = CreateAudioTrack(
+          static_cast<AudioStreamInfo*>(stream_->info().get()));
+      break;
+    default:
+      NOTIMPLEMENTED() << "Not implemented for stream type: "
+                       << stream_->info()->stream_type();
+      status = Status(error::UNIMPLEMENTED, "Not implemented for stream type");
+  }
+  if (!status.ok())
+    return status;
+
+  return DoInitialize(writer.Pass());
+}
+
+Status Segmenter::Finalize() {
+  segment_info_.set_duration(FromBMFFTimescale(total_duration_));
+  return DoFinalize();
+}
+
+Status Segmenter::AddSample(scoped_refptr<MediaSample> sample) {
+  if (sample_duration_ == 0) {
+    sample_duration_ = sample->duration();
+    if (muxer_listener_)
+      muxer_listener_->OnSampleDurationReady(sample_duration_);
+  }
+
+  UpdateProgress(sample->duration());
+
+  // Create a new cluster if needed.
+  Status status;
+  if (!cluster_) {
+    status = NewSegment(sample->pts());
+  } else if (segment_length_sec_ >= options_.segment_duration) {
+    if (sample->is_key_frame() || !options_.segment_sap_aligned) {
+      status = NewSegment(sample->pts());
+      segment_length_sec_ = 0;
+      cluster_length_sec_ = 0;
+    }
+  } else if (cluster_length_sec_ >= options_.fragment_duration) {
+    if (sample->is_key_frame() || !options_.fragment_sap_aligned) {
+      status = NewSubsegment(sample->pts());
+      cluster_length_sec_ = 0;
+    }
+  }
+  if (!status.ok())
+    return status;
+
+  const int64_t time_ns =
+      sample->pts() * kSecondsToNs / stream_->info()->time_scale();
+  if (!cluster_->AddFrame(sample->data(), sample->data_size(), track_id_,
+                          time_ns, sample->is_key_frame())) {
+    LOG(ERROR) << "Error adding sample to segment.";
+    return Status(error::FILE_FAILURE, "Error adding sample to segment.");
+  }
+  const double duration_sec =
+      static_cast<double>(sample->duration()) / stream_->info()->time_scale();
+  cluster_length_sec_ += duration_sec;
+  segment_length_sec_ += duration_sec;
+  total_duration_ += sample->duration();
+
+  return Status::OK;
+}
+
+float Segmenter::GetDuration() const {
+  return static_cast<float>(segment_info_.duration()) *
+         segment_info_.timecode_scale() / kSecondsToNs;
+}
+
+uint64_t Segmenter::FromBMFFTimescale(uint64_t time_timescale) {
+  // Convert the time from BMFF time_code to WebM timecode scale.
+  const int64_t time_ns =
+      kSecondsToNs * time_timescale / stream_->info()->time_scale();
+  return time_ns / segment_info_.timecode_scale();
+}
+
+uint64_t Segmenter::FromWebMTimecode(uint64_t time_webm_timecode) {
+  // Convert the time to BMFF time_code from WebM timecode scale.
+  const int64_t time_ns = time_webm_timecode * segment_info_.timecode_scale();
+  return time_ns * stream_->info()->time_scale() / kSecondsToNs;
+}
+
+Status Segmenter::WriteSegmentHeader(uint64_t file_size, MkvWriter* writer) {
+  Status error_status(error::FILE_FAILURE, "Error writing segment header.");
+
+  if (!WriteEbmlHeader(writer))
+    return error_status;
+
+  if (WriteID(writer, mkvmuxer::kMkvSegment) != 0)
+    return error_status;
+
+  const uint64_t segment_size_size = 8;
+  segment_payload_pos_ = writer->Position() + segment_size_size;
+  if (file_size > 0) {
+    // We want the size of the segment element, so subtract the header.
+    if (WriteUIntSize(writer, file_size - segment_payload_pos_,
+                      segment_size_size) != 0)
+      return error_status;
+    if (!seek_head_.Write(writer))
+      return error_status;
+  } else {
+    if (SerializeInt(writer, mkvmuxer::kEbmlUnknownValue, segment_size_size) !=
+        0)
+      return error_status;
+    // We don't know the header size, so write a placeholder.
+    if (!seek_head_.WriteVoid(writer))
+      return error_status;
+  }
+
+  if (!segment_info_.Write(writer))
+    return error_status;
+
+  if (!tracks_.Write(writer))
+    return error_status;
+
+  return Status::OK;
+}
+
+Status Segmenter::SetCluster(uint64_t start_webm_timecode,
+                             uint64_t position,
+                             MkvWriter* writer) {
+  const uint64_t scale = segment_info_.timecode_scale();
+  cluster_.reset(new mkvmuxer::Cluster(start_webm_timecode, position, scale));
+  cluster_->Init(writer);
+  return Status::OK;
+}
+
+void Segmenter::UpdateProgress(uint64_t progress) {
+  accumulated_progress_ += progress;
+  if (!progress_listener_ || progress_target_ == 0)
+    return;
+  // It might happen that accumulated progress exceeds progress_target due to
+  // computation errors, e.g. rounding error. Cap it so it never reports > 100%
+  // progress.
