[WebMIDI] Introduce UsbMidi{Input, Output}Stream.

UsbMidiInputStream converts USB-MIDI messages to MIDI messages.
UsbMidiOutputStream converts MIDI MIDI messages to USB-MIDI messages.

BUG=303596
R=toyoshim@chromium.org

Review URL: https://codereview.chromium.org/107513012

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@246277 0039d316-1c4b-4281-b951-d872f2087c98

10 files changed, 918 insertions, 7 deletions

diff --git a/content/browser/renderer_host/media/midi_host.cc b/content/browser/renderer_host/media/midi_host.cc
index 2eb5ec6..765ebc1 100644
--- a/content/browser/renderer_host/media/midi_host.cc
+++ b/content/browser/renderer_host/media/midi_host.cc
@@ -35,9 +35,6 @@ const size_t kMaxInFlightBytes = 10 * 1024 * 1024;  // 10 MB.
 // how many bytes will be sent before reporting back to the renderer.
 const size_t kAcknowledgementThresholdBytes = 1024 * 1024;  // 1 MB.
 
-const uint8 kSysExMessage = 0xf0;
-const uint8 kEndOfSysExMessage = 0xf7;
-
 bool IsDataByte(uint8 data) {
   return (data & 0x80) == 0;
 }
@@ -48,6 +45,9 @@ bool IsSystemRealTimeMessage(uint8 data) {
 
 }  // namespace
 
+using media::kSysExByte;
+using media::kEndOfSysExByte;
+
 MIDIHost::MIDIHost(int renderer_process_id, media::MIDIManager* midi_manager)
     : renderer_process_id_(renderer_process_id),
       has_sys_ex_permission_(false),
@@ -119,7 +119,7 @@ void MIDIHost::OnSendData(uint32 port,
   // in JavaScript. The actual permission check for security purposes
   // happens here in the browser process.
   if (!has_sys_ex_permission_ &&
-      (std::find(data.begin(), data.end(), kSysExMessage) != data.end())) {
+      std::find(data.begin(), data.end(), kSysExByte) != data.end()) {
     RecordAction(base::UserMetricsAction("BadMessageTerminate_MIDI"));
     BadMessageReceived();
     return;
@@ -162,7 +162,7 @@ void MIDIHost::ReceiveMIDIData(
     // MIDI devices may send a system exclusive messages even if the renderer
     // doesn't have a permission to receive it. Don't kill the renderer as
     // OnSendData() does.
-    if (message[0] == kSysExMessage && !has_sys_ex_permission_)
+    if (message[0] == kSysExByte && !has_sys_ex_permission_)
       continue;
 
     // Send to the renderer.
@@ -204,13 +204,13 @@ bool MIDIHost::IsValidWebMIDIData(const std::vector<uint8>& data) {
       continue;  // Found data byte as expected.
     }
     if (in_sysex) {
-      if (data[i] == kEndOfSysExMessage)
+      if (data[i] == kEndOfSysExByte)
         in_sysex = false;
       else if (!IsDataByte(current))
         return false;  // Error: |current| should have been data byte.
       continue;  // Found data byte as expected.
     }
-    if (current == kSysExMessage) {
+    if (current == kSysExByte) {
       in_sysex = true;
       continue;  // Found SysEX
     }
diff --git a/media/media.gyp b/media/media.gyp
index a983499..6e5d89b 100644
--- a/media/media.gyp
+++ b/media/media.gyp
@@ -427,7 +427,12 @@
         'midi/midi_port_info.h',
         'midi/usb_midi_descriptor_parser.cc',
         'midi/usb_midi_descriptor_parser.h',
+        'midi/usb_midi_device.h',
+        'midi/usb_midi_input_stream.cc',
+        'midi/usb_midi_input_stream.h',
         'midi/usb_midi_jack.h',
+        'midi/usb_midi_output_stream.cc',
+        'midi/usb_midi_output_stream.h',
         'video/capture/android/video_capture_device_android.cc',
         'video/capture/android/video_capture_device_android.h',
         'video/capture/fake_video_capture_device.cc',
@@ -1019,6 +1024,8 @@
         'midi/midi_message_queue_unittest.cc',
         'midi/midi_message_util_unittest.cc',
         'midi/usb_midi_descriptor_parser_unittest.cc',
+        'midi/usb_midi_input_stream_unittest.cc',
+        'midi/usb_midi_output_stream_unittest.cc',
         'video/capture/video_capture_device_unittest.cc',
         'webm/cluster_builder.cc',
         'webm/cluster_builder.h',
diff --git a/media/midi/midi_message_util.h b/media/midi/midi_message_util.h
index 1dc6d3c..b40d814 100644
--- a/media/midi/midi_message_util.h
+++ b/media/midi/midi_message_util.h
@@ -20,6 +20,14 @@ namespace media {
 // - the End of System Exclusive message.
