Adding ChunkDemuxer implementation.

BUG=86536
TEST=ChunkDemuxerTest.*

Review URL: http://codereview.chromium.org/7203002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@90966 0039d316-1c4b-4281-b951-d872f2087c98

11 files changed, 1287 insertions, 0 deletions

diff --git a/media/webm/cluster_builder.cc b/media/webm/cluster_builder.cc
new file mode 100644
index 0000000..eb5fbfb
--- /dev/null
+++ b/media/webm/cluster_builder.cc
@@ -0,0 +1,128 @@
+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "media/webm/cluster_builder.h"
+
+#include "base/logging.h"
+#include "media/base/data_buffer.h"
+
+namespace media {
+
+static const uint8 kClusterHeader[] = {
+  0x1F, 0x43, 0xB6, 0x75,  // CLUSTER ID
+  0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,  // cluster(size = 0)
+  0xE7,  // Timecode ID
+  0x88,  // timecode(size=8)
+  0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,  // timecode value
+};
+
+const int kClusterHeaderSize = sizeof(kClusterHeader);
+const int kClusterSizeOffset = 4;
+const int kClusterTimecodeOffset = 14;
+
+static const uint8 kSimpleBlockHeader[] = {
+  0xA3,  // SimpleBlock ID
+  0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,  // SimpleBlock(size = 0)
+};
+
+const int kSimpleBlockHeaderSize = sizeof(kSimpleBlockHeader);
+const int kSimpleBlockSizeOffset = 1;
+
+const int kInitialBufferSize = 32768;
+
+Cluster::Cluster(const uint8* data, int size) : data_(data), size_(size) {}
+Cluster::~Cluster() {}
+
+ClusterBuilder::ClusterBuilder() { Reset(); }
+
+void ClusterBuilder::SetClusterTimecode(int64 cluster_timecode) {
+  DCHECK_EQ(cluster_timecode_, -1);
+
+  cluster_timecode_ = cluster_timecode;
+
+  // Write the timecode into the header.
+  uint8* buf = buffer_.get() + kClusterTimecodeOffset;
+  for (int i = 7; i >= 0; --i) {
+    buf[i] = cluster_timecode & 0xff;
+    cluster_timecode >>= 8;
+  }
+}
+
+void ClusterBuilder::AddSimpleBlock(int track_num, int64 timecode, int flags,
+                                    const uint8* data, int size) {
+  DCHECK_GE(track_num, 0);
+  DCHECK_LE(track_num, 126);
+  DCHECK_GE(flags, 0);
+  DCHECK_LE(flags, 0xff);
+  DCHECK(data);
+  DCHECK_GT(size, 0);
+  DCHECK_NE(cluster_timecode_, -1);
+
+  int64 timecode_delta = timecode - cluster_timecode_;
+  DCHECK_GE(timecode_delta, -32768);
+  DCHECK_LE(timecode_delta, 32767);
+
+  int block_size = 4 + size;
+  int bytes_needed = kSimpleBlockHeaderSize + block_size;
+  if (bytes_needed > (buffer_size_ - bytes_used_))
+    ExtendBuffer(bytes_needed);
+
+  uint8* buf = buffer_.get() + bytes_used_;
+  int block_offset = bytes_used_;
+  memcpy(buf, kSimpleBlockHeader, kSimpleBlockHeaderSize);
+  UpdateUInt64(block_offset + kSimpleBlockSizeOffset, block_size);
+  buf += kSimpleBlockHeaderSize;
+
+  buf[0] = 0x80 | (track_num & 0x7F);
+  buf[1] = (timecode_delta >> 8) & 0xff;
+  buf[2] = timecode_delta & 0xff;
+  buf[3] = flags & 0xff;
+  memcpy(buf + 4, data, size);
+
+  bytes_used_ += bytes_needed;
+}
+
+Cluster* ClusterBuilder::Finish() {
+  DCHECK_NE(cluster_timecode_, -1);
+
+  UpdateUInt64(kClusterSizeOffset, bytes_used_ - (kClusterSizeOffset + 8));
+
+  scoped_ptr<Cluster> ret(new Cluster(buffer_.release(), bytes_used_));
+  Reset();
+  return ret.release();
+}
+
+void ClusterBuilder::Reset() {
+  buffer_size_ = kInitialBufferSize;
+  buffer_.reset(new uint8[buffer_size_]);
+  memcpy(buffer_.get(), kClusterHeader, kClusterHeaderSize);
+  bytes_used_ = kClusterHeaderSize;
+  cluster_timecode_ = -1;
+}
+
+void ClusterBuilder::ExtendBuffer(int bytes_needed) {
+  int new_buffer_size = 2 * buffer_size_;
+
+  while ((new_buffer_size - bytes_used_) < bytes_needed)
+    new_buffer_size *= 2;
+
+  scoped_array<uint8> new_buffer(new uint8[new_buffer_size]);
+
+  memcpy(new_buffer.get(), buffer_.get(), bytes_used_);
+  buffer_.reset(new_buffer.release());
+  buffer_size_ = new_buffer_size;
+}
+
+void ClusterBuilder::UpdateUInt64(int offset, int64 value) {
+  DCHECK_LE(offset + 7, buffer_size_);
+  uint8* buf = buffer_.get() + offset;
+
+  // Fill the last 7 bytes of size field in big-endian order.