+  if (accumulated_progress_ >= progress_target_) {
+    progress_listener_->OnProgress(1.0);
+  } else {
+    progress_listener_->OnProgress(static_cast<double>(accumulated_progress_) /
+                                   progress_target_);
+  }
+}
+
+Status Segmenter::CreateVideoTrack(VideoStreamInfo* info) {
+  // The seed is only used to create a UID which we overwrite later.
+  unsigned int seed = 0;
+  mkvmuxer::VideoTrack* track = new mkvmuxer::VideoTrack(&seed);
+  if (!track)
+    return Status(error::INTERNAL_ERROR, "Failed to create video track.");
+
+  if (info->codec() == kCodecVP8) {
+    track->set_codec_id(mkvmuxer::Tracks::kVp8CodecId);
+  } else if (info->codec() == kCodecVP9) {
+    track->set_codec_id(mkvmuxer::Tracks::kVp9CodecId);
+  } else {
+    LOG(ERROR) << "Only VP8 and VP9 video codec is supported.";
+    return Status(error::UNIMPLEMENTED,
+                  "Only VP8 and VP9 video codecs are supported.");
+  }
+
+  track->set_uid(info->track_id());
+  track->set_type(mkvmuxer::Tracks::kVideo);
+  track->set_width(info->width());
+  track->set_height(info->height());
+  track->set_display_height(info->height());
+  track->set_display_width(info->width() * info->pixel_width() /
+                           info->pixel_height());
+  track->set_language(info->language().c_str());
+
+  tracks_.AddTrack(track, info->track_id());
+  track_id_ = track->number();
+  return Status::OK;
+}
+
+Status Segmenter::CreateAudioTrack(AudioStreamInfo* info) {
+  // The seed is only used to create a UID which we overwrite later.
+  unsigned int seed = 0;
+  mkvmuxer::AudioTrack* track = new mkvmuxer::AudioTrack(&seed);
+  if (!track)
+    return Status(error::INTERNAL_ERROR, "Failed to create audio track.");
+
+  if (info->codec() == kCodecOpus) {
+    track->set_codec_id(mkvmuxer::Tracks::kOpusCodecId);
+  } else if (info->codec() == kCodecVorbis) {
+    track->set_codec_id(mkvmuxer::Tracks::kVorbisCodecId);
+  } else {
+    LOG(ERROR) << "Only Vorbis and Opus audio codec is supported.";
+    return Status(error::UNIMPLEMENTED,
+                  "Only Vorbis and Opus audio codecs are supported.");
+  }
+
+  track->set_uid(info->track_id());
+  track->set_language(info->language().c_str());
+  track->set_type(mkvmuxer::Tracks::kAudio);
+  track->set_sample_rate(info->sampling_frequency());
+  track->set_channels(info->num_channels());
+
+  tracks_.AddTrack(track, info->track_id());
+  track_id_ = track->number();
+  return Status::OK;
+}
+
+}  // namespace webm
+}  // namespace media
+}  // namespace edash_packager
diff --git a/packager/media/formats/webm/segmenter.h b/packager/media/formats/webm/segmenter.h
new file mode 100644
index 0000000000..992b52629c
--- /dev/null
+++ b/packager/media/formats/webm/segmenter.h
@@ -0,0 +1,154 @@
+// Copyright 2015 Google Inc. All rights reserved.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file or at
+// https://developers.google.com/open-source/licenses/bsd
+
+#ifndef MEDIA_FORMATS_WEBM_SEGMENTER_H_
+#define MEDIA_FORMATS_WEBM_SEGMENTER_H_
+
+#include "packager/base/memory/ref_counted.h"
+#include "packager/base/memory/scoped_ptr.h"
+#include "packager/media/base/status.h"
+#include "packager/media/formats/webm/mkv_writer.h"
+#include "packager/media/formats/webm/seek_head.h"
+#include "packager/third_party/libwebm/src/mkvmuxer.hpp"
+
+namespace edash_packager {
+namespace media {
+
+struct MuxerOptions;
+
+class AudioStreamInfo;
+class KeySource;
+class MediaSample;
+class MediaStream;
+class MuxerListener;
+class ProgressListener;
+class StreamInfo;
+class VideoStreamInfo;
+
+namespace webm {
+
+class Segmenter {
+ public:
+  explicit Segmenter(const MuxerOptions& options);
+  virtual ~Segmenter();
+
+  /// Initialize the segmenter.
+  /// Calling other public methods of this class without this method returning
+  /// Status::OK results in an undefined behavior.
+  /// @param writer contains the output file (or init file in multi-segment).
+  /// @param streams contains the MediaStream to be segmented.
+  /// @param muxer_listener receives muxer events. Can be NULL.
+  /// @param encryption_key_source points to the key source which contains
+  ///        the encryption keys. It can be NULL to indicate that no encryption
+  ///        is required.
+  /// @return OK on success, an error status otherwise.
+  Status Initialize(scoped_ptr<MkvWriter> writer,
+                    MediaStream* streams,
+                    ProgressListener* progress_listener,
+                    MuxerListener* muxer_listener,
+                    KeySource* encryption_key_source);
+
+  /// Finalize the segmenter.
+  /// @return OK on success, an error status otherwise.
+  Status Finalize();
+
+  /// Add sample to the indicated stream.
+  /// @param sample points to the sample to be added.
+  /// @return OK on success, an error status otherwise.
