diff --git a/CMakeLists.txt b/CMakeLists.txt
index 0e9ce9d..06d7b5a 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -141,6 +141,7 @@ if(WITH_API)
   list(APPEND MYNTEYE_SRCS
     src/api/api.cc
     src/api/synthetic.cc
+    src/api/processor/processor.cc
   )
 endif()
 
diff --git a/src/api/api.cc b/src/api/api.cc
index d6585c1..614f94b 100644
--- a/src/api/api.cc
+++ b/src/api/api.cc
@@ -2,6 +2,8 @@
 
 #include <glog/logging.h>
 
+#include <thread>
+
 #include "mynteye/utils.h"
 
 #include "api/synthetic.h"
@@ -31,7 +33,7 @@ Model API::GetModel() const {
 }
 
 bool API::Supports(const Stream &stream) const {
-  return device_->Supports(stream);
+  return synthetic_->Supports(stream);
 }
 
 bool API::Supports(const Capabilities &capability) const {
@@ -92,6 +94,80 @@ bool API::RunOptionAction(const Option &option) const {
   return device_->RunOptionAction(option);
 }
 
+void API::SetStreamCallback(const Stream &stream, stream_callback_t callback) {
+  synthetic_->SetStreamCallback(stream, callback);
+}
+
+void API::SetMotionCallback(motion_callback_t callback) {
+  static auto callback_ = callback;
+  if (callback_) {
+    device_->SetMotionCallback(
+        [](const device::MotionData &data) { callback_({data.imu}); });
+  } else {
+    device_->SetMotionCallback(nullptr);
+  }
+}
+
+bool API::HasStreamCallback(const Stream &stream) const {
+  return synthetic_->HasStreamCallback(stream);
+}
+
+bool API::HasMotionCallback() const {
+  return device_->HasMotionCallback();
+}
+
+void API::Start(const Source &source) {
+  if (source == Source::VIDEO_STREAMING) {
+    synthetic_->StartVideoStreaming();
+  } else if (source == Source::MOTION_TRACKING) {
+    device_->StartMotionTracking();
+  } else if (source == Source::ALL) {
+    Start(Source::VIDEO_STREAMING);
+    Start(Source::MOTION_TRACKING);
+  } else {
+    LOG(FATAL) << "Unsupported source :(";
+  }
+}
+
+void API::Stop(const Source &source) {
+  if (source == Source::VIDEO_STREAMING) {
+    synthetic_->StopVideoStreaming();
+  } else if (source == Source::MOTION_TRACKING) {
+    device_->StopMotionTracking();
+  } else if (source == Source::ALL) {
+    Stop(Source::MOTION_TRACKING);
+    // Must stop motion tracking before video streaming and sleep a moment here
+    std::this_thread::sleep_for(std::chrono::milliseconds(10));
+    Stop(Source::VIDEO_STREAMING);
+  } else {
+    LOG(FATAL) << "Unsupported source :(";
+  }
+}
+
+void API::WaitForStreams() {
+  synthetic_->WaitForStreams();
+}
+
+api::StreamData API::GetStreamData(const Stream &stream) {
+  return synthetic_->GetStreamData(stream);
+}
+
+std::vector<api::StreamData> API::GetStreamDatas(const Stream &stream) {
+  return synthetic_->GetStreamDatas(stream);
+}
+
+void API::EnableMotionDatas(std::size_t max_size) {
+  device_->EnableMotionDatas(max_size);
+}
+
+std::vector<api::MotionData> API::GetMotionDatas() {
+  std::vector<api::MotionData> datas;
+  for (auto &&data : device_->GetMotionDatas()) {
+    datas.push_back({data.imu});
+  }
+  return datas;
+}
+
 std::shared_ptr<Device> API::device() {
   return device_;
 }
diff --git a/src/api/api.h b/src/api/api.h
index 7a45f9f..d226e70 100644
--- a/src/api/api.h
+++ b/src/api/api.h
@@ -2,6 +2,9 @@
 #define MYNTEYE_API_H_
 #pragma once
 