+  for (int i = 7; i > 0; i--) {
+    buf[i] = value & 0xff;
+    value >>= 8;
+  }
+}
+
+}  // namespace media
diff --git a/media/webm/cluster_builder.h b/media/webm/cluster_builder.h
new file mode 100644
index 0000000..3ff30ab
--- /dev/null
+++ b/media/webm/cluster_builder.h
@@ -0,0 +1,55 @@
+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef MEDIA_WEBM_CLUSTER_BUILDER_H_
+#define MEDIA_WEBM_CLUSTER_BUILDER_H_
+
+#include "base/basictypes.h"
+#include "base/scoped_ptr.h"
+#include "media/base/buffers.h"
+
+namespace media {
+
+class Cluster {
+ public:
+  // Takes ownership of |data|
+  Cluster(const uint8* data, int size);
+  ~Cluster();
+
+  const uint8* data() const { return data_.get(); }
+  int size() const { return size_; }
+
+ private:
+  scoped_array<const uint8> data_;
+  int size_;
+
+  DISALLOW_IMPLICIT_CONSTRUCTORS(Cluster);
+};
+
+class ClusterBuilder {
+ public:
+  ClusterBuilder();
+
+  void SetClusterTimecode(int64 cluster_timecode);
+  void AddSimpleBlock(int track_num, int64 timecode, int flags,
+                      const uint8* data, int size);
+
+  Cluster* Finish();
+
+ private:
+  void Reset();
+  void ExtendBuffer(int bytes_needed);
+  void UpdateUInt64(int offset, int64 value);
+
+  scoped_array<uint8> buffer_;
+  int buffer_size_;
+  int bytes_used_;
+  int64 cluster_timecode_;
+
+  DISALLOW_COPY_AND_ASSIGN(ClusterBuilder);
+};
+
+}  // namespace media
+
+#endif  // MEDIA_WEBM_CLUSTER_BUILDER_H_
diff --git a/media/webm/webm_cluster_parser.cc b/media/webm/webm_cluster_parser.cc
new file mode 100644
index 0000000..8eb045c
--- /dev/null
+++ b/media/webm/webm_cluster_parser.cc
@@ -0,0 +1,133 @@
+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "media/webm/webm_cluster_parser.h"
+
+#include "base/logging.h"
+#include "media/base/data_buffer.h"
+#include "media/webm/webm_constants.h"
+
+namespace media {
+
+static Buffer* CreateBuffer(const uint8* data, size_t size) {
+  scoped_array<uint8> buf(new uint8[size]);
+  memcpy(buf.get(), data, size);
+  return new DataBuffer(buf.release(), size);
+}
+
+WebMClusterParser::WebMClusterParser(int64 timecode_scale,
+                                     int audio_track_num,
+                                     base::TimeDelta audio_default_duration,
+                                     int video_track_num,
+                                     base::TimeDelta video_default_duration)
+    : timecode_multiplier_(timecode_scale / 1000.0),
+      audio_track_num_(audio_track_num),
+      audio_default_duration_(audio_default_duration),
+      video_track_num_(video_track_num),
+      video_default_duration_(video_default_duration),
+      last_block_timecode_(-1),
+      cluster_timecode_(-1) {
+}
+
+WebMClusterParser::~WebMClusterParser() {}
+
+int WebMClusterParser::Parse(const uint8* buf, int size) {
+  last_block_timecode_ = -1;
+  cluster_timecode_ = -1;
+  audio_buffers_.clear();
+  video_buffers_.clear();
+
+  return WebMParseListElement(buf, size, kWebMIdCluster, 1, this);
+}
+
+bool WebMClusterParser::OnListStart(int id) {
+  if (id == kWebMIdCluster)
+    cluster_timecode_ = -1;
+
+  return true;
+}
+
+bool WebMClusterParser::OnListEnd(int id) {
+  if (id == kWebMIdCluster)
+    cluster_timecode_ = -1;
+
+  return true;
+}
+
+bool WebMClusterParser::OnUInt(int id, int64 val) {
+  if (id == kWebMIdTimecode) {
+    if (cluster_timecode_ != -1)
+      return false;
+
+    cluster_timecode_ = val;
+  }
+
+  return true;
+}
+
+bool WebMClusterParser::OnFloat(int id, double val) {
+  VLOG(1) << "Unexpected float element with ID " << std::hex << id;
+  return false;
+}
+
+bool WebMClusterParser::OnBinary(int id, const uint8* data, int size) {
+  VLOG(1) << "Unexpected binary element with ID " << std::hex << id;
+  return false;
+}
+
+bool WebMClusterParser::OnString(int id, const std::string& str) {
+  VLOG(1) << "Unexpected string element with ID " << std::hex << id;
+  return false;
+}
+
+bool WebMClusterParser::OnSimpleBlock(int track_num, int timecode,
+                                      int flags,
+                                      const uint8* data, int size) {
+  if (cluster_timecode_ == -1) {
+    VLOG(1) << "Got SimpleBlock before cluster timecode.";
+    return false;
+  }
+
+  if (timecode < 0) {
+    VLOG(1) << "Got SimpleBlock with negative timecode offset " << timecode;
+    return false;
+  }
+
+  if (last_block_timecode_ != -1 && timecode < last_block_timecode_) {
+    VLOG(1) << "Got SimpleBlock with a timecode before the previous block.";
+    return false;
+  }
+
+  last_block_timecode_ = timecode;
+
+  base::TimeDelta timestamp = base::TimeDelta::FromMicroseconds(
+      (cluster_timecode_ + timecode) * timecode_multiplier_);
+
+  scoped_refptr<Buffer> buffer(CreateBuffer(data, size));
+  buffer->SetTimestamp(timestamp);
+  BufferQueue* queue = NULL;
+
+  if (track_num == audio_track_num_) {
+    buffer->SetDuration(audio_default_duration_);
+    queue = &audio_buffers_;
+  } else if (track_num == video_track_num_) {
+    buffer->SetDuration(video_default_duration_);
+    queue = &video_buffers_;
+  } else {
+    VLOG(1) << "Unexpected track number " << track_num;
+    return false;
+  }
+
+  if (!queue->empty() &&
+      buffer->GetTimestamp() == queue->back()->GetTimestamp()) {
+    VLOG(1) << "Got SimpleBlock timecode is not strictly monotonically "
+            << "increasing for track " << track_num;
+    return false;
+  }
+
+  queue->push_back(buffer);
+  return true;
+}
+
+}  // namespace media
diff --git a/media/webm/webm_cluster_parser.h b/media/webm/webm_cluster_parser.h
new file mode 100644
index 0000000..98c5854
--- /dev/null
+++ b/media/webm/webm_cluster_parser.h
@@ -0,0 +1,65 @@
+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef MEDIA_WEBM_WEBM_CLUSTER_PARSER_H_
+#define MEDIA_WEBM_WEBM_CLUSTER_PARSER_H_
+
+#include <deque>
+
+#include "base/scoped_ptr.h"
+#include "media/base/buffers.h"
+#include "media/webm/webm_parser.h"
+
+namespace media {
+
+class WebMClusterParser : public WebMParserClient {
+ public:
+  typedef std::deque<scoped_refptr<Buffer> > BufferQueue;
+
+  WebMClusterParser(int64 timecode_scale,
+                    int audio_track_num,
+                    base::TimeDelta audio_default_duration,
+                    int video_track_num,
+                    base::TimeDelta video_default_duration);
+  virtual ~WebMClusterParser();
+
+  // Parses a WebM cluster element in |buf|.