 MEDIA_EXPORT size_t GetMIDIMessageLength(uint8 status_byte);
 
+const uint8 kSysExByte = 0xf0;
+const uint8 kEndOfSysExByte = 0xf7;
+
+const uint8 kSysMessageBitMask = 0xf0;
+const uint8 kSysMessageBitPattern = 0xf0;
+const uint8 kSysRTMessageBitMask = 0xf8;
+const uint8 kSysRTMessageBitPattern = 0xf8;
+
 }  // namespace media
 
 #endif  // MEDIA_MIDI_MIDI_MESSAGE_UTIL_H_
diff --git a/media/midi/usb_midi_device.h b/media/midi/usb_midi_device.h
new file mode 100644
index 0000000..3f29d64
--- /dev/null
+++ b/media/midi/usb_midi_device.h
@@ -0,0 +1,31 @@
+// Copyright 2014 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_MIDI_USB_MIDI_DEVICE_H_
+#define MEDIA_MIDI_USB_MIDI_DEVICE_H_
+
+#include <vector>
+
+#include "base/basictypes.h"
+#include "media/base/media_export.h"
+
+namespace media {
+
+// UsbMidiDevice represents a USB-MIDI device.
+// This is an interface class and each platform-dependent implementation class
+// will be a derived class.
+class MEDIA_EXPORT UsbMidiDevice {
+ public:
+  virtual ~UsbMidiDevice() {}
+
+  // Returns the descriptor of this device.
+  virtual std::vector<uint8> GetDescriptor() = 0;
+
+  // Sends |data| to the given USB endpoint of this device.
+  virtual void Send(int endpoint_number, const std::vector<uint8>& data) = 0;
+};
+
+}  // namespace media
+
+#endif  // MEDIA_MIDI_USB_MIDI_DEVICE_H_
diff --git a/media/midi/usb_midi_input_stream.cc b/media/midi/usb_midi_input_stream.cc
new file mode 100644
index 0000000..f68436c
--- /dev/null
+++ b/media/midi/usb_midi_input_stream.cc
@@ -0,0 +1,92 @@
+// Copyright 2014 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/midi/usb_midi_input_stream.h"
+
+#include <string.h>
+#include <map>
+#include <vector>
+
+#include "base/logging.h"
+#include "media/midi/usb_midi_device.h"
+#include "media/midi/usb_midi_jack.h"
+
+namespace media {
+
+UsbMidiInputStream::JackUniqueKey::JackUniqueKey(UsbMidiDevice* device,
+                                                 int endpoint_number,
+                                                 int cable_number)
+    : device(device),
+      endpoint_number(endpoint_number),
+      cable_number(cable_number) {}
+
+bool UsbMidiInputStream::JackUniqueKey::operator==(
+    const JackUniqueKey& that) const {
+  return device == that.device &&
+      endpoint_number == that.endpoint_number &&
+      cable_number == that.cable_number;
+}
+
+bool UsbMidiInputStream::JackUniqueKey::operator<(
+    const JackUniqueKey& that) const {
+  if (device != that.device)
+    return device < that.device;
+  if (endpoint_number != that.endpoint_number)
+    return endpoint_number < that.endpoint_number;
+  return cable_number < that.cable_number;
+}
+
+UsbMidiInputStream::UsbMidiInputStream(const std::vector<UsbMidiJack>& jacks,
+                                       Delegate* delegate)
+    : delegate_(delegate) {
+  for (size_t i = 0; i < jacks.size(); ++i) {
+    jack_dictionary_.insert(
+        std::make_pair(JackUniqueKey(jacks[i].device,
+                                     jacks[i].endpoint_number(),
+                                     jacks[i].cable_number),
+                       i));
+  }
+}
+
+UsbMidiInputStream::~UsbMidiInputStream() {}
+
+void UsbMidiInputStream::OnReceivedData(UsbMidiDevice* device,
+                                        int endpoint_number,
+                                        const uint8* data,
+                                        size_t size,
+                                        double timestamp) {
+  DCHECK_EQ(0u, size % kPacketSize);
+  size_t current = 0;
+  while (current + kPacketSize <= size) {
+    ProcessOnePacket(device, endpoint_number, &data[current], timestamp);
+    current += kPacketSize;
+  }
+}
+
+void UsbMidiInputStream::ProcessOnePacket(UsbMidiDevice* device,
+                                          int endpoint_number,
+                                          const uint8* packet,
+                                          double timestamp) {
+  // The first 4 bytes of the packet is accessible here.
+  uint8 code_index = packet[0] & 0x0f;
+  uint8 cable_number = packet[0] >> 4;
+  const size_t packet_size_table[16] = {
+    0, 0, 2, 3, 3, 1, 2, 3, 3, 3, 3, 3, 2, 2, 3, 1,
+  };
+  size_t packet_size = packet_size_table[code_index];
+  if (packet_size == 0) {
+    // These CINs are reserved. Ignore them.
+    DVLOG(1) << "code index number (" << code_index << ") arrives "
+             << "but it is reserved.";
+    return;
+  }
+  std::map<JackUniqueKey, size_t>::const_iterator it =
+      jack_dictionary_.find(JackUniqueKey(device,
+                                          endpoint_number,
+                                          cable_number));
+  if (it != jack_dictionary_.end())
+    delegate_->OnReceivedData(it->second, &packet[1], packet_size, timestamp);
+}
+
+}  // namespace media
diff --git a/media/midi/usb_midi_input_stream.h b/media/midi/usb_midi_input_stream.h
new file mode 100644
index 0000000..70ed306
--- /dev/null
+++ b/media/midi/usb_midi_input_stream.h
@@ -0,0 +1,80 @@
+// Copyright 2014 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_MIDI_USB_MIDI_INPUT_STREAM_H_
+#define MEDIA_MIDI_USB_MIDI_INPUT_STREAM_H_
+
+#include <map>
+#include <vector>
+
+#include "base/basictypes.h"
+#include "base/containers/hash_tables.h"
+#include "media/base/media_export.h"
+#include "media/midi/usb_midi_jack.h"
+
+namespace media {
+
+class UsbMidiDevice;
+
+// UsbMidiInputStream converts USB-MIDI data to MIDI data.