+#include <opencv2/core/core.hpp>
+
+#include <limits>
 #include <memory>
 #include <string>
 #include <vector>
@@ -14,8 +17,24 @@ MYNTEYE_BEGIN_NAMESPACE
 class Device;
 class Synthetic;
 
+namespace api {
+
+struct MYNTEYE_API StreamData {
+  std::shared_ptr<ImgData> img;
+  cv::Mat frame;
+};
+
+struct MYNTEYE_API MotionData {
+  std::shared_ptr<ImuData> imu;
+};
+
+}  // namespace api
+
 class MYNTEYE_API API {
  public:
+  using stream_callback_t = std::function<void(const api::StreamData &data)>;
+  using motion_callback_t = std::function<void(const api::MotionData &data)>;
+
   explicit API(std::shared_ptr<Device> device);
   /*virtual*/ ~API();
 
@@ -48,6 +67,24 @@ class MYNTEYE_API API {
 
   bool RunOptionAction(const Option &option) const;
 
+  void SetStreamCallback(const Stream &stream, stream_callback_t callback);
+  void SetMotionCallback(motion_callback_t callback);
+
+  bool HasStreamCallback(const Stream &stream) const;
+  bool HasMotionCallback() const;
+
+  void Start(const Source &source);
+  void Stop(const Source &source);
+
+  void WaitForStreams();
+
+  api::StreamData GetStreamData(const Stream &stream);
+  std::vector<api::StreamData> GetStreamDatas(const Stream &stream);
+
+  void EnableMotionDatas(
+      std::size_t max_size = std::numeric_limits<std::size_t>::max());
+  std::vector<api::MotionData> GetMotionDatas();
+
   std::shared_ptr<Device> device();
 