+  //
+  // Returns the number of bytes parsed on success. Returns -1
+  // if a parse error occurs.
+  int Parse(const uint8* buf, int size);
+
+  const BufferQueue& audio_buffers() const { return audio_buffers_; }
+  const BufferQueue& video_buffers() const { return video_buffers_; }
+
+ private:
+  // WebMParserClient methods.
+  virtual bool OnListStart(int id);
+  virtual bool OnListEnd(int id);
+  virtual bool OnUInt(int id, int64 val);
+  virtual bool OnFloat(int id, double val);
+  virtual bool OnBinary(int id, const uint8* data, int size);
+  virtual bool OnString(int id, const std::string& str);
+  virtual bool OnSimpleBlock(int track_num, int timecode, int flags,
+                             const uint8* data, int size);
+
+  double timecode_multiplier_; // Multiplier used to convert timecodes into
+                               // microseconds.
+  int audio_track_num_;
+  base::TimeDelta audio_default_duration_;
+  int video_track_num_;
+  base::TimeDelta  video_default_duration_;
+
+  int64 last_block_timecode_;
+
+  int64 cluster_timecode_;
+  BufferQueue audio_buffers_;
+  BufferQueue video_buffers_;
+
+  DISALLOW_IMPLICIT_CONSTRUCTORS(WebMClusterParser);
+};
+
+}  // namespace media
+
+#endif // MEDIA_WEBM_WEBM_CLUSTER_PARSER_H_
diff --git a/media/webm/webm_constants.h b/media/webm/webm_constants.h
new file mode 100644
index 0000000..aa6dda0
--- /dev/null
+++ b/media/webm/webm_constants.h
@@ -0,0 +1,70 @@
+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef MEDIA_WEBM_WEBM_CONSTANTS_H_
+#define MEDIA_WEBM_WEBM_CONSTANTS_H_
+
+namespace media {
+
+// WebM element IDs.
+// This is a subset of the IDs in the Matroska spec.
+// http://www.matroska.org/technical/specs/index.html
+const int kWebMIdAspectRatioType = 0x54B3;
+const int kWebMIdAudio = 0xE1;
+const int kWebMIdBitDepth = 0x6264;
+const int kWebMIdBlock = 0xA1;
+const int kWebMIdBlockGroup = 0xA0;
+const int kWebMIdChannels = 0x9F;
+const int kWebMIdCluster = 0x1f43b675;
+const int kWebMIdCodecID = 0x86;
+const int kWebMIdCodecName = 0x258688;
+const int kWebMIdCodecPrivate = 0x63A2;
+const int kWebMIdDateUTC = 0x4461;
+const int kWebMIdDefaultDuration = 0x23E383;
+const int kWebMIdDisplayHeight = 0x54BA;
+const int kWebMIdDisplayUnit = 0x54B2;
+const int kWebMIdDisplayWidth = 0x54B0;
+const int kWebMIdDuration = 0x4489;
+const int kWebMIdFlagDefault = 0x88;
+const int kWebMIdFlagEnabled = 0xB9;
+const int kWebMIdFlagForced = 0x55AA;
+const int kWebMIdFlagInterlaced = 0x9A;
+const int kWebMIdFlagLacing = 0x9C;
+const int kWebMIdInfo = 0x1549A966;
+const int kWebMIdLanguage = 0x22B59C;
+const int kWebMIdMuxingApp = 0x4D80;
+const int kWebMIdName = 0x536E;
+const int kWebMIdOutputSamplingFrequency = 0x78B5;
+const int kWebMIdPixelCropBottom = 0x54AA;
+const int kWebMIdPixelCropLeft = 0x54CC;
+const int kWebMIdPixelCropRight = 0x54DD;
+const int kWebMIdPixelCropTop = 0x54BB;
+const int kWebMIdPixelHeight = 0xBA;
+const int kWebMIdPixelWidth = 0xB0;
+const int kWebMIdSamplingFrequency = 0xB5;
+const int kWebMIdSegmentUID = 0x73A4;
+const int kWebMIdSimpleBlock = 0xA3;
+const int kWebMIdStereoMode = 0x53B8;
+const int kWebMIdTimecode = 0xE7;
+const int kWebMIdTimecodeScale = 0x2AD7B1;
+const int kWebMIdTitle = 0x7BA9;
+const int kWebMIdTrackEntry = 0xAE;
+const int kWebMIdTrackNumber = 0xD7;
+const int kWebMIdTrackType = 0x83;
+const int kWebMIdTrackUID = 0x73C5;
+const int kWebMIdTracks = 0x1654AE6B;
+const int kWebMIdVideo = 0xE0;
+const int kWebMIdWritingApp = 0x5741;
+
+// Default timecode scale if the TimecodeScale element is
+// not specified in the INFO element.
