diff --git a/third_party/libmkv/EbmlIDs.h b/third_party/libmkv/EbmlIDs.h
new file mode 100644
index 0000000000000000000000000000000000000000..44d438583adbd2421e0f00226d9182cb61116a0b
--- /dev/null
+++ b/third_party/libmkv/EbmlIDs.h
@@ -0,0 +1,231 @@
+/*
+ *  Copyright (c) 2010 The WebM project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+#ifndef MKV_DEFS_HPP
+#define MKV_DEFS_HPP 1
+
+/* Commenting out values not available in webm, but available in matroska */
+
+enum mkv {
+  EBML = 0x1A45DFA3,
+  EBMLVersion = 0x4286,
+  EBMLReadVersion = 0x42F7,
+  EBMLMaxIDLength = 0x42F2,
+  EBMLMaxSizeLength = 0x42F3,
+  DocType = 0x4282,
+  DocTypeVersion = 0x4287,
+  DocTypeReadVersion = 0x4285,
+/* CRC_32 = 0xBF, */
+  Void = 0xEC,
+  SignatureSlot = 0x1B538667,
+  SignatureAlgo = 0x7E8A,
+  SignatureHash = 0x7E9A,
+  SignaturePublicKey = 0x7EA5,
+  Signature = 0x7EB5,
+  SignatureElements = 0x7E5B,
+  SignatureElementList = 0x7E7B,
+  SignedElement = 0x6532,
+  /* segment */
+  Segment = 0x18538067,
+  /* Meta Seek Information */
+  SeekHead = 0x114D9B74,
+  Seek = 0x4DBB,
+  SeekID = 0x53AB,
+  SeekPosition = 0x53AC,
+  /* Segment Information */
+  Info = 0x1549A966,
+/* SegmentUID = 0x73A4, */
+/* SegmentFilename = 0x7384, */
+/* PrevUID = 0x3CB923, */
+/* PrevFilename = 0x3C83AB, */
+/* NextUID = 0x3EB923, */
+/* NextFilename = 0x3E83BB, */
+/* SegmentFamily = 0x4444, */
+/* ChapterTranslate = 0x6924, */
+/* ChapterTranslateEditionUID = 0x69FC, */
+/* ChapterTranslateCodec = 0x69BF, */
+/* ChapterTranslateID = 0x69A5, */
+  TimecodeScale = 0x2AD7B1,
+  Segment_Duration = 0x4489,
+  DateUTC = 0x4461,
+/* Title = 0x7BA9, */
+  MuxingApp = 0x4D80,
+  WritingApp = 0x5741,
+  /* Cluster */
+  Cluster = 0x1F43B675,
+  Timecode = 0xE7,
+/* SilentTracks = 0x5854, */
+/* SilentTrackNumber = 0x58D7, */
+/* Position = 0xA7, */
+  PrevSize = 0xAB,
+  BlockGroup = 0xA0,
+  Block = 0xA1,
+/* BlockVirtual = 0xA2, */
+  BlockAdditions = 0x75A1,
+  BlockMore = 0xA6,
+  BlockAddID = 0xEE,
+  BlockAdditional = 0xA5,
+  BlockDuration = 0x9B,
+/* ReferencePriority = 0xFA, */
+  ReferenceBlock = 0xFB,
+/* ReferenceVirtual = 0xFD, */
+/* CodecState = 0xA4, */
+/* Slices = 0x8E, */
+/* TimeSlice = 0xE8, */
+  LaceNumber = 0xCC,
+/* FrameNumber = 0xCD, */
+/* BlockAdditionID = 0xCB, */
+/* MkvDelay = 0xCE, */
+/* Cluster_Duration = 0xCF, */
+  SimpleBlock = 0xA3,
+/* EncryptedBlock = 0xAF, */
+  /* Track */
+  Tracks = 0x1654AE6B,
+  TrackEntry = 0xAE,
+  TrackNumber = 0xD7,
+  TrackUID = 0x73C5,
+  TrackType = 0x83,
+  FlagEnabled = 0xB9,
+  FlagDefault = 0x88,
+  FlagForced = 0x55AA,
+  FlagLacing = 0x9C,
+/* MinCache = 0x6DE7, */
+/* MaxCache = 0x6DF8, */
+  DefaultDuration = 0x23E383,
+/* TrackTimecodeScale = 0x23314F, */
+/* TrackOffset = 0x537F, */
+  MaxBlockAdditionID = 0x55EE,
+  Name = 0x536E,
+  Language = 0x22B59C,
+  CodecID = 0x86,
+  CodecPrivate = 0x63A2,
+  CodecName = 0x258688,
+/* AttachmentLink = 0x7446, */
+/* CodecSettings = 0x3A9697, */
+/* CodecInfoURL = 0x3B4040, */
+/* CodecDownloadURL = 0x26B240, */
+/* CodecDecodeAll = 0xAA, */
+/* TrackOverlay = 0x6FAB, */
+/* TrackTranslate = 0x6624, */
+/* TrackTranslateEditionUID = 0x66FC, */
+/* TrackTranslateCodec = 0x66BF, */