+// See "USB Device Class Definition for MIDI Devices" Release 1.0,
+// Section 4 "USB-MIDI Event Packets" for details.
+class MEDIA_EXPORT UsbMidiInputStream {
+ public:
+  class Delegate {
+   public:
+    virtual ~Delegate() {}
+    // This function is called when some data arrives to a USB-MIDI jack.
+    // An input USB-MIDI jack corresponds to an input MIDIPortInfo.
+    virtual void OnReceivedData(size_t jack_index,
+                                const uint8* data,
+                                size_t size,
+                                double timestamp) = 0;
+  };
+
+  UsbMidiInputStream(const std::vector<UsbMidiJack>& jacks,
+                     Delegate* delegate);
+  ~UsbMidiInputStream();
+
+  // This function should be called when some data arrives to a USB-MIDI
+  // endpoint. This function converts the data to MIDI data and call
+  // |delegate->OnReceivedData| with it.
+  // |size| must be a multiple of |kPacketSize|.
+  void OnReceivedData(UsbMidiDevice* device,
+                      int endpoint_number,
+                      const uint8* data,
+                      size_t size,
+                      double timestamp);
+
+ private:
+  static const size_t kPacketSize = 4;
+  struct JackUniqueKey {
+    JackUniqueKey(UsbMidiDevice* device, int endpoint_number, int cable_number);
+    bool operator==(const JackUniqueKey& that) const;
+    bool operator<(const JackUniqueKey& that) const;
+
+    UsbMidiDevice* device;
+    int endpoint_number;
+    int cable_number;
+  };
+
+  // Processes a USB-MIDI Event Packet.
+  // The first |kPacketSize| bytes of |packet| must be accessible.
+  void ProcessOnePacket(UsbMidiDevice* device,
+                        int endpoint_number,
+                        const uint8* packet,
+                        double timestamp);
+
+  // A map from UsbMidiJack to its index in |jacks_|.
+  std::map<JackUniqueKey, size_t> jack_dictionary_;
+
+  // Not owned
+  Delegate* delegate_;
+
+  DISALLOW_COPY_AND_ASSIGN(UsbMidiInputStream);
+};
+
+}  // namespace media
+
+#endif  // MEDIA_MIDI_USB_MIDI_INPUT_STREAM_H_
diff --git a/media/midi/usb_midi_input_stream_unittest.cc b/media/midi/usb_midi_input_stream_unittest.cc
new file mode 100644
index 0000000..589f490
--- /dev/null
+++ b/media/midi/usb_midi_input_stream_unittest.cc
@@ -0,0 +1,175 @@
+// Copyright 2014 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/midi/usb_midi_input_stream.h"
+
+#include <string>
+#include <vector>
+
+#include "base/memory/scoped_ptr.h"
+#include "base/strings/stringprintf.h"
+#include "media/midi/usb_midi_device.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace media {
+
+namespace {
+
+class TestUsbMidiDevice : public UsbMidiDevice {
+ public:
+  TestUsbMidiDevice() {}
+  virtual ~TestUsbMidiDevice() {}
+  virtual std::vector<uint8> GetDescriptor() OVERRIDE {
+    return std::vector<uint8>();
+  }
+  virtual void Send(int endpoint_number,
+                    const std::vector<uint8>& data) OVERRIDE {}
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(TestUsbMidiDevice);
+};
+
+class MockDelegate : public UsbMidiInputStream::Delegate {
+ public:
+  MockDelegate() {}
+  virtual ~MockDelegate() {}
+  virtual void OnReceivedData(size_t jack_index,
+                              const uint8* data,
+                              size_t size,
+                              double timestamp) OVERRIDE {
+    for (size_t i = 0; i < size; ++i)
+      received_data_ += base::StringPrintf("0x%02x ", data[i]);
+    received_data_ += "\n";
+  }
+
+  const std::string& received_data() const { return received_data_; }
+
+ private:
+  std::string received_data_;
+  DISALLOW_COPY_AND_ASSIGN(MockDelegate);
+};
+
+class UsbMidiInputStreamTest : public ::testing::Test {
+ protected:
+  UsbMidiInputStreamTest() {
+    std::vector<UsbMidiJack> jacks;
+
+    jacks.push_back(UsbMidiJack(&device1_,
+                                84,  // jack_id
+                                4,  // cable_number