+const int kWebMDefaultTimecodeScale = 1000000;
+
+// Values for TrackType element.
+const int kWebMTrackTypeVideo = 1;
+const int kWebMTrackTypeAudio = 2;
+
+}  // namespace media
+
+#endif  // MEDIA_WEBM_WEBM_CONSTANTS_H_
diff --git a/media/webm/webm_info_parser.cc b/media/webm/webm_info_parser.cc
new file mode 100644
index 0000000..41e1a25
--- /dev/null
+++ b/media/webm/webm_info_parser.cc
@@ -0,0 +1,75 @@
+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "media/webm/webm_info_parser.h"
+
+#include "base/logging.h"
+#include "media/webm/webm_constants.h"
+
+namespace media {
+
+WebMInfoParser::WebMInfoParser()
+    : timecode_scale_(-1),
+      duration_(-1) {
+}
+
+WebMInfoParser::~WebMInfoParser() {}
+
+int WebMInfoParser::Parse(const uint8* buf, int size) {
+  return WebMParseListElement(buf, size, kWebMIdInfo, 1, this);
+}
+
+bool WebMInfoParser::OnListStart(int id) { return true; }
+
+bool WebMInfoParser::OnListEnd(int id) {
+  if (id == kWebMIdInfo && timecode_scale_ == -1) {
+    // Set timecode scale to default value if it isn't present in
+    // the Info element.
+    timecode_scale_ = kWebMDefaultTimecodeScale;
+  }
+  return true;
+}
+
+bool WebMInfoParser::OnUInt(int id, int64 val) {
+  if (id != kWebMIdTimecodeScale)
+    return true;
+
+  if (timecode_scale_ != -1) {
+    VLOG(1) << "Multiple values for id " << std::hex << id << " specified";
+    return false;
+  }
+
+  timecode_scale_ = val;
+  return true;
+}
+
+bool WebMInfoParser::OnFloat(int id, double val) {
+  if (id != kWebMIdDuration) {
+    VLOG(1) << "Unexpected float for id" << std::hex << id;
+    return false;
+  }
+
+  if (duration_ != -1) {
+    VLOG(1) << "Multiple values for duration.";
+    return false;
+  }
+
+  duration_ = val;
+  return true;
+}
+
+bool WebMInfoParser::OnBinary(int id, const uint8* data, int size) {
+  return true;
+}
+
+bool WebMInfoParser::OnString(int id, const std::string& str) {
+  return true;
+}
+
+bool WebMInfoParser::OnSimpleBlock(int track_num, int timecode, int flags,
+                                   const uint8* data, int size) {
+  return false;
+}
+
+}  // namespace media
diff --git a/media/webm/webm_info_parser.h b/media/webm/webm_info_parser.h
new file mode 100644
index 0000000..6391f8b
--- /dev/null
+++ b/media/webm/webm_info_parser.h
@@ -0,0 +1,46 @@
+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef MEDIA_WEBM_WEBM_INFO_PARSER_H_
+#define MEDIA_WEBM_WEBM_INFO_PARSER_H_
+
+#include "media/webm/webm_parser.h"
+
+namespace media {
+
+// Parser for WebM Info element.
+class WebMInfoParser : public WebMParserClient {
+ public:
+  WebMInfoParser();
+  virtual ~WebMInfoParser();
+
+  // Parses a WebM Info element in |buf|.
+  //
+  // Returns the number of bytes parsed on success. Returns -1
+  // on error.
+  int Parse(const uint8* buf, int size);
+
+  int64 timecode_scale() const { return timecode_scale_; }
+  double duration() const { return duration_; }
+
+ private:
+  // WebMParserClient methods
+  virtual bool OnListStart(int id);
+  virtual bool OnListEnd(int id);
+  virtual bool OnUInt(int id, int64 val);
+  virtual bool OnFloat(int id, double val);
+  virtual bool OnBinary(int id, const uint8* data, int size);
+  virtual bool OnString(int id, const std::string& str);
+  virtual bool OnSimpleBlock(int track_num, int timecode, int flags,
+                             const uint8* data, int size);
+
+  int64 timecode_scale_;
+  double duration_;
+
+  DISALLOW_COPY_AND_ASSIGN(WebMInfoParser);
+};
+
+}  // namespace media
+
+#endif  // MEDIA_WEBM_WEBM_INFO_PARSER_H_
diff --git a/media/webm/webm_parser.cc b/media/webm/webm_parser.cc
new file mode 100644
index 0000000..42d826c1
--- /dev/null
+++ b/media/webm/webm_parser.cc
@@ -0,0 +1,485 @@
+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "media/webm/webm_parser.h"
+
+// This file contains code to parse WebM file elements. It was created
+// from information in the Matroska spec.
+// http://www.matroska.org/technical/specs/index.html
+
+#include <iomanip>
+
+#include "base/logging.h"
+#include "media/webm/webm_constants.h"
+
+namespace media {
+
+// Maximum depth of WebM elements. Some WebM elements are lists of
+// other elements. This limits the number levels of recursion allowed.