  private:
diff --git a/src/api/processor/object.h b/src/api/processor/object.h
new file mode 100644
index 0000000..51faf7b
--- /dev/null
+++ b/src/api/processor/object.h
@@ -0,0 +1,62 @@
+#ifndef MYNTEYE_OBJECT_H_  // NOLINT
+#define MYNTEYE_OBJECT_H_
+#pragma once
+
+#include <opencv2/core/core.hpp>
+
+#include "mynteye/mynteye.h"
+
+MYNTEYE_BEGIN_NAMESPACE
+
+/**
+ * Input & output object.
+ */
+struct Object {
+  Object() = default;
+  virtual ~Object() = default;
+
+  virtual Object *Clone() const = 0;
+
+  template <typename T>
+  static T *Cast(Object *obj) {
+    return dynamic_cast<T *>(obj);
+  }
+
+  template <typename T>
+  static const T *Cast(const Object *obj) {
+    return dynamic_cast<const T *>(obj);
+  }
+};
+
+struct ObjMat : public Object {
+  ObjMat() = default;
+  explicit ObjMat(const cv::Mat &value) : value(value) {}
+
+  cv::Mat value;
+
+  Object *Clone() const {
+    ObjMat *mat = new ObjMat;
+    mat->value = value.clone();
+    return mat;
+  }
+};
+
+struct ObjMat2 : public Object {
+  ObjMat2() = default;
+  ObjMat2(const cv::Mat &first, const cv::Mat &second)
+      : first(first), second(second) {}
+
+  cv::Mat first;
+  cv::Mat second;
+
+  Object *Clone() const {
+    ObjMat2 *mat2 = new ObjMat2;
+    mat2->first = first.clone();
+    mat2->second = second.clone();
+    return mat2;
+  }
+};
+
+MYNTEYE_END_NAMESPACE
+
+#endif  // MYNTEYE_OBJECT_H_  NOLINT
diff --git a/src/api/processor/processor.cc b/src/api/processor/processor.cc
new file mode 100644
index 0000000..b3f6491
--- /dev/null
+++ b/src/api/processor/processor.cc
@@ -0,0 +1,180 @@
+#include "api/processor/processor.h"
+
+#include <glog/logging.h>
+
+#include <utility>
+
+MYNTEYE_BEGIN_NAMESPACE
+
+Processor::Processor()
+    : activated_(false),
+      input_ready_(false),
+      idle_(true),
+      dropped_count_(0),
+      input_(nullptr),
+      output_(nullptr),
+      output_result_(nullptr),
+      pre_callback_(nullptr),
+      post_callback_(nullptr),
+      callback_(nullptr),
+      parent_(nullptr) {
+  VLOG(2) << __func__;
+}
+
+Processor::~Processor() {
+  VLOG(2) << __func__;
+  Deactivate();
+  input_.reset(nullptr);
+  output_.reset(nullptr);
+  output_result_.reset(nullptr);
+  childs_.clear();
+}
+
+std::string Processor::Name() {
+  return "Processor";
+}
+
+void Processor::AddChild(const std::shared_ptr<Processor> &child) {
+  child->parent_ = this;
+  childs_.push_back(child);
+}
+
+void Processor::RemoveChild(const std::shared_ptr<Processor> &child) {
+  childs_.remove(child);
+}
+
+std::list<std::shared_ptr<Processor>> Processor::GetChilds() {
+  return childs_;
+}
+
+void Processor::SetPreProcessCallback(PreProcessCallback callback) {
+  pre_callback_ = std::move(callback);
+}
+
+void Processor::SetPostProcessCallback(PostProcessCallback callback) {
+  post_callback_ = std::move(callback);
+}
+
+void Processor::SetProcessCallback(ProcessCallback callback) {
+  callback_ = std::move(callback);
+}
+
+void Processor::Activate() {
+  if (activated_)
+    return;
+  activated_ = true;
+  {
+    // Activate all parents
+    Processor *parent = parent_;
+    while (parent != nullptr) {
+      parent->Activate();
+      parent = parent->parent_;
+    }
+  }
+  thread_ = std::thread(&Processor::Run, this);
+  // thread_.detach();
+}
+
+void Processor::Deactivate() {
+  if (!activated_)
+    return;
+  activated_ = false;
+  {
+    std::lock_guard<std::mutex> lk(mtx_input_ready_);
+    input_ready_ = true;
+  }
+  cond_input_ready_.notify_all();
+  thread_.join();
+}
+
+bool Processor::IsActivated() {
+  return activated_;
+}
+
+bool Processor::IsIdle() {
+  std::lock_guard<std::mutex> lk(mtx_state_);
+  return idle_;
+}
+
+bool Processor::Process(const Object *const in) {
+  if (!activated_)
+    return false;
+  if (!idle_) {
+    std::lock_guard<std::mutex> lk(mtx_state_);
+    if (!idle_) {
+      ++dropped_count_;
+      return false;
+    }
+  }
+  {
+    std::lock_guard<std::mutex> lk(mtx_input_ready_);
+    input_.reset(in->Clone());
+    input_ready_ = true;
+  }
+  cond_input_ready_.notify_all();