+                                135));  // endpoint_address
+    jacks.push_back(UsbMidiJack(&device2_,
+                                85,
+                                5,
+                                137));
+    jacks.push_back(UsbMidiJack(&device2_,
+                                84,
+                                4,
+                                135));
+    jacks.push_back(UsbMidiJack(&device1_,
+                                85,
+                                5,
+                                135));
+
+    stream_.reset(new UsbMidiInputStream(jacks, &delegate_));
+  }
+
+  TestUsbMidiDevice device1_;
+  TestUsbMidiDevice device2_;
+  MockDelegate delegate_;
+  scoped_ptr<UsbMidiInputStream> stream_;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(UsbMidiInputStreamTest);
+};
+
+TEST_F(UsbMidiInputStreamTest, UnknownMessage) {
+  uint8 data[] = {
+    0x40, 0xff, 0xff, 0xff,
+    0x41, 0xff, 0xff, 0xff,
+  };
+
+  stream_->OnReceivedData(&device1_, 7, data, arraysize(data), 0);
+  EXPECT_EQ("", delegate_.received_data());
+}
+
+TEST_F(UsbMidiInputStreamTest, SystemCommonMessage) {
+  uint8 data[] = {
+    0x45, 0xf8, 0x00, 0x00,
+    0x42, 0xf3, 0x22, 0x00,
+    0x43, 0xf2, 0x33, 0x44,
+  };
+
+  stream_->OnReceivedData(&device1_, 7, data, arraysize(data), 0);
+  EXPECT_EQ("0xf8 \n"
+            "0xf3 0x22 \n"
+            "0xf2 0x33 0x44 \n", delegate_.received_data());
+}
+
+TEST_F(UsbMidiInputStreamTest, SystemExclusiveMessage) {
+  uint8 data[] = {
+    0x44, 0xf0, 0x11, 0x22,
+    0x45, 0xf7, 0x00, 0x00,
+    0x46, 0xf0, 0xf7, 0x00,
+    0x47, 0xf0, 0x33, 0xf7,
+  };
+
+  stream_->OnReceivedData(&device1_, 7, data, arraysize(data), 0);
+  EXPECT_EQ("0xf0 0x11 0x22 \n"
+            "0xf7 \n"
+            "0xf0 0xf7 \n"
+            "0xf0 0x33 0xf7 \n", delegate_.received_data());
+}
+
+TEST_F(UsbMidiInputStreamTest, ChannelMessage) {
+  uint8 data[] = {
+    0x48, 0x80, 0x11, 0x22,
+    0x49, 0x90, 0x33, 0x44,
+    0x4a, 0xa0, 0x55, 0x66,
+    0x4b, 0xb0, 0x77, 0x88,
+    0x4c, 0xc0, 0x99, 0x00,
+    0x4d, 0xd0, 0xaa, 0x00,
+    0x4e, 0xe0, 0xbb, 0xcc,
+  };
+
+  stream_->OnReceivedData(&device1_, 7, data, arraysize(data), 0);
+  EXPECT_EQ("0x80 0x11 0x22 \n"
+            "0x90 0x33 0x44 \n"
+            "0xa0 0x55 0x66 \n"
+            "0xb0 0x77 0x88 \n"
+            "0xc0 0x99 \n"
+            "0xd0 0xaa \n"
+            "0xe0 0xbb 0xcc \n", delegate_.received_data());
+}
+
+TEST_F(UsbMidiInputStreamTest, SingleByteMessage) {
+  uint8 data[] = {
+    0x4f, 0xf8, 0x00, 0x00,
+  };
+
+  stream_->OnReceivedData(&device1_, 7, data, arraysize(data), 0);
+  EXPECT_EQ("0xf8 \n", delegate_.received_data());
+}
+
+TEST_F(UsbMidiInputStreamTest, DispatchForMultipleCables) {
+  uint8 data[] = {
+    0x4f, 0xf8, 0x00, 0x00,
+    0x5f, 0xfa, 0x00, 0x00,
+    0x6f, 0xfb, 0x00, 0x00,
+  };
+
+  stream_->OnReceivedData(&device1_, 7, data, arraysize(data), 99);
+  EXPECT_EQ("0xf8 \n0xfa \n", delegate_.received_data());
+}
+
+TEST_F(UsbMidiInputStreamTest, DispatchForDevice2) {
+  uint8 data[] = { 0x4f, 0xf8, 0x00, 0x00 };
+
+  stream_->OnReceivedData(&device2_, 7, data, arraysize(data), 99);
+  EXPECT_EQ("0xf8 \n", delegate_.received_data());
+}
+
+}  // namespace
+
+}  // namespace media
diff --git a/media/midi/usb_midi_output_stream.cc b/media/midi/usb_midi_output_stream.cc
new file mode 100644
index 0000000..1aef282
--- /dev/null
+++ b/media/midi/usb_midi_output_stream.cc
@@ -0,0 +1,187 @@
+// Copyright 2014 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/midi/usb_midi_output_stream.h"
+
+#include "base/logging.h"
+#include "media/midi/midi_message_util.h"
+#include "media/midi/usb_midi_device.h"
+
+namespace media {
+
+UsbMidiOutputStream::UsbMidiOutputStream(const UsbMidiJack& jack)
+    : jack_(jack), pending_size_(0), is_sending_sysex_(false) {}
+
+void UsbMidiOutputStream::Send(const std::vector<uint8>& data) {
+  // To prevent link errors caused by DCHECK_*.