+static const int kMaxLevelDepth = 6;
+
+enum ElementType {
+  LIST,
+  UINT,
+  FLOAT,
+  BINARY,
+  STRING,
+  SBLOCK,
+  SKIP,
+};
+
+struct ElementIdInfo {
+  int level_;
+  ElementType type_;
+  int id_;
+};
+
+struct ListElementInfo {
+  int id_;
+  const ElementIdInfo* id_info_;
+  int id_info_size_;
+};
+
+// The following are tables indicating what IDs are valid sub-elements
+// of particular elements. If an element is encountered that doesn't
+// appear in the list, a parsing error is signalled. Some elements are
+// marked as SKIP because they are valid, but we don't care about them
+// right now.
+static const ElementIdInfo kClusterIds[] = {
+  {2, UINT, kWebMIdTimecode},
+  {2, SBLOCK, kWebMIdSimpleBlock},
+  {2, LIST, kWebMIdBlockGroup},
+};
+
+static const ElementIdInfo kInfoIds[] = {
+  {2, SKIP, kWebMIdSegmentUID},
+  {2, UINT, kWebMIdTimecodeScale},
+  {2, FLOAT, kWebMIdDuration},
+  {2, SKIP, kWebMIdDateUTC},
+  {2, SKIP, kWebMIdTitle},
+  {2, SKIP, kWebMIdMuxingApp},
+  {2, SKIP, kWebMIdWritingApp},
+};
+
+static const ElementIdInfo kTracksIds[] = {
+  {2, LIST, kWebMIdTrackEntry},
+};
+
+static const ElementIdInfo kTrackEntryIds[] = {
+  {3, UINT, kWebMIdTrackNumber},
+  {3, SKIP, kWebMIdTrackUID},
+  {3, UINT, kWebMIdTrackType},
+  {3, SKIP, kWebMIdFlagEnabled},
+  {3, SKIP, kWebMIdFlagDefault},
+  {3, SKIP, kWebMIdFlagForced},
+  {3, UINT, kWebMIdFlagLacing},
+  {3, UINT, kWebMIdDefaultDuration},
+  {3, SKIP, kWebMIdName},
+  {3, SKIP, kWebMIdLanguage},
+  {3, STRING, kWebMIdCodecID},
+  {3, BINARY, kWebMIdCodecPrivate},
+  {3, SKIP, kWebMIdCodecName},
+  {3, LIST, kWebMIdVideo},
+  {3, LIST, kWebMIdAudio},
+};
+
+static const ElementIdInfo kVideoIds[] = {
+  {4, SKIP, kWebMIdFlagInterlaced},
+  {4, SKIP, kWebMIdStereoMode},
+  {4, UINT, kWebMIdPixelWidth},
+  {4, UINT, kWebMIdPixelHeight},
+  {4, SKIP, kWebMIdPixelCropBottom},
+  {4, SKIP, kWebMIdPixelCropTop},
+  {4, SKIP, kWebMIdPixelCropLeft},
+  {4, SKIP, kWebMIdPixelCropRight},
+  {4, SKIP, kWebMIdDisplayWidth},
+  {4, SKIP, kWebMIdDisplayHeight},
+  {4, SKIP, kWebMIdDisplayUnit},
+  {4, SKIP, kWebMIdAspectRatioType},
+};
+
+static const ElementIdInfo kAudioIds[] = {
+  {4, SKIP, kWebMIdSamplingFrequency},
+  {4, SKIP, kWebMIdOutputSamplingFrequency},
+  {4, UINT, kWebMIdChannels},
+  {4, SKIP, kWebMIdBitDepth},
+};
+
+static const ElementIdInfo kClustersOnly[] = {
+  {1, LIST, kWebMIdCluster},
+};
+
+static const ListElementInfo kListElementInfo[] = {
+  { kWebMIdCluster,    kClusterIds,    sizeof(kClusterIds) },
+  { kWebMIdInfo,       kInfoIds,       sizeof(kInfoIds) },
+  { kWebMIdTracks,     kTracksIds,     sizeof(kTracksIds) },
+  { kWebMIdTrackEntry, kTrackEntryIds, sizeof(kTrackEntryIds) },
+  { kWebMIdVideo,      kVideoIds,      sizeof(kVideoIds) },
+  { kWebMIdAudio,      kAudioIds,      sizeof(kAudioIds) },
+};
+
+// Number of elements in kListElementInfo.
+const int kListElementInfoCount =
+    sizeof(kListElementInfo) / sizeof(ListElementInfo);
+
+WebMParserClient::~WebMParserClient() {}
+
+// Parses an element header id or size field. These fields are variable length
+// encoded. The first byte indicates how many bytes the field occupies.
+// |buf|  - The buffer to parse.
+// |size| - The number of bytes in |buf|
+// |max_bytes| - The maximum number of bytes the field can be. ID fields
+//               set this to 4 & element size fields set this to 8. If the
+//               first byte indicates a larger field size than this it is a
+//               parser error.
+// |mask_first_byte| - For element size fields the field length encoding bits
+//                     need to be masked off. This parameter is true for
+//                     element size fields and is false for ID field values.
+//
+// Returns: The number of bytes parsed on success. -1 on error.
+static int ParseWebMElementHeaderField(const uint8* buf, int size,
+                                       int max_bytes, bool mask_first_byte,
+                                       int64* num) {
+  DCHECK(buf);
+  DCHECK(num);
+
+  if (size <= 0)
+    return -1;
+
+  int mask = 0x80;
+  uint8 ch = buf[0];
+  int extra_bytes = -1;
+  for (int i = 0; i < max_bytes; ++i) {
+    if ((ch & mask) == mask) {
+      *num = mask_first_byte ? ch & ~mask : ch;
+      extra_bytes = i;
+      break;
+    }
+    mask >>= 1;
+  }
+
+  if ((extra_bytes == -1) || ((1 + extra_bytes) > size))
+    return -1;
+
+  int bytes_used = 1;
+
+  for (int i = 0; i < extra_bytes; ++i)
+    *num = (*num << 8) | (0xff & buf[bytes_used++]);
+
+  return bytes_used;
+}
+
+// Parses an element header & returns the ID and element size.