+  Status AddSample(scoped_refptr<MediaSample> sample);
+
+  // TODO(modmaker):  Add key source support.
+
+  /// @return true if there is an initialization range, while setting @a start
+  ///         and @a end; or false if initialization range does not apply.
+  virtual bool GetInitRangeStartAndEnd(uint32_t* start, uint32_t* end) = 0;
+
+  /// @return true if there is an index byte range, while setting @a start
+  ///         and @a end; or false if index byte range does not apply.
+  virtual bool GetIndexRangeStartAndEnd(uint32_t* start, uint32_t* end) = 0;
+
+  /// @return The total length, in seconds, of segmented media files.
+  float GetDuration() const;
+
+ protected:
+  /// Converts the given time in ISO BMFF timescale to the current WebM
+  /// timecode.
+  uint64_t FromBMFFTimescale(uint64_t time_timescale);
+  /// Converts the given time in WebM timecode to ISO BMFF timescale.
+  uint64_t FromWebMTimecode(uint64_t time_webm_timecode);
+  /// Writes the Segment header to @a writer.
+  Status WriteSegmentHeader(uint64_t file_size, MkvWriter* writer);
+  /// Creates a Cluster object with the given parameters.
+  Status SetCluster(uint64_t start_webm_timecode,
+                    uint64_t position,
+                    MkvWriter* writer);
+
+  /// Update segmentation progress using ProgressListener.
+  void UpdateProgress(uint64_t progress);
+  void set_progress_target(uint64_t target) { progress_target_ = target; }
+
+  const MuxerOptions& options() const { return options_; }
+  mkvmuxer::Cluster* cluster() { return cluster_.get(); }
+  mkvmuxer::Cues* cues() { return &cues_; }
+  MuxerListener* muxer_listener() { return muxer_listener_; }
+  MediaStream* stream() { return stream_; }
+  SeekHead* seek_head() { return &seek_head_; }
+
+  int track_id() const { return track_id_; }
+  uint64_t segment_payload_pos() const { return segment_payload_pos_; }
+  double cluster_length_sec() const { return cluster_length_sec_; }
+
+  virtual Status DoInitialize(scoped_ptr<MkvWriter> writer) = 0;
+  virtual Status DoFinalize() = 0;
+
+ private:
+  Status CreateVideoTrack(VideoStreamInfo* info);
+  Status CreateAudioTrack(AudioStreamInfo* info);
+
+  // This is called when there needs to be a new subsegment.  This does nothing
+  // in single-segment mode.  In multi-segment mode this creates a new Cluster
+  // element.
+  virtual Status NewSubsegment(uint64_t start_timescale) = 0;
+  // This is called when there needs to be a new segment.  In single-segment
+  // mode, this creates a new Cluster element.  In multi-segment mode this
+  // creates a new output file.
+  virtual Status NewSegment(uint64_t start_timescale) = 0;
+  // This is called when a segment ends.  This is called right before a call
+  // to NewSegment and at the start of Finalize.
+  Status FinalizeSegment(uint64_t end_timescale);
+
+  const MuxerOptions& options_;
+
+  scoped_ptr<mkvmuxer::Cluster> cluster_;
+  mkvmuxer::Cues cues_;
+  SeekHead seek_head_;
+  mkvmuxer::SegmentInfo segment_info_;
+  mkvmuxer::Tracks tracks_;
+
+  MediaStream* stream_;
+  MuxerListener* muxer_listener_;
+  ProgressListener* progress_listener_;
+  uint64_t progress_target_;
+  uint64_t accumulated_progress_;
+  uint64_t total_duration_;
+  uint64_t sample_duration_;
+  // The position (in bytes) of the start of the Segment payload in the init
+  // file.  This is also the size of the header before the SeekHead.
+  uint64_t segment_payload_pos_;
+
+  double cluster_length_sec_;
+  double segment_length_sec_;
+
+  int track_id_;
+
+  DISALLOW_COPY_AND_ASSIGN(Segmenter);
+};
+
+}  // namespace webm
+}  // namespace media
+}  // namespace edash_packager
+
+#endif  // MEDIA_FORMATS_WEBM_SEGMENTER_H_
diff --git a/packager/media/formats/webm/single_segment_segmenter.cc b/packager/media/formats/webm/single_segment_segmenter.cc
new file mode 100644
index 0000000000..e4cf7c6a07
--- /dev/null
+++ b/packager/media/formats/webm/single_segment_segmenter.cc
@@ -0,0 +1,88 @@
+// Copyright 2015 Google Inc. All rights reserved.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file or at
+// https://developers.google.com/open-source/licenses/bsd
+
+#include "packager/media/formats/webm/single_segment_segmenter.h"
+
+#include "packager/media/base/muxer_options.h"
+#include "packager/third_party/libwebm/src/mkvmuxer.hpp"
+
+namespace edash_packager {
+namespace media {
+namespace webm {
+
+SingleSegmentSegmenter::SingleSegmentSegmenter(const MuxerOptions& options)
+    : Segmenter(options), init_end_(0), index_start_(0) {}
+
+SingleSegmentSegmenter::~SingleSegmentSegmenter() {}
+
+Status SingleSegmentSegmenter::DoInitialize(scoped_ptr<MkvWriter> writer) {
+  writer_ = writer.Pass();
+  Status ret = WriteSegmentHeader(0, writer_.get());
+  init_end_ = writer_->Position() - 1;
+  seek_head()->set_cluster_pos(init_end_ + 1);
+  return ret;
+}
+
+Status SingleSegmentSegmenter::DoFinalize() {
+  if (!cluster()->Finalize())
+    return Status(error::FILE_FAILURE, "Error finalizing cluster.");
+
+  // Write the Cues to the end of the file.