+  const size_t kPacketContentSize = UsbMidiOutputStream::kPacketContentSize;
+  DCHECK_LT(jack_.cable_number, 16u);
+
+  std::vector<uint8> data_to_send;
+  size_t current = 0;
+  size_t size = GetSize(data);
+  while (current < size) {
+    uint8 first_byte = Get(data, current);
+    if (first_byte == kSysExByte || is_sending_sysex_) {
+      // System Exclusive messages
+      if (!PushSysExMessage(data, &current, &data_to_send))
+        break;
+    } else if ((first_byte & kSysMessageBitMask) == kSysMessageBitPattern) {
+      if (first_byte & 0x08) {
+        // System Real-Time messages
+        PushSysRTMessage(data, &current, &data_to_send);
+      } else {
+        // System Common messages
+        if (!PushSysCommonMessage(data, &current, &data_to_send))
+          break;
+      }
+    } else if (first_byte & 0x80) {
+      if (!PushChannelMessage(data, &current, &data_to_send))
+        break;
+    } else {
+      // Unknown messages
+      DVLOG(1) << "Unknown byte: " << static_cast<unsigned int>(first_byte);
+      ++current;
+    }
+  }
+
+  if (data_to_send.size() > 0)
+    jack_.device->Send(jack_.endpoint_number(), data_to_send);
+
+  DCHECK_LE(current, size);
+  DCHECK_LE(size - current, kPacketContentSize);
+  // Note that this can be a self-copying and the iteration order is important.
+  for (size_t i = current; i < size; ++i)
+    pending_data_[i - current] = Get(data, i);
+  pending_size_ = size - current;
+}
+
+size_t UsbMidiOutputStream::GetSize(const std::vector<uint8>& data) const {
+  return data.size() + pending_size_;
+}
+
+uint8_t UsbMidiOutputStream::Get(const std::vector<uint8>& data,
+                               size_t index) const {
+  DCHECK_LT(index, GetSize(data));
+  if (index < pending_size_)
+    return pending_data_[index];
+  return data[index - pending_size_];
+}
+
+bool UsbMidiOutputStream::PushSysExMessage(const std::vector<uint8>& data,
+                                           size_t* current,
+                                           std::vector<uint8>* data_to_send) {
+  size_t index = *current;
+  size_t message_size = 0;
+  const size_t kMessageSizeMax = 3;
+  uint8 message[kMessageSizeMax] = {};
+
+  while (index < GetSize(data)) {
+    if (message_size == kMessageSizeMax) {
+      // We can't find the end-of-message mark in the three bytes.
+      *current = index;
+      data_to_send->push_back((jack_.cable_number << 4) | 0x4);
+      data_to_send->insert(data_to_send->end(),
+                           message,
+                           message + arraysize(message));
+      is_sending_sysex_ = true;
+      return true;
+    }
+    uint8 byte = Get(data, index);
+    if ((byte & kSysRTMessageBitMask) == kSysRTMessageBitPattern) {
+      // System Real-Time messages interleaved in a SysEx message
+      PushSysRTMessage(data, &index, data_to_send);
+      continue;
+    }
+
+    message[message_size] = byte;
+    ++message_size;
+    if (byte == kEndOfSysExByte) {
+      uint8 code_index = message_size + 0x4;
+      DCHECK(code_index == 0x5 || code_index == 0x6 || code_index == 0x7);
+      data_to_send->push_back((jack_.cable_number << 4) | code_index);
+      data_to_send->insert(data_to_send->end(),
+                           message,
+                           message + arraysize(message));
+      *current = index + 1;
+      is_sending_sysex_ = false;
+      return true;
+    }
+    ++index;
+  }
+  return false;
+}
+
+bool UsbMidiOutputStream::PushSysCommonMessage(
+    const std::vector<uint8>& data,
+    size_t* current,
+    std::vector<uint8>* data_to_send) {
+  size_t index = *current;
+  uint8 first_byte = Get(data, index);
+  DCHECK_LE(0xf1, first_byte);
+  DCHECK_LE(first_byte, 0xf7);
+  const size_t message_size_table[8] = {
+    0, 2, 3, 2, 1, 1, 1, 0,
+  };
+  size_t message_size = message_size_table[first_byte & 0x0f];
+  DCHECK_NE(0u, message_size);
+  DCHECK_LE(message_size, 3u);
+
+  if (GetSize(data) < index + message_size) {
+    // The message is incomplete.
+    return false;
+  }
+
+  uint8 code_index = message_size == 1 ? 0x5 : static_cast<uint8>(message_size);
+  data_to_send->push_back((jack_.cable_number << 4) | code_index);
+  for (size_t i = index; i < index + 3; ++i)
+    data_to_send->push_back(i < index + message_size ? Get(data, i) : 0);
+  *current += message_size;
+  return true;
+}
+
+void UsbMidiOutputStream::PushSysRTMessage(const std::vector<uint8>& data,
+                                           size_t* current,
+                                           std::vector<uint8>* data_to_send) {
+  size_t index = *current;
+  uint8 first_byte = Get(data, index);
+  DCHECK_LE(0xf8, first_byte);
+  DCHECK_LE(first_byte, 0xff);
+
+  data_to_send->push_back((jack_.cable_number << 4) | 0x5);
+  data_to_send->push_back(first_byte);
+  data_to_send->push_back(0);
+  data_to_send->push_back(0);
+  *current += 1;
+}
+
+bool UsbMidiOutputStream::PushChannelMessage(const std::vector<uint8>& data,
+                                           size_t* current,
+                                           std::vector<uint8>* data_to_send) {
+  size_t index = *current;
+  uint8 first_byte = Get(data, index);
+  DCHECK_LE(0x80, (first_byte & 0xf0));
+  DCHECK_LE((first_byte & 0xf0), 0xe0);
+
+  const size_t message_size_table[8] = {
+    3, 3, 3, 3, 2, 3, 3, 0,
+  };
+  uint8 code_index = first_byte >> 4;
+  size_t message_size = message_size_table[code_index & 0x7];
+  DCHECK_NE(0u, message_size);
+  DCHECK_LE(message_size, 3u);
+
+  if (GetSize(data) < index + message_size) {
+    // The message is incomplete.