+//
+// Returns: The number of bytes parsed on success. -1 on error.
+// |*id| contains the element ID on success & undefined on error.
+// |*element_size| contains the element size on success & undefined on error.
+static int ParseWebMElementHeader(const uint8* buf, int size,
+                                  int* id, int64* element_size) {
+  DCHECK(buf);
+  DCHECK_GE(size, 0);
+  DCHECK(id);
+  DCHECK(element_size);
+
+  if (size == 0)
+    return 0;
+
+  int64 tmp;
+  int num_id_bytes = ParseWebMElementHeaderField(buf, size, 4, false, &tmp);
+
+  if (num_id_bytes <= 0)
+    return num_id_bytes;
+
+  *id = static_cast<int>(tmp);
+
+  int num_size_bytes = ParseWebMElementHeaderField(buf + num_id_bytes,
+                                                   size - num_id_bytes,
+                                                   8, true, &tmp);
+
+  if (num_size_bytes <= 0)
+    return num_size_bytes;
+
+  *element_size = tmp;
+  return num_id_bytes + num_size_bytes;
+}
+
+// Finds ElementIdInfo for a specific ID.
+static const ElementIdInfo* FindIdInfo(int id,
+                                       const ElementIdInfo* id_info,
+                                       int id_info_size) {
+  int count = id_info_size / sizeof(*id_info);
+  for (int i = 0; i < count; ++i) {
+    if (id == id_info[i].id_)
+      return &id_info[i];
+  }
+
+  return NULL;
+}
+
+// Finds ListElementInfo for a specific ID.
+static const ListElementInfo* FindListInfo(int id) {
+  for (int i = 0; i < kListElementInfoCount; ++i) {
+    if (id == kListElementInfo[i].id_)
+      return &kListElementInfo[i];
+  }
+
+  return NULL;
+}
+
+static int ParseSimpleBlock(const uint8* buf, int size,
+                            WebMParserClient* client) {
+  if (size < 4)
+    return -1;
+
+  // Return an error if the trackNum > 127. We just aren't
+  // going to support large track numbers right now.
+  if ((buf[0] & 0x80) != 0x80) {
+    VLOG(1) << "TrackNumber over 127 not supported";
+    return -1;
+  }
+
+  int track_num = buf[0] & 0x7f;
+  int timecode = buf[1] << 8 | buf[2];
+  int flags = buf[3] & 0xff;
+  int lacing = (flags >> 1) & 0x3;
+
+  if (lacing != 0) {
+    VLOG(1) << "Lacing " << lacing << " not supported yet.";
+    return -1;
+  }
+
+  // Sign extend negative timecode offsets.
+  if (timecode & 0x8000)
+    timecode |= (-1 << 16);
+
+  const uint8* frame_data = buf + 4;
+  int frame_size = size - (frame_data - buf);
+  if (!client->OnSimpleBlock(track_num, timecode, flags,
+                             frame_data, frame_size)) {
+    return -1;
+  }
+
+  return size;
+}
+
+static int ParseElements(const ElementIdInfo* id_info,
+                         int id_info_size,
+                         const uint8* buf, int size, int level,
+                         WebMParserClient* client);
+
+static int ParseElementList(const uint8* buf, int size,
+                            int id, int level,
+                            WebMParserClient* client) {
+  const ListElementInfo* list_info = FindListInfo(id);
+
+  if (!list_info) {
+    VLOG(1) << "Failed to find list info for ID " << std::hex << id;
+    return -1;
+  }
+
+  if (!client->OnListStart(id))
+    return -1;
+
+  int res = ParseElements(list_info->id_info_,
+                          list_info->id_info_size_,
+                          buf, size,
+                          level + 1,
+                          client);
+
+  if (res < 0)
+    return -1;
+
+  if (!client->OnListEnd(id))
+    return -1;
+
+  DCHECK_EQ(res, size);
+  return res;
+}
+
+static int ParseUInt(const uint8* buf, int size, int id,
+                     WebMParserClient* client) {
+  if ((size <= 0) || (size > 8))
+    return -1;
+
+  // Read in the big-endian integer.
+  int64 value = 0;
+  for (int i = 0; i < size; ++i)
+    value = (value << 8) | buf[i];
+
+  if (!client->OnUInt(id, value))
+    return -1;
+
+  return size;
+}
+
+static int ParseFloat(const uint8* buf, int size, int id,
+                      WebMParserClient* client) {
+
+  if ((size != 4) && (size != 8))
+    return -1;
+
+  double value = -1;
+
+  // Read the bytes from big-endian form into a native endian integer.
+  int64 tmp = 0;
+  for (int i = 0; i < size; ++i)
+    tmp = (tmp << 8) | buf[i];
+
+  // Use a union to convert the integer bit pattern into a floating point
+  // number.