+  index_start_ = writer_->Position();
+  if (!cues()->Write(writer_.get()))
+    return Status(error::FILE_FAILURE, "Error writing Cues data.");
+
+  uint64_t file_size = writer_->Position();
+  writer_->Position(0);
+
+  Status status = WriteSegmentHeader(file_size, writer_.get());
+  writer_->Position(file_size);
+  return status;
+}
+
+Status SingleSegmentSegmenter::NewSubsegment(uint64_t start_timescale) {
+  return Status::OK;
+}
+
+Status SingleSegmentSegmenter::NewSegment(uint64_t start_timescale) {
+  if (cluster() && !cluster()->Finalize())
+    return Status(error::FILE_FAILURE, "Error finalizing cluster.");
+
+  // Create a new Cue point.
+  uint64_t position = writer_->Position();
+  uint64_t start_webm_timecode = FromBMFFTimescale(start_timescale);
+
+  mkvmuxer::CuePoint* cue_point = new mkvmuxer::CuePoint;
+  cue_point->set_time(start_webm_timecode);
+  cue_point->set_track(track_id());
+  cue_point->set_cluster_pos(position - segment_payload_pos());
+  if (!cues()->AddCue(cue_point))
+    return Status(error::INTERNAL_ERROR, "Error adding CuePoint.");
+
+  return SetCluster(start_webm_timecode, position, writer_.get());
+}
+
+bool SingleSegmentSegmenter::GetInitRangeStartAndEnd(uint32_t* start,
+                                                     uint32_t* end) {
+  // The init range is the header, from the start of the file to the size of
+  // the header.
+  *start = 0;
+  *end = init_end_;
+  return true;
+}
+
+bool SingleSegmentSegmenter::GetIndexRangeStartAndEnd(uint32_t* start,
+                                                      uint32_t* end) {
+  // The index is the Cues element, which is always placed at the end of the
+  // file.
+  *start = index_start_;
+  *end = writer_->file()->Size();
+  return true;
+}
+
+}  // namespace webm
+}  // namespace media
+}  // namespace edash_packager
diff --git a/packager/media/formats/webm/single_segment_segmenter.h b/packager/media/formats/webm/single_segment_segmenter.h
new file mode 100644
index 0000000000..a53e85b2b9
--- /dev/null
+++ b/packager/media/formats/webm/single_segment_segmenter.h
@@ -0,0 +1,63 @@
+// Copyright 2015 Google Inc. All rights reserved.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file or at
+// https://developers.google.com/open-source/licenses/bsd
+
+#ifndef MEDIA_FORMATS_WEBM_SINGLE_SEGMENT_SEGMENTER_H_
+#define MEDIA_FORMATS_WEBM_SINGLE_SEGMENT_SEGMENTER_H_
+
+#include "packager/media/formats/webm/segmenter.h"
+
+#include "packager/base/memory/scoped_ptr.h"
+#include "packager/media/base/status.h"
+#include "packager/media/formats/webm/mkv_writer.h"
+
+namespace edash_packager {
+namespace media {
+
+struct MuxerOptions;
+
+namespace webm {
+
+/// An implementation of a Segmenter for a single-segment.  This assumes that
+/// the output file is seekable.  For non-seekable files, use
+/// TwoPassSingleSegmentSegmenter.
+class SingleSegmentSegmenter : public Segmenter {
+ public:
+  explicit SingleSegmentSegmenter(const MuxerOptions& options);
+  ~SingleSegmentSegmenter() override;
+
+  /// @name Segmenter implementation overrides.
+  /// @{
+  bool GetInitRangeStartAndEnd(uint32_t* start, uint32_t* end) override;
+  bool GetIndexRangeStartAndEnd(uint32_t* start, uint32_t* end) override;
+  /// @}
+
+ protected:
+  MkvWriter* writer() { return writer_.get(); }
+  void set_init_end(uint64_t end) { init_end_ = end; }
+  void set_index_start(uint64_t start) { index_start_ = start; }
+  void set_writer(scoped_ptr<MkvWriter> writer) { writer_ = writer.Pass(); }
+
+  // Segmenter implementation overrides.
+  Status DoInitialize(scoped_ptr<MkvWriter> writer) override;
+  Status DoFinalize() override;
+
+ private:
+  // Segmenter implementation overrides.