+    return false;
+  }
+
+  data_to_send->push_back((jack_.cable_number << 4) | code_index);
+  for (size_t i = index; i < index + 3; ++i)
+    data_to_send->push_back(i < index + message_size ? Get(data, i) : 0);
+  *current += message_size;
+  return true;
+}
+
+}  // namespace media
diff --git a/media/midi/usb_midi_output_stream.h b/media/midi/usb_midi_output_stream.h
new file mode 100644
index 0000000..008da4c
--- /dev/null
+++ b/media/midi/usb_midi_output_stream.h
@@ -0,0 +1,55 @@
+// Copyright 2014 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_MIDI_USB_MIDI_OUTPUT_STREAM_H_
+#define MEDIA_MIDI_USB_MIDI_OUTPUT_STREAM_H_
+
+#include <vector>
+
+#include "base/basictypes.h"
+#include "media/base/media_export.h"
+#include "media/midi/usb_midi_jack.h"
+
+namespace media {
+
+// UsbMidiOutputStream converts MIDI data to USB-MIDI data.
+// See "USB Device Class Definition for MIDI Devices" Release 1.0,
+// Section 4 "USB-MIDI Event Packets" for details.
+class MEDIA_EXPORT UsbMidiOutputStream {
+ public:
+  explicit UsbMidiOutputStream(const UsbMidiJack& jack);
+
+  // Converts |data| to USB-MIDI data and send it to the jack.
+  void Send(const std::vector<uint8>& data);
+
+ private:
+  size_t GetSize(const std::vector<uint8>& data) const;
+  uint8_t Get(const std::vector<uint8>& data, size_t index) const;
+
+  bool PushSysExMessage(const std::vector<uint8>& data,
+                        size_t* current,
+                        std::vector<uint8>* data_to_send);
+  bool PushSysCommonMessage(const std::vector<uint8>& data,
+                            size_t* current,
+                            std::vector<uint8>* data_to_send);
+  void PushSysRTMessage(const std::vector<uint8>& data,
+                        size_t* current,
+                        std::vector<uint8>* data_to_send);
+  bool PushChannelMessage(const std::vector<uint8>& data,
+                          size_t* current,
+                          std::vector<uint8>* data_to_send);
+
+  static const size_t kPacketContentSize = 3;
+
+  UsbMidiJack jack_;
+  size_t pending_size_;
+  uint8 pending_data_[kPacketContentSize];
+  bool is_sending_sysex_;
+
+  DISALLOW_COPY_AND_ASSIGN(UsbMidiOutputStream);
+};
+
+}  // namespace media
+
+#endif  // MEDIA_MIDI_USB_MIDI_OUTPUT_STREAM_H_
diff --git a/media/midi/usb_midi_output_stream_unittest.cc b/media/midi/usb_midi_output_stream_unittest.cc
new file mode 100644
index 0000000..661d611
--- /dev/null
+++ b/media/midi/usb_midi_output_stream_unittest.cc
@@ -0,0 +1,276 @@
+// Copyright 2014 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/midi/usb_midi_output_stream.h"
+
+#include <string>
+#include <vector>
+
+#include "base/memory/scoped_ptr.h"
+#include "base/strings/stringprintf.h"
+#include "media/midi/usb_midi_device.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace media {
+
+namespace {
+
+template<typename T, size_t N>
+std::vector<T> ToVector(const T((&array)[N])) {
+  return std::vector<T>(array, array + N);
+}
+
+class MockUsbMidiDevice : public UsbMidiDevice {
+ public:
+  MockUsbMidiDevice() {}
+  virtual ~MockUsbMidiDevice() {}
+
+  virtual std::vector<uint8> GetDescriptor() OVERRIDE {
+    return std::vector<uint8>();
+  }
+
+  virtual void Send(int endpoint_number, const std::vector<uint8>& data)
+      OVERRIDE {
+    for (size_t i = 0; i < data.size(); ++i) {
+      log_ += base::StringPrintf("0x%02x ", data[i]);
+    }