+  if (size == 4) {
+    union {
+      int32 src;
+      float dst;
+    } tmp2;
+    tmp2.src = static_cast<int32>(tmp);
+    value = tmp2.dst;
+  } else if (size == 8) {
+    union {
+      int64 src;
+      double dst;
+    } tmp2;
+    tmp2.src = tmp;
+    value = tmp2.dst;
+  } else {
+    return -1;
+  }
+
+  if (!client->OnFloat(id, value))
+    return -1;
+
+  return size;
+}
+
+static int ParseElements(const ElementIdInfo* id_info,
+                         int id_info_size,
+                         const uint8* buf, int size, int level,
+                         WebMParserClient* client) {
+  DCHECK_GE(id_info_size, 0);
+  DCHECK_GE(size, 0);
+  DCHECK_GE(level, 0);
+
+  const uint8* cur = buf;
+  int cur_size = size;
+  int used = 0;
+
+  if (level > kMaxLevelDepth)
+    return -1;
+
+  while (cur_size > 0) {
+    int id;
+    int64 element_size;
+    int res = ParseWebMElementHeader(cur, cur_size, &id, &element_size);
+
+    if (res < 0)
+      return res;
+
+    if (res == 0)
+      break;
+
+    cur += res;
+    cur_size -= res;
+    used += res;
+
+    // Check to see if the element is larger than the remaining data.
+    if (element_size > cur_size)
+      return -1;
+
+    const ElementIdInfo* info = FindIdInfo(id, id_info, id_info_size);
+
+    if (info == NULL) {
+      VLOG(1) << "No info for ID " << std::hex << id;
+
+      // TODO(acolwell): Change this to return -1 after the API has solidified.
+      // We don't want to allow elements we don't recognize.
+      cur += element_size;
+      cur_size -= element_size;
+      used += element_size;
+      continue;
+    }
+
+    if (info->level_ != level) {
+      VLOG(1) << "ID " << std::hex << id << std::dec << " at level "
+              << level << " instead of " << info->level_;
+      return -1;
+    }
+
+    switch(info->type_) {
+      case SBLOCK:
+        if (ParseSimpleBlock(cur, element_size, client) <= 0)
+          return -1;
+        break;
+      case LIST:
+        if (ParseElementList(cur, element_size, id, level, client) < 0)
+          return -1;
+        break;
+      case UINT:
+        if (ParseUInt(cur, element_size, id, client) <= 0)
+          return -1;
+        break;
+      case FLOAT:
+        if (ParseFloat(cur, element_size, id, client) <= 0)
+          return -1;
+        break;
+      case BINARY:
+        if (!client->OnBinary(id, cur, element_size))
+          return -1;
+        break;
+      case STRING:
+        if (!client->OnString(id,
+                              std::string(reinterpret_cast<const char*>(cur),
+                                          element_size)))
+          return -1;
+        break;
+      case SKIP:
+        // Do nothing.
+        break;
+      default:
+        VLOG(1) << "Unhandled id type " << info->type_;
+        return -1;
+    };
+
+    cur += element_size;
+    cur_size -= element_size;
+    used += element_size;
+  }
+
+  return used;
+}
+
+// Parses a single list element that matches |id|. This method fails if the
+// buffer points to an element that does not match |id|.
+int WebMParseListElement(const uint8* buf, int size, int id,
+                         int level, WebMParserClient* client) {
+  if (size == 0)
+    return -1;
+
+  const uint8* cur = buf;
+  int cur_size = size;
+
+  int element_id = 0;
+  int64 element_size = 0;
+  int res = ParseWebMElementHeader(cur, cur_size, &element_id, &element_size);
+
+  if (res <= 0)
+    return res;
+
+  cur += res;
+  cur_size -= res;
+
+  if (element_id != id || element_size > cur_size)
+    return -1;
+
+  res = ParseElementList(cur, element_size, element_id, level, client);
+
+  if (res < 0)
+    return -1;
+
+  cur += res;
+  cur_size -= res;
+
+  return size - cur_size;
+}
+
+}  // namespace media
diff --git a/media/webm/webm_parser.h b/media/webm/webm_parser.h
new file mode 100644
index 0000000..0716b80
--- /dev/null
+++ b/media/webm/webm_parser.h
@@ -0,0 +1,46 @@
+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef MEDIA_WEBM_WEBM_PARSER_H_
+#define MEDIA_WEBM_WEBM_PARSER_H_
+
+#include <string>
+
+#include "base/basictypes.h"
+
+namespace media {
+
+// Interface for receiving WebM parser events.
+//
+// Each method is called when an element of the specified type is parsed.
+// The ID of the element that was parsed is given along with the value
+// stored in the element. List elements generate calls at the start and
+// end of the list. Any pointers passed to these methods are only guaranteed
+// to be valid for the life of that call. Each method returns a bool that
+// indicates whether the parsed data is valid. If false is returned
+// then the parse is immediately terminated and an error is reported by the
+// parser.
+class WebMParserClient {
+ public:
+  virtual ~WebMParserClient();
+
+  virtual bool OnListStart(int id) = 0;
+  virtual bool OnListEnd(int id) = 0;
+  virtual bool OnUInt(int id, int64 val) = 0;
+  virtual bool OnFloat(int id, double val) = 0;
+  virtual bool OnBinary(int id, const uint8* data, int size) = 0;
+  virtual bool OnString(int id, const std::string& str) = 0;
+  virtual bool OnSimpleBlock(int track_num, int timecode,
+                             int flags,
+                             const uint8* data, int size) = 0;
+};
+
+// Parses a single list element that matches |id|. This method fails if the
+// buffer points to an element that does not match |id|.