+  Status NewSubsegment(uint64_t start_timescale) override;
+  Status NewSegment(uint64_t start_timescale) override;
+
+  scoped_ptr<MkvWriter> writer_;
+  uint32_t init_end_;
+  uint32_t index_start_;
+
+  DISALLOW_COPY_AND_ASSIGN(SingleSegmentSegmenter);
+};
+
+}  // namespace webm
+}  // namespace media
+}  // namespace edash_packager
+
+#endif  // MEDIA_FORMATS_WEBM_SINGLE_SEGMENT_SEGMENTER_H_
diff --git a/packager/media/formats/webm/two_pass_single_segment_segmenter.cc b/packager/media/formats/webm/two_pass_single_segment_segmenter.cc
new file mode 100644
index 0000000000..b62a512f4b
--- /dev/null
+++ b/packager/media/formats/webm/two_pass_single_segment_segmenter.cc
@@ -0,0 +1,184 @@
+// Copyright 2015 Google Inc. All rights reserved.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file or at
+// https://developers.google.com/open-source/licenses/bsd
+
+#include "packager/media/formats/webm/two_pass_single_segment_segmenter.h"
+
+#include <inttypes.h>
+#include <openssl/err.h>
+#include <openssl/rand.h>
+
+#include <algorithm>
+
+#include "packager/base/files/file_path.h"
+#include "packager/base/strings/stringprintf.h"
+#include "packager/base/threading/platform_thread.h"
+#include "packager/base/time/time.h"
+#include "packager/media/base/media_sample.h"
+#include "packager/media/base/media_stream.h"
+#include "packager/media/base/muxer_options.h"
+#include "packager/media/base/stream_info.h"
+#include "packager/third_party/libwebm/src/mkvmuxer.hpp"
+#include "packager/third_party/libwebm/src/mkvmuxerutil.hpp"
+#include "packager/third_party/libwebm/src/webmids.hpp"
+
+namespace edash_packager {
+namespace media {
+namespace webm {
+namespace {
+/// Create the temp file name using process/thread id and current time.
+std::string TempFileName(const MuxerOptions& options) {
+  // TODO: Move to a common util function and remove other uses.
+  int32_t tid = static_cast<int32_t>(base::PlatformThread::CurrentId());
+  int64_t rand = 0;
+  if (RAND_bytes(reinterpret_cast<uint8_t*>(&rand), sizeof(rand)) != 1) {
+    LOG(WARNING) << "RAND_bytes failed with error: "
+                 << ERR_error_string(ERR_get_error(), NULL);
+    rand = base::Time::Now().ToInternalValue();
+  }
+  std::string file_prefix =
+      base::StringPrintf("packager-tempfile-%x-%" PRIx64 ".tmp", tid, rand);
+  return base::FilePath(options.temp_dir).Append(file_prefix).value();
+}
+
+// Skips a given number of bytes in a file by reading.  This allows
+// forward-seeking in non-seekable files.
+bool ReadSkip(File* file, int64_t byte_count) {
+  const int64_t kBufferSize = 0x40000;  // 256KB.
+  scoped_ptr<char[]> buffer(new char[kBufferSize]);
+  int64_t bytes_read = 0;
+  while (bytes_read < byte_count) {
+    int64_t size = std::min(kBufferSize, byte_count - bytes_read);
+    int64_t result = file->Read(buffer.get(), size);
+    // Only give success if there are no errors, not at EOF, and read exactly
+    // byte_count bytes.
+    if (result <= 0)
+      return false;
+
+    bytes_read += result;
+  }
+
+  DCHECK_EQ(bytes_read, byte_count);
+  return true;
+}
+}  // namespace
+
+TwoPassSingleSegmentSegmenter::TwoPassSingleSegmentSegmenter(
+    const MuxerOptions& options)
+    : SingleSegmentSegmenter(options) {}
+
+TwoPassSingleSegmentSegmenter::~TwoPassSingleSegmentSegmenter() {}
+
+Status
+TwoPassSingleSegmentSegmenter::DoInitialize(scoped_ptr<MkvWriter> writer) {
+  // Assume the amount of time to copy the temp file as the same amount
+  // of time as to make it.
+  set_progress_target(stream()->info()->duration() * 2);
+
+  real_writer_ = writer.Pass();
+
+  std::string temp_name = TempFileName(options());
+  scoped_ptr<MkvWriter> temp(new MkvWriter);
+  Status status = temp->Open(temp_name);
+  if (!status.ok())
+    return status;
+
+  return SingleSegmentSegmenter::DoInitialize(temp.Pass());
+}
+
+Status TwoPassSingleSegmentSegmenter::DoFinalize() {
+  if (!cluster()->Finalize())
+    return Status(error::FILE_FAILURE, "Error finalizing cluster.");
+
+  // Write the Cues to the end of the temp file.
+  uint64_t cues_pos = writer()->Position();
+  set_index_start(cues_pos);
+  seek_head()->set_cues_pos(cues_pos);
+  if (!cues()->Write(writer()))
+    return Status(error::FILE_FAILURE, "Error writing Cues data.");
+
+  // Write the header to the real output file.
+  Status temp = WriteSegmentHeader(writer()->Position(), real_writer_.get());
+  if (!temp.ok())
+    return temp;
+
+  // Close the temp file and open it for reading.
+  std::string temp_name = writer()->file()->file_name();
+  set_writer(scoped_ptr<MkvWriter>());
+  scoped_ptr<File, FileCloser> temp_reader(File::Open(temp_name.c_str(), "r"));
+  if (!temp_reader)
+    return Status(error::FILE_FAILURE, "Error opening temp file.");
+
+  // Skip the header that has already been written.
+  uint64_t header_size = real_writer_->Position();
+  if (!ReadSkip(temp_reader.get(), header_size))
+    return Status(error::FILE_FAILURE, "Error reading temp file.");
+
+  // Copy the rest of the data over.
+  if (!CopyFileWithClusterRewrite(temp_reader.get(), real_writer_.get(),
+                                  cluster()->Size()))
+    return Status(error::FILE_FAILURE, "Error copying temp file.");
+
+  // Close and delete the temp file.
+  temp_reader.reset();
+  if (!File::Delete(temp_name.c_str())) {
+    LOG(WARNING) << "Unable to delete temporary file " << temp_name;
+  }
+
+  // Set the writer back to the real file so GetIndexRangeStartAndEnd works.
+  set_writer(real_writer_.Pass());
+  return Status::OK;
+}
+
+bool TwoPassSingleSegmentSegmenter::CopyFileWithClusterRewrite(
+    File* source,
+    MkvWriter* dest,
+    uint64_t last_size) {
+  const int cluster_id_size = mkvmuxer::GetUIntSize(mkvmuxer::kMkvCluster);
+  const int cluster_size_size = 8;  // The size of the Cluster size integer.
+  const int cluster_header_size = cluster_id_size + cluster_size_size;
+
+  // We are at the start of a cluster, so copy the ID.
+  if (dest->WriteFromFile(source, cluster_id_size) != cluster_id_size)
+    return false;
+
+  for (int i = 0; i < cues()->cue_entries_size() - 1; ++i) {
+    // Write the size of the cluster.
+    const mkvmuxer::CuePoint* cue = cues()->GetCueByIndex(i);
+    const mkvmuxer::CuePoint* next_cue = cues()->GetCueByIndex(i + 1);
+    const int64_t cluster_payload_size =
+        next_cue->cluster_pos() - cue->cluster_pos() - cluster_header_size;
+    if (mkvmuxer::WriteUIntSize(dest, cluster_payload_size, cluster_size_size))
+      return false;
+    if (!ReadSkip(source, cluster_size_size))
+      return false;
+
+    // Copy the cluster and the next cluster's ID.
+    int64_t to_copy = cluster_payload_size + cluster_id_size;
+    if (dest->WriteFromFile(source, to_copy) != to_copy)
+      return false;
+
+    // Update the progress; need to convert from WebM timecode to ISO BMFF.
+    const uint64_t webm_delta_time = next_cue->time() - cue->time();
+    const uint64_t delta_time = FromWebMTimecode(webm_delta_time);
+    UpdateProgress(delta_time);
+  }
+
+  // The last cluster takes up until the cues.
+  const uint64_t last_cluster_payload_size = last_size - cluster_header_size;
+  if (mkvmuxer::WriteUIntSize(dest, last_cluster_payload_size,
+                              cluster_size_size))
+    return false;
+  if (!ReadSkip(source, cluster_size_size))
+    return false;
+
+  // Copy the remaining data (i.e. Cues data).
+  return dest->WriteFromFile(source) ==
+         static_cast<int64_t>(last_cluster_payload_size + cues()->Size());
+}
+
+}  // namespace webm
+}  // namespace media
+}  // namespace edash_packager
diff --git a/packager/media/formats/webm/two_pass_single_segment_segmenter.h b/packager/media/formats/webm/two_pass_single_segment_segmenter.h
new file mode 100644
index 0000000000..8293ab9bc2
--- /dev/null
+++ b/packager/media/formats/webm/two_pass_single_segment_segmenter.h
@@ -0,0 +1,52 @@
+// Copyright 2015 Google Inc. All rights reserved.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file or at
+// https://developers.google.com/open-source/licenses/bsd
+
+#ifndef MEDIA_FORMATS_WEBM_TWO_PASS_SINGLE_SEGMENT_SEGMENTER_H_
+#define MEDIA_FORMATS_WEBM_TWO_PASS_SINGLE_SEGMENT_SEGMENTER_H_
+
+#include "packager/media/formats/webm/single_segment_segmenter.h"
+
+#include "packager/base/memory/scoped_ptr.h"
+#include "packager/media/base/status.h"
+#include "packager/media/formats/webm/mkv_writer.h"
+
+namespace edash_packager {
+namespace media {
+
+struct MuxerOptions;
+
+namespace webm {
+
+/// An implementation of a Segmenter for a single-segment that performs two
+/// passes.  This does not use seeking and is used for non-seekable files.
+class TwoPassSingleSegmentSegmenter : public SingleSegmentSegmenter {
+ public:
+  explicit TwoPassSingleSegmentSegmenter(const MuxerOptions& options);
+  ~TwoPassSingleSegmentSegmenter() override;
+
+  // Segmenter implementation overrides.
+  Status DoInitialize(scoped_ptr<MkvWriter> writer) override;
+  Status DoFinalize() override;
+
+ private:
+  /// Copies the data from source to destination while rewriting the Cluster
+  /// sizes to the correct values.  This assumes that both @a source and
+  /// @a dest are at the same position and that the headers have already
+  /// been copied.