+    log_ += base::StringPrintf("(endpoint = %d)\n", endpoint_number);
+  }
+
+  const std::string& log() const { return log_; }
+
+  void ClearLog() { log_ = ""; }
+
+ private:
+  std::string log_;
+
+  DISALLOW_COPY_AND_ASSIGN(MockUsbMidiDevice);
+};
+
+class UsbMidiOutputStreamTest : public ::testing::Test {
+ protected:
+  UsbMidiOutputStreamTest() {
+    UsbMidiJack jack(&device_, 1, 2, 4);
+    stream_.reset(new UsbMidiOutputStream(jack));
+  }
+
+  MockUsbMidiDevice device_;
+  scoped_ptr<UsbMidiOutputStream> stream_;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(UsbMidiOutputStreamTest);
+};
+
+TEST_F(UsbMidiOutputStreamTest, SendEmpty) {
+  stream_->Send(std::vector<uint8>());
+
+  EXPECT_EQ("", device_.log());
+}
+
+TEST_F(UsbMidiOutputStreamTest, SendNoteOn) {
+  uint8 data[] = { 0x90, 0x45, 0x7f};
+
+  stream_->Send(ToVector(data));
+  EXPECT_EQ("0x29 0x90 0x45 0x7f (endpoint = 4)\n", device_.log());
+}
+
+TEST_F(UsbMidiOutputStreamTest, SendNoteOnPending) {
+  stream_->Send(std::vector<uint8>(1, 0x90));
+  stream_->Send(std::vector<uint8>(1, 0x45));
+  EXPECT_EQ("", device_.log());
+
+  stream_->Send(std::vector<uint8>(1, 0x7f));
+  EXPECT_EQ("0x29 0x90 0x45 0x7f (endpoint = 4)\n", device_.log());
+  device_.ClearLog();
+
+  stream_->Send(std::vector<uint8>(1, 0x90));
+  stream_->Send(std::vector<uint8>(1, 0x45));
+  EXPECT_EQ("", device_.log());
+}
+
+TEST_F(UsbMidiOutputStreamTest, SendNoteOnBurst) {
+  uint8 data1[] = { 0x90, };
+  uint8 data2[] = { 0x45, 0x7f, 0x90, 0x45, 0x71, 0x90, 0x45, 0x72, 0x90, };
+
+  stream_->Send(ToVector(data1));
+  stream_->Send(ToVector(data2));
+  EXPECT_EQ("0x29 0x90 0x45 0x7f "
+            "0x29 0x90 0x45 0x71 "
+            "0x29 0x90 0x45 0x72 (endpoint = 4)\n", device_.log());
+}
+
+TEST_F(UsbMidiOutputStreamTest, SendNoteOff) {
+  uint8 data[] = { 0x80, 0x33, 0x44, };
+
+  stream_->Send(ToVector(data));
+  EXPECT_EQ("0x28 0x80 0x33 0x44 (endpoint = 4)\n", device_.log());
+}
+
+TEST_F(UsbMidiOutputStreamTest, SendPolyphonicKeyPress) {
+  uint8 data[] = { 0xa0, 0x33, 0x44, };
+
+  stream_->Send(ToVector(data));
+  EXPECT_EQ("0x2a 0xa0 0x33 0x44 (endpoint = 4)\n", device_.log());
+}
+
+TEST_F(UsbMidiOutputStreamTest, SendControlChange) {
+  uint8 data[] = { 0xb7, 0x33, 0x44, };
+
+  stream_->Send(ToVector(data));
+  EXPECT_EQ("0x2b 0xb7 0x33 0x44 (endpoint = 4)\n", device_.log());
+}
+
+TEST_F(UsbMidiOutputStreamTest, SendProgramChange) {
+  uint8 data[] = { 0xc2, 0x33, };
+
+  stream_->Send(ToVector(data));
+  EXPECT_EQ("0x2c 0xc2 0x33 0x00 (endpoint = 4)\n", device_.log());
+}
+
+TEST_F(UsbMidiOutputStreamTest, SendChannelPressure) {
+  uint8 data[] = { 0xd1, 0x33, 0x44, };
+
+  stream_->Send(ToVector(data));
+  EXPECT_EQ("0x2d 0xd1 0x33 0x44 (endpoint = 4)\n", device_.log());
+}
+
+TEST_F(UsbMidiOutputStreamTest, SendPitchWheelChange) {
+  uint8 data[] = { 0xe4, 0x33, 0x44, };
+
+  stream_->Send(ToVector(data));
+  EXPECT_EQ("0x2e 0xe4 0x33 0x44 (endpoint = 4)\n", device_.log());
+}
+
+TEST_F(UsbMidiOutputStreamTest, SendTwoByteSysEx) {
+  uint8 data[] = { 0xf0, 0xf7, };
+
+  stream_->Send(ToVector(data));
+  EXPECT_EQ("0x26 0xf0 0xf7 0x00 (endpoint = 4)\n", device_.log());
+}
+
+TEST_F(UsbMidiOutputStreamTest, SendThreeByteSysEx) {
+  uint8 data[] = { 0xf0, 0x4f, 0xf7, };
+
+  stream_->Send(ToVector(data));
+  EXPECT_EQ("0x27 0xf0 0x4f 0xf7 (endpoint = 4)\n", device_.log());
+}
+
+TEST_F(UsbMidiOutputStreamTest, SendFourByteSysEx) {