+int WebMParseListElement(const uint8* buf, int size, int id,
+                         int level, WebMParserClient* client);
+
+}  // namespace media
+
+#endif  // MEDIA_WEBM_WEBM_PARSER_H_
diff --git a/media/webm/webm_tracks_parser.cc b/media/webm/webm_tracks_parser.cc
new file mode 100644
index 0000000..29b4f33
--- /dev/null
+++ b/media/webm/webm_tracks_parser.cc
@@ -0,0 +1,123 @@
+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "media/webm/webm_tracks_parser.h"
+
+#include "base/logging.h"
+#include "media/webm/webm_constants.h"
+
+namespace media {
+
+WebMTracksParser::WebMTracksParser(int64 timecode_scale)
+    : timecode_scale_(timecode_scale),
+      track_type_(-1),
+      track_num_(-1),
+      track_default_duration_(-1),
+      audio_track_num_(-1),
+      audio_default_duration_(base::TimeDelta::FromMicroseconds(-1)),
+      video_track_num_(-1),
+      video_default_duration_(base::TimeDelta::FromMicroseconds(-1)) {
+}
+
+WebMTracksParser::~WebMTracksParser() {}
+
+int WebMTracksParser::Parse(const uint8* buf, int size) {
+  return WebMParseListElement(buf, size, kWebMIdTracks, 1, this);
+}
+
+
+bool WebMTracksParser::OnListStart(int id) {
+  if (id == kWebMIdTrackEntry) {
+    track_type_ = -1;
+    track_num_ = -1;
+    track_default_duration_ = -1;
+  }
+
+  return true;
+}
+
+bool WebMTracksParser::OnListEnd(int id) {
+  if (id == kWebMIdTrackEntry) {
+    if (track_type_ == -1 || track_num_ == -1) {
+      VLOG(1) << "Missing TrackEntry data"
+              << " TrackType " << track_type_
+              << " TrackNum " << track_num_;
+      return false;
+    }
+
+    // Convert nanoseconds to base::TimeDelta.
+    base::TimeDelta default_duration = base::TimeDelta::FromMicroseconds(
+        track_default_duration_ / 1000.0);
+
+    if (track_type_ == kWebMTrackTypeVideo) {
+      video_track_num_ = track_num_;
+      video_default_duration_ = default_duration;
+    } else if (track_type_ == kWebMTrackTypeAudio) {
+      audio_track_num_ = track_num_;
+      audio_default_duration_ = default_duration;
+    } else {
+      VLOG(1) << "Unexpected TrackType " << track_type_;
+      return false;
+    }
+
+    track_type_ = -1;
+    track_num_ = -1;
+  }
+
+  return true;
+}
+
+bool WebMTracksParser::OnUInt(int id, int64 val) {
+  int64* dst = NULL;
+
+  switch (id) {
+    case kWebMIdTrackNumber:
+      dst = &track_num_;
+      break;
+    case kWebMIdTrackType:
+      dst = &track_type_;
+      break;
+    case  kWebMIdDefaultDuration:
+      dst = &track_default_duration_;
+      break;
+    default:
+      return true;
+  }
+
+  if (*dst != -1) {
+    VLOG(1) << "Multiple values for id " << std::hex << id << " specified";
+    return false;
+  }
+
+  *dst = val;
+  return true;
+}
+
+bool WebMTracksParser::OnFloat(int id, double val) {
+  VLOG(1) << "Unexpected float for id" << std::hex << id;
+  return false;
+}
+
+bool WebMTracksParser::OnBinary(int id, const uint8* data, int size) {
+  return true;
+}
+
+bool WebMTracksParser::OnString(int id, const std::string& str) {
+  if (id != kWebMIdCodecID)
+    return false;
+
+  if (str != "A_VORBIS" && str != "V_VP8") {
+    VLOG(1) << "Unexpected CodecID " << str;
+    return false;
+  }
+
+  return true;
+}
+
+bool WebMTracksParser::OnSimpleBlock(int track_num, int timecode, int flags,
+                                     const uint8* data, int size) {
+  return false;
+}
+
+}  // namespace media
diff --git a/media/webm/webm_tracks_parser.h b/media/webm/webm_tracks_parser.h
new file mode 100644
index 0000000..a1d0081
--- /dev/null
+++ b/media/webm/webm_tracks_parser.h
@@ -0,0 +1,61 @@
+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef MEDIA_WEBM_WEBM_TRACKS_PARSER_H_
+#define MEDIA_WEBM_WEBM_TRACKS_PARSER_H_
+
+#include "media/webm/webm_parser.h"
+
+#include "base/time.h"
+
+namespace media {
+
+// Parser for WebM Tracks element.
+class WebMTracksParser : public WebMParserClient {
+ public:
+  WebMTracksParser(int64 timecode_scale);
+  virtual ~WebMTracksParser();
+
+  // Parses a WebM Tracks element in |buf|.
+  //
+  // Returns the number of bytes parsed on success. Returns -1
+  // on error.
+  int Parse(const uint8* buf, int size);
+
+  int64 audio_track_num() const { return audio_track_num_; }
+  base::TimeDelta audio_default_duration() const {
+    return audio_default_duration_;
+  }
+
+  int64 video_track_num() const { return video_track_num_; }
+  base::TimeDelta video_default_duration() const {
+    return video_default_duration_;
+  }
+
+ private:
+  // WebMParserClient methods
+  virtual bool OnListStart(int id);
+  virtual bool OnListEnd(int id);
+  virtual bool OnUInt(int id, int64 val);
+  virtual bool OnFloat(int id, double val);
+  virtual bool OnBinary(int id, const uint8* data, int size);
+  virtual bool OnString(int id, const std::string& str);
+  virtual bool OnSimpleBlock(int track_num, int timecode, int flags,
+                             const uint8* data, int size);
+  int64 timecode_scale_;
+
+  int64 track_type_;
+  int64 track_num_;
+  int64 track_default_duration_;
+  int64 audio_track_num_;
+  base::TimeDelta audio_default_duration_;
+  int64 video_track_num_;
+  base::TimeDelta video_default_duration_;
+
+  DISALLOW_IMPLICIT_CONSTRUCTORS(WebMTracksParser);
+};
+
+}  // namespace media
+
+#endif  // MEDIA_WEBM_WEBM_TRACKS_PARSER_H_