+/* TrackTranslateTrackID = 0x66A5, */
+  /* video */
+  Video = 0xE0,
+  FlagInterlaced = 0x9A,
+  StereoMode = 0x53B8,
+  AlphaMode = 0x53C0,
+  PixelWidth = 0xB0,
+  PixelHeight = 0xBA,
+  PixelCropBottom = 0x54AA,
+  PixelCropTop = 0x54BB,
+  PixelCropLeft = 0x54CC,
+  PixelCropRight = 0x54DD,
+  DisplayWidth = 0x54B0,
+  DisplayHeight = 0x54BA,
+  DisplayUnit = 0x54B2,
+  AspectRatioType = 0x54B3,
+/* ColourSpace = 0x2EB524, */
+/* GammaValue = 0x2FB523, */
+  FrameRate = 0x2383E3,
+  /* end video */
+  /* audio */
+  Audio = 0xE1,
+  SamplingFrequency = 0xB5,
+  OutputSamplingFrequency = 0x78B5,
+  Channels = 0x9F,
+/* ChannelPositions = 0x7D7B, */
+  BitDepth = 0x6264,
+  /* end audio */
+  /* content encoding */
+/* ContentEncodings = 0x6d80, */
+/* ContentEncoding = 0x6240, */
+/* ContentEncodingOrder = 0x5031, */
+/* ContentEncodingScope = 0x5032, */
+/* ContentEncodingType = 0x5033, */
+/* ContentCompression = 0x5034, */
+/* ContentCompAlgo = 0x4254, */
+/* ContentCompSettings = 0x4255, */
+/* ContentEncryption = 0x5035, */
+/* ContentEncAlgo = 0x47e1, */
+/* ContentEncKeyID = 0x47e2, */
+/* ContentSignature = 0x47e3, */
+/* ContentSigKeyID = 0x47e4, */
+/* ContentSigAlgo = 0x47e5, */
+/* ContentSigHashAlgo = 0x47e6, */
+  /* end content encoding */
+  /* Cueing Data */
+  Cues = 0x1C53BB6B,
+  CuePoint = 0xBB,
+  CueTime = 0xB3,
+  CueTrackPositions = 0xB7,
+  CueTrack = 0xF7,
+  CueClusterPosition = 0xF1,
+  CueBlockNumber = 0x5378
+/* CueCodecState = 0xEA, */
+/* CueReference = 0xDB, */
+/* CueRefTime = 0x96, */
+/* CueRefCluster = 0x97, */
+/* CueRefNumber = 0x535F, */
+/* CueRefCodecState = 0xEB, */
+  /* Attachment */
+/* Attachments = 0x1941A469, */
+/* AttachedFile = 0x61A7, */
+/* FileDescription = 0x467E, */
+/* FileName = 0x466E, */
+/* FileMimeType = 0x4660, */
+/* FileData = 0x465C, */
+/* FileUID = 0x46AE, */
+/* FileReferral = 0x4675, */
+  /* Chapters */
+/* Chapters = 0x1043A770, */
+/* EditionEntry = 0x45B9, */
+/* EditionUID = 0x45BC, */
+/* EditionFlagHidden = 0x45BD, */
+/* EditionFlagDefault = 0x45DB, */
+/* EditionFlagOrdered = 0x45DD, */
+/* ChapterAtom = 0xB6, */
+/* ChapterUID = 0x73C4, */
+/* ChapterTimeStart = 0x91, */
+/* ChapterTimeEnd = 0x92, */
+/* ChapterFlagHidden = 0x98, */
+/* ChapterFlagEnabled = 0x4598, */
+/* ChapterSegmentUID = 0x6E67, */
+/* ChapterSegmentEditionUID = 0x6EBC, */
+/* ChapterPhysicalEquiv = 0x63C3, */
+/* ChapterTrack = 0x8F, */
+/* ChapterTrackNumber = 0x89, */
+/* ChapterDisplay = 0x80, */
+/* ChapString = 0x85, */
+/* ChapLanguage = 0x437C, */
+/* ChapCountry = 0x437E, */
+/* ChapProcess = 0x6944, */
+/* ChapProcessCodecID = 0x6955, */
+/* ChapProcessPrivate = 0x450D, */
+/* ChapProcessCommand = 0x6911, */
+/* ChapProcessTime = 0x6922, */
+/* ChapProcessData = 0x6933, */
+  /* Tagging */
+/* Tags = 0x1254C367, */
+/* Tag = 0x7373, */
+/* Targets = 0x63C0, */
+/* TargetTypeValue = 0x68CA, */
+/* TargetType = 0x63CA, */
+/* Tagging_TrackUID = 0x63C5, */
+/* Tagging_EditionUID = 0x63C9, */
+/* Tagging_ChapterUID = 0x63C4, */
+/* AttachmentUID = 0x63C6, */
+/* SimpleTag = 0x67C8, */
+/* TagName = 0x45A3, */
+/* TagLanguage = 0x447A, */
+/* TagDefault = 0x4484, */
+/* TagString = 0x4487, */