+  uint8 data[] = { 0xf0, 0x00, 0x01, 0xf7, };
+
+  stream_->Send(ToVector(data));
+  EXPECT_EQ("0x24 0xf0 0x00 0x01 "
+            "0x25 0xf7 0x00 0x00 (endpoint = 4)\n", device_.log());
+}
+
+TEST_F(UsbMidiOutputStreamTest, SendFiveByteSysEx) {
+  uint8 data[] = { 0xf0, 0x00, 0x01, 0x02, 0xf7, };
+
+  stream_->Send(ToVector(data));
+  EXPECT_EQ("0x24 0xf0 0x00 0x01 "
+            "0x26 0x02 0xf7 0x00 (endpoint = 4)\n", device_.log());
+}
+
+TEST_F(UsbMidiOutputStreamTest, SendSixByteSysEx) {
+  uint8 data[] = { 0xf0, 0x00, 0x01, 0x02, 0x03, 0xf7, };
+
+  stream_->Send(ToVector(data));
+  EXPECT_EQ("0x24 0xf0 0x00 0x01 "
+            "0x27 0x02 0x03 0xf7 (endpoint = 4)\n", device_.log());
+}
+
+TEST_F(UsbMidiOutputStreamTest, SendPendingSysEx) {
+  uint8 data1[] = { 0xf0, 0x33, };
+  uint8 data2[] = { 0x44, 0x55, 0x66, };
+  uint8 data3[] = { 0x77, 0x88, 0x99, 0xf7, };
+
+  stream_->Send(ToVector(data1));
+  EXPECT_EQ("", device_.log());
+
+  stream_->Send(ToVector(data2));
+  EXPECT_EQ("0x24 0xf0 0x33 0x44 (endpoint = 4)\n", device_.log());
+  device_.ClearLog();
+
+  stream_->Send(ToVector(data3));
+  EXPECT_EQ("0x24 0x55 0x66 0x77 0x27 0x88 0x99 0xf7 (endpoint = 4)\n",
+            device_.log());
+}
+
+TEST_F(UsbMidiOutputStreamTest, SendNoteOnAfterSysEx) {
+  uint8 data[] = { 0xf0, 0x00, 0x01, 0x02, 0x03, 0xf7, 0x90, 0x44, 0x33, };
+
+  stream_->Send(ToVector(data));
+  EXPECT_EQ("0x24 0xf0 0x00 0x01 "
+            "0x27 0x02 0x03 0xf7 "
+            "0x29 0x90 0x44 0x33 (endpoint = 4)\n", device_.log());
+}
+
+TEST_F(UsbMidiOutputStreamTest, SendTimeCodeQuarterFrame) {
+  uint8 data[] = { 0xf1, 0x22, };
+
+  stream_->Send(ToVector(data));
+  EXPECT_EQ("0x22 0xf1 0x22 0x00 (endpoint = 4)\n", device_.log());
+}
+
+TEST_F(UsbMidiOutputStreamTest, SendSongPositionPointer) {
+  uint8 data[] = { 0xf2, 0x22, 0x33, };
+
+  stream_->Send(ToVector(data));
+  EXPECT_EQ("0x23 0xf2 0x22 0x33 (endpoint = 4)\n", device_.log());
+}
+
+TEST_F(UsbMidiOutputStreamTest, SendSongSelect) {
+  uint8 data[] = { 0xf3, 0x22, };
+
+  stream_->Send(ToVector(data));
+  EXPECT_EQ("0x22 0xf3 0x22 0x00 (endpoint = 4)\n", device_.log());
+}
+
+TEST_F(UsbMidiOutputStreamTest, TuneRequest) {
+  uint8 data[] = { 0xf6, };
+
+  stream_->Send(ToVector(data));
+  EXPECT_EQ("0x25 0xf6 0x00 0x00 (endpoint = 4)\n", device_.log());
+}
+
+TEST_F(UsbMidiOutputStreamTest, SendSongPositionPointerPending) {
+  uint8 data1[] = { 0xf2, 0x22, };
+  uint8 data2[] = { 0x33, };
+
+  stream_->Send(ToVector(data1));
+  EXPECT_EQ("", device_.log());
+
+  stream_->Send(ToVector(data2));
+  EXPECT_EQ("0x23 0xf2 0x22 0x33 (endpoint = 4)\n", device_.log());
+}
+
+TEST_F(UsbMidiOutputStreamTest, SendRealTimeMessages) {
+  uint8 data[] = { 0xf8, 0xfa, 0xfb, 0xfc, 0xfe, 0xff, };
+
+  stream_->Send(ToVector(data));
+  EXPECT_EQ("0x25 0xf8 0x00 0x00 "
+            "0x25 0xfa 0x00 0x00 "
+            "0x25 0xfb 0x00 0x00 "
+            "0x25 0xfc 0x00 0x00 "
+            "0x25 0xfe 0x00 0x00 "
+            "0x25 0xff 0x00 0x00 (endpoint = 4)\n", device_.log());
+}
+
+TEST_F(UsbMidiOutputStreamTest, SendRealTimeInSysExMessage) {
+  uint8 data[] = {
+    0xf0, 0x00, 0x01, 0x02,
+    0xf8, 0xfa,
+    0x03, 0xf7,
+  };
+
+  stream_->Send(ToVector(data));
+  EXPECT_EQ("0x24 0xf0 0x00 0x01 "
+            "0x25 0xf8 0x00 0x00 "
+            "0x25 0xfa 0x00 0x00 "
+            "0x27 0x02 0x03 0xf7 (endpoint = 4)\n", device_.log());
+}
+
+}  // namespace
+
+}  // namespace media