+  bool CopyFileWithClusterRewrite(File* source,
+                                  MkvWriter* dest,
+                                  uint64_t last_size);
+
+  scoped_ptr<MkvWriter> real_writer_;
+
+  DISALLOW_COPY_AND_ASSIGN(TwoPassSingleSegmentSegmenter);
+};
+
+}  // namespace webm
+}  // namespace media
+}  // namespace edash_packager
+
+#endif  // MEDIA_FORMATS_WEBM_TWO_PASS_SINGLE_SEGMENT_SEGMENTER_H_
diff --git a/packager/media/formats/webm/webm.gyp b/packager/media/formats/webm/webm.gyp
index 4e16917ad8..13e26331c6 100644
--- a/packager/media/formats/webm/webm.gyp
+++ b/packager/media/formats/webm/webm.gyp
@@ -13,6 +13,18 @@
       'target_name': 'webm',
       'type': '<(component)',
       'sources': [
+        'mkv_writer.cc',
+        'mkv_writer.h',
+        'multi_segment_segmenter.cc',
+        'multi_segment_segmenter.h',
+        'seek_head.cc',
+        'seek_head.h',
+        'segmenter.cc',
+        'segmenter.h',
+        'single_segment_segmenter.cc',
+        'single_segment_segmenter.h',
+        'two_pass_single_segment_segmenter.cc',
+        'two_pass_single_segment_segmenter.h',
         'webm_audio_client.cc',
         'webm_audio_client.h',
         'webm_cluster_parser.cc',
@@ -31,6 +43,8 @@
         'webm_parser.h',
         'webm_media_parser.cc',
         'webm_media_parser.h',
+        'webm_muxer.cc',
+        'webm_muxer.h',
         'webm_tracks_parser.cc',
         'webm_tracks_parser.h',
         'webm_video_client.cc',
@@ -39,6 +53,7 @@
         'webm_webvtt_parser.h'
       ],
       'dependencies': [
+        '../../../third_party/boringssl/boringssl.gyp:boringssl',
         '../../../third_party/libwebm/libwebm.gyp:libwebm',
         '../../base/media_base.gyp:base',
         '../../filters/filters.gyp:filters'
diff --git a/packager/media/formats/webm/webm_media_parser.cc b/packager/media/formats/webm/webm_media_parser.cc
index 82848a7150..25297e39b6 100644
--- a/packager/media/formats/webm/webm_media_parser.cc
+++ b/packager/media/formats/webm/webm_media_parser.cc
@@ -182,17 +182,25 @@ int WebMMediaParser::ParseInfoAndTracks(const uint8_t* data, int size) {
   int64_t duration_in_us = info_parser.duration() * timecode_scale_in_us;
 
   std::vector<scoped_refptr<StreamInfo>> streams;
-  scoped_refptr<AudioStreamInfo> audio_stream_info =
-      tracks_parser.audio_stream_info();
-  streams.push_back(tracks_parser.audio_stream_info());
-  streams.back()->set_duration(duration_in_us);
-  if (streams.back()->is_encrypted())
-    OnEncryptedMediaInitData(tracks_parser.audio_encryption_key_id());
+  AudioCodec audio_codec = kCodecOpus;
+  if (tracks_parser.audio_stream_info()) {
+    streams.push_back(tracks_parser.audio_stream_info());
+    streams.back()->set_duration(duration_in_us);
+    if (streams.back()->is_encrypted())
+      OnEncryptedMediaInitData(tracks_parser.audio_encryption_key_id());
+    audio_codec = tracks_parser.audio_stream_info()->codec();
+  } else {
+    VLOG(1) << "No audio track info found.";
+  }
 
-  streams.push_back(tracks_parser.video_stream_info());
-  streams.back()->set_duration(duration_in_us);
-  if (streams.back()->is_encrypted())
-    OnEncryptedMediaInitData(tracks_parser.video_encryption_key_id());
+  if (tracks_parser.video_stream_info()) {
+    streams.push_back(tracks_parser.video_stream_info());
+    streams.back()->set_duration(duration_in_us);
+    if (streams.back()->is_encrypted())
+      OnEncryptedMediaInitData(tracks_parser.video_encryption_key_id());
+  } else {
+    VLOG(1) << "No video track info found.";
+  }
 
   init_cb_.Run(streams);
 
@@ -203,8 +211,7 @@ int WebMMediaParser::ParseInfoAndTracks(const uint8_t* data, int size) {
       tracks_parser.GetVideoDefaultDuration(timecode_scale_in_us),
       tracks_parser.text_tracks(), tracks_parser.ignored_tracks(),
       tracks_parser.audio_encryption_key_id(),
-      tracks_parser.video_encryption_key_id(), audio_stream_info->codec(),
-      new_sample_cb_));
+      tracks_parser.video_encryption_key_id(), audio_codec, new_sample_cb_));
 
   return bytes_parsed;
 }
diff --git a/packager/media/formats/webm/webm_muxer.cc b/packager/media/formats/webm/webm_muxer.cc
new file mode 100644
index 0000000000..4f7f6534af
--- /dev/null
+++ b/packager/media/formats/webm/webm_muxer.cc
@@ -0,0 +1,111 @@
+// Copyright 2015 Google Inc. All rights reserved.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file or at
+// https://developers.google.com/open-source/licenses/bsd
+
+#include "packager/media/formats/webm/webm_muxer.h"
+
+#include "packager/media/base/media_sample.h"
+#include "packager/media/base/media_stream.h"
+#include "packager/media/base/stream_info.h"
+#include "packager/media/formats/webm/mkv_writer.h"
+#include "packager/media/formats/webm/multi_segment_segmenter.h"
+#include "packager/media/formats/webm/single_segment_segmenter.h"
+#include "packager/media/formats/webm/two_pass_single_segment_segmenter.h"
+
+namespace edash_packager {
+namespace media {
+namespace webm {
+
+WebMMuxer::WebMMuxer(const MuxerOptions& options) : Muxer(options) {}
+WebMMuxer::~WebMMuxer() {}
+
+Status WebMMuxer::Initialize() {
+  CHECK_EQ(streams().size(), 1U);
+
+  scoped_ptr<MkvWriter> writer(new MkvWriter);
+  Status status = writer->Open(options().output_file_name);
+  if (!status.ok())
+    return status;
+
+  if (!options().single_segment) {
+    segmenter_.reset(new MultiSegmentSegmenter(options()));
+  } else if (writer->Seekable()) {
+    segmenter_.reset(new SingleSegmentSegmenter(options()));
+  } else {
+    segmenter_.reset(new TwoPassSingleSegmentSegmenter(options()));
+  }
+
+  Status initialized =
+      segmenter_->Initialize(writer.Pass(), streams()[0], progress_listener(),
+                             muxer_listener(), encryption_key_source());
+
+  if (!initialized.ok())
+    return initialized;
+
+  FireOnMediaStartEvent();
+  return Status::OK;
+}
+
+Status WebMMuxer::Finalize() {
+  DCHECK(segmenter_);
+  Status segmenter_finalized = segmenter_->Finalize();
+
+  if (!segmenter_finalized.ok())
+    return segmenter_finalized;
+
+  FireOnMediaEndEvent();
+  LOG(INFO) << "WEBM file '" << options().output_file_name << "' finalized.";
+  return Status::OK;
+}
+
+Status WebMMuxer::DoAddSample(const MediaStream* stream,
+                              scoped_refptr<MediaSample> sample) {
+  DCHECK(segmenter_);
+  DCHECK(stream == streams()[0]);
+  return segmenter_->AddSample(sample);
+}
+
+void WebMMuxer::FireOnMediaStartEvent() {
+  if (!muxer_listener())
+    return;
+
+  DCHECK(!streams().empty()) << "Media started without a stream.";
+
+  const uint32_t timescale = streams().front()->info()->time_scale();
+  muxer_listener()->OnMediaStart(options(), *streams().front()->info(),
+                                 timescale, MuxerListener::kContainerWebM);
+}
+
+void WebMMuxer::FireOnMediaEndEvent() {
+  if (!muxer_listener())
+    return;
+
+  uint32_t init_range_start = 0;
+  uint32_t init_range_end = 0;
+  const bool has_init_range =
+      segmenter_->GetInitRangeStartAndEnd(&init_range_start, &init_range_end);
+
+  uint32_t index_range_start = 0;
+  uint32_t index_range_end = 0;
+  const bool has_index_range = segmenter_->GetIndexRangeStartAndEnd(
+      &index_range_start, &index_range_end);
+
+  const float duration_seconds = segmenter_->GetDuration();
+
+  const int64_t file_size =
+      File::GetFileSize(options().output_file_name.c_str());
+  if (file_size <= 0) {
+    LOG(ERROR) << "Invalid file size: " << file_size;
+    return;
+  }
+
+  muxer_listener()->OnMediaEnd(has_init_range, init_range_start, init_range_end,
+                               has_index_range, index_range_start,
+                               index_range_end, duration_seconds, file_size);
+}
+
+}  // namespace webm
+}  // namespace media
+}  // namespace edash_packager
diff --git a/packager/media/formats/webm/webm_muxer.h b/packager/media/formats/webm/webm_muxer.h
new file mode 100644
index 0000000000..74198d5921
--- /dev/null
+++ b/packager/media/formats/webm/webm_muxer.h
@@ -0,0 +1,44 @@
+// Copyright 2015 Google Inc. All rights reserved.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file or at
+// https://developers.google.com/open-source/licenses/bsd
+
+#ifndef MEDIA_FORMATS_WEBM_WEBM_MUXER_H_
+#define MEDIA_FORMATS_WEBM_WEBM_MUXER_H_
+
+#include "packager/media/base/muxer.h"
+
+namespace edash_packager {
+namespace media {
+namespace webm {
+
+class Segmenter;
+
+/// Implements WebM Muxer.
+class WebMMuxer : public Muxer {
+ public:
+  /// Create a WebMMuxer object from MuxerOptions.
+  explicit WebMMuxer(const MuxerOptions& options);
+  ~WebMMuxer() override;
+
+ private:
+  // Muxer implementation overrides.
+  Status Initialize() override;
+  Status Finalize() override;
+  Status DoAddSample(const MediaStream* stream,
+                     scoped_refptr<MediaSample> sample) override;
+
+  void FireOnMediaStartEvent();
+  void FireOnMediaEndEvent();
+
+  scoped_ptr<Segmenter> segmenter_;
+
+  DISALLOW_COPY_AND_ASSIGN(WebMMuxer);
+};
+
+}  // namespace webm
+}  // namespace media
+}  // namespace edash_packager
+
+#endif  // MEDIA_FORMATS_WEBM_WEBM_MUXER_H_