+/* TagBinary = 0x4485, */
+};
+#endif
diff --git a/third_party/libmkv/EbmlWriter.c b/third_party/libmkv/EbmlWriter.c
new file mode 100644
index 0000000000000000000000000000000000000000..27cfe861ce4c81008f69caaf32294dff51edd945
--- /dev/null
+++ b/third_party/libmkv/EbmlWriter.c
@@ -0,0 +1,157 @@
+/*
+ *  Copyright (c) 2010 The WebM project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+#include "EbmlWriter.h"
+#include <stdlib.h>
+#include <wchar.h>
+#include <string.h>
+#include <limits.h>
+#if defined(_MSC_VER)
+#define LITERALU64(n) n
+#else
+#define LITERALU64(n) n##LLU
+#endif
+
+void Ebml_WriteLen(EbmlGlobal *glob, int64_t val) {
+  /* TODO check and make sure we are not > than 0x0100000000000000LLU */
+  unsigned char size = 8; /* size in bytes to output */
+
+  /* mask to compare for byte size */
+  int64_t minVal = 0xff;
+
+  for (size = 1; size < 8; size ++) {
+    if (val < minVal)
+      break;
+
+    minVal = (minVal << 7);
+  }
+
+  val |= (((uint64_t)0x80) << ((size - 1) * 7));
+
+  Ebml_Serialize(glob, (void *) &val, sizeof(val), size);
+}
+
+void Ebml_WriteString(EbmlGlobal *glob, const char *str) {
+  const size_t size_ = strlen(str);
+  const uint64_t  size = size_;
+  Ebml_WriteLen(glob, size);
+  /* TODO: it's not clear from the spec whether the nul terminator
+   * should be serialized too.  For now we omit the null terminator.
+   */
+  Ebml_Write(glob, str, (unsigned long)size);
+}
+
+void Ebml_WriteUTF8(EbmlGlobal *glob, const wchar_t *wstr) {
+  const size_t strlen = wcslen(wstr);
+
+  /* TODO: it's not clear from the spec whether the nul terminator
+   * should be serialized too.  For now we include it.
+   */
+  const uint64_t  size = strlen;
+
+  Ebml_WriteLen(glob, size);
+  Ebml_Write(glob, wstr, (unsigned long)size);
+}
+
+void Ebml_WriteID(EbmlGlobal *glob, unsigned long class_id) {
+  int len;
+
+  if (class_id >= 0x01000000)
+    len = 4;
+  else if (class_id >= 0x00010000)
+    len = 3;
+  else if (class_id >= 0x00000100)
+    len = 2;
+  else
+    len = 1;
+
+  Ebml_Serialize(glob, (void *)&class_id, sizeof(class_id), len);
+}
+
+void Ebml_SerializeUnsigned64(EbmlGlobal *glob, unsigned long class_id, uint64_t ui) {
+  unsigned char sizeSerialized = 8 | 0x80;
+  Ebml_WriteID(glob, class_id);
+  Ebml_Serialize(glob, &sizeSerialized, sizeof(sizeSerialized), 1);
+  Ebml_Serialize(glob, &ui, sizeof(ui), 8);
+}
+
+void Ebml_SerializeUnsigned(EbmlGlobal *glob, unsigned long class_id, unsigned long ui) {
+  unsigned char size = 8; /* size in bytes to output */
+  unsigned char sizeSerialized = 0;
+  unsigned long minVal;
+
+  Ebml_WriteID(glob, class_id);
+  minVal = 0x7fLU; /* mask to compare for byte size */
+
+  for (size = 1; size < 4; size ++) {
+    if (ui < minVal) {
+      break;
+    }
+
+    minVal <<= 7;
+  }
+
+  sizeSerialized = 0x80 | size;
+  Ebml_Serialize(glob, &sizeSerialized, sizeof(sizeSerialized), 1);
+  Ebml_Serialize(glob, &ui, sizeof(ui), size);
+}
+/* TODO: perhaps this is a poor name for this id serializer helper function */
+void Ebml_SerializeBinary(EbmlGlobal *glob, unsigned long class_id, unsigned long bin) {
+  int size;
+  for (size = 4; size > 1; size--) {