+  return true;
+}
+
+Object *Processor::GetOutput() {
+  std::lock_guard<std::mutex> lk(mtx_result_);
+  return output_result_.get();
+}
+
+std::uint64_t Processor::GetDroppedCount() {
+  std::lock_guard<std::mutex> lk(mtx_state_);
+  return dropped_count_;
+}
+
+void Processor::Run() {
+  VLOG(2) << Name() << " thread start";
+  while (true) {
+    std::unique_lock<std::mutex> lk(mtx_input_ready_);
+    cond_input_ready_.wait(lk, [this] { return input_ready_; });
+
+    if (!activated_) {
+      SetIdle(true);
+      input_ready_ = false;
+      break;
+    }
+    SetIdle(false);
+
+    if (!output_) {
+      output_.reset(OnCreateOutput());
+    }
+
+    if (pre_callback_) {
+      pre_callback_(input_.get());
+    }
+    if (callback_) {
+      if (!callback_(input_.get(), output_.get(), parent_)) {
+        OnProcess(input_.get(), output_.get(), parent_);
+      }
+    } else {
+      OnProcess(input_.get(), output_.get(), parent_);
+    }
+    if (post_callback_) {
+      post_callback_(output_.get());
+    }
+    {
+      std::unique_lock<std::mutex> lk(mtx_result_);
+      output_result_.reset(output_->Clone());
+    }
+
+    if (!childs_.empty()) {
+      for (auto child : childs_) {
+        child->Process(output_.get());
+      }
+    }
+
+    SetIdle(true);
+    input_ready_ = false;
+  }
+  VLOG(2) << Name() << " thread end";
+}
+
+void Processor::SetIdle(bool idle) {
+  std::lock_guard<std::mutex> lk(mtx_state_);
+  idle_ = idle;
+}
+
+MYNTEYE_END_NAMESPACE
diff --git a/src/api/processor/processor.h b/src/api/processor/processor.h
new file mode 100644
index 0000000..d4a0906
--- /dev/null
+++ b/src/api/processor/processor.h
@@ -0,0 +1,98 @@
+#ifndef MYNTEYE_PROCESSOR_H_  // NOLINT
+#define MYNTEYE_PROCESSOR_H_
+#pragma once
+
+#include <condition_variable>
+#include <cstdint>
+#include <functional>
+#include <list>
+#include <memory>
+#include <mutex>
+#include <string>
+#include <thread>
+
+#include "mynteye/mynteye.h"
+
+#include "api/processor/object.h"
+
+MYNTEYE_BEGIN_NAMESPACE
+
+class Processor /*: public std::enable_shared_from_this<Processor>*/ {
+ public:
+  using PreProcessCallback = std::function<void(Object *const)>;
+  using PostProcessCallback = std::function<void(Object *const)>;
+  using ProcessCallback = std::function<bool(
+      Object *const in, Object *const out, Processor *const parent)>;
+
+  Processor();
+  virtual ~Processor();
+
+  virtual std::string Name();
+
+  void AddChild(const std::shared_ptr<Processor> &child);
+
+  void RemoveChild(const std::shared_ptr<Processor> &child);
+
+  std::list<std::shared_ptr<Processor>> GetChilds();
+
+  void SetPreProcessCallback(PreProcessCallback callback);
+  void SetPostProcessCallback(PostProcessCallback callback);
+  void SetProcessCallback(ProcessCallback callback);
+
+  void Activate();
+  void Deactivate();
+  bool IsActivated();
+
+  bool IsIdle();
+
+  /** Returns dropped or not. */
+  bool Process(const Object *const in);
+
+  /**
+   * Returns the last output.
+   * @note Returns null if not output now.
+   */
+  Object *GetOutput();
+
+  std::uint64_t GetDroppedCount();
+
+ protected:
+  virtual Object *OnCreateOutput() = 0;
+  virtual void OnProcess(
+      Object *const in, Object *const out, Processor *const parent) = 0;
+
+ private:
+  /** Run in standalone thread. */
+  void Run();
+
+  void SetIdle(bool idle);
+
+  bool activated_;
+
+  bool input_ready_;
+  std::mutex mtx_input_ready_;
+  std::condition_variable cond_input_ready_;
+
+  bool idle_;
+  std::uint64_t dropped_count_;
+  std::mutex mtx_state_;
+
+  std::unique_ptr<Object> input_;
+  std::unique_ptr<Object> output_;
+
+  std::unique_ptr<Object> output_result_;
+  std::mutex mtx_result_;
+
+  PreProcessCallback pre_callback_;
+  PostProcessCallback post_callback_;
+  ProcessCallback callback_;
+
+  Processor *parent_;
+  std::list<std::shared_ptr<Processor>> childs_;
+
+  std::thread thread_;
+};
+
+MYNTEYE_END_NAMESPACE
+
+#endif  // MYNTEYE_PROCESSOR_H_  NOLINT
diff --git a/src/api/synthetic.cc b/src/api/synthetic.cc
index 446d06e..90f12e0 100644
--- a/src/api/synthetic.