+    if (bin & (unsigned int)0x000000ff << ((size - 1) * 8))
+      break;
+  }
+  Ebml_WriteID(glob, class_id);
+  Ebml_WriteLen(glob, size);
+  Ebml_WriteID(glob, bin);
+}
+
+void Ebml_SerializeFloat(EbmlGlobal *glob, unsigned long class_id, double d) {
+  unsigned char len = 0x88;
+
+  Ebml_WriteID(glob, class_id);
+  Ebml_Serialize(glob, &len, sizeof(len), 1);
+  Ebml_Serialize(glob,  &d, sizeof(d), 8);
+}
+
+void Ebml_WriteSigned16(EbmlGlobal *glob, short val) {
+  signed long out = ((val & 0x003FFFFF) | 0x00200000) << 8;
+  Ebml_Serialize(glob, &out, sizeof(out), 3);
+}
+
+void Ebml_SerializeString(EbmlGlobal *glob, unsigned long class_id, const char *s) {
+  Ebml_WriteID(glob, class_id);
+  Ebml_WriteString(glob, s);
+}
+
+void Ebml_SerializeUTF8(EbmlGlobal *glob, unsigned long class_id, wchar_t *s) {
+  Ebml_WriteID(glob,  class_id);
+  Ebml_WriteUTF8(glob,  s);
+}
+
+void Ebml_SerializeData(EbmlGlobal *glob, unsigned long class_id, unsigned char *data, unsigned long data_length) {
+  Ebml_WriteID(glob, class_id);
+  Ebml_WriteLen(glob, data_length);
+  Ebml_Write(glob,  data, data_length);
+}
+
+void Ebml_WriteVoid(EbmlGlobal *glob, unsigned long vSize) {
+  unsigned char tmp = 0;
+  unsigned long i = 0;
+
+  Ebml_WriteID(glob, 0xEC);
+  Ebml_WriteLen(glob, vSize);
+
+  for (i = 0; i < vSize; i++) {
+    Ebml_Write(glob, &tmp, 1);
+  }
+}
+
+/* TODO Serialize Date */
diff --git a/third_party/libmkv/EbmlWriter.h b/third_party/libmkv/EbmlWriter.h
new file mode 100644
index 0000000000000000000000000000000000000000..b94f757332f0acd2900038b8835ca00e62f47fda
--- /dev/null
+++ b/third_party/libmkv/EbmlWriter.h
@@ -0,0 +1,42 @@
+/*
+ *  Copyright (c) 2010 The WebM project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+#ifndef EBMLWRITER_HPP
+#define EBMLWRITER_HPP
+#include <stddef.h>
+#include "vpx/vpx_integer.h"
+
+/* note: you must define write and serialize functions as well as your own
+ * EBML_GLOBAL
+ *
+ * These functions MUST be implemented
+ */
+
+typedef struct EbmlGlobal EbmlGlobal;
+void  Ebml_Serialize(EbmlGlobal *glob, const void *, int, unsigned long);
+void  Ebml_Write(EbmlGlobal *glob, const void *, unsigned long);
+
+/*****/
+
+void Ebml_WriteLen(EbmlGlobal *glob, int64_t val);
+void Ebml_WriteString(EbmlGlobal *glob, const char *str);
+void Ebml_WriteUTF8(EbmlGlobal *glob, const wchar_t *wstr);
+void Ebml_WriteID(EbmlGlobal *glob, unsigned long class_id);
+void Ebml_SerializeUnsigned64(EbmlGlobal *glob, unsigned long class_id, uint64_t ui);
+void Ebml_SerializeUnsigned(EbmlGlobal *glob, unsigned long class_id, unsigned long ui);
+void Ebml_SerializeBinary(EbmlGlobal *glob, unsigned long class_id, unsigned long ui);
+void Ebml_SerializeFloat(EbmlGlobal *glob, unsigned long class_id, double d);
+/* TODO make this more generic to signed */
+void Ebml_WriteSigned16(EbmlGlobal *glob, short val);
+void Ebml_SerializeString(EbmlGlobal *glob, unsigned long class_id, const char *s);
+void Ebml_SerializeUTF8(EbmlGlobal *glob, unsigned long class_id, wchar_t *s);
+void Ebml_SerializeData(EbmlGlobal *glob, unsigned long class_id, unsigned char *data, unsigned long data_length);
+void Ebml_WriteVoid(EbmlGlobal *glob, unsigned long vSize);
+/* TODO need date function */
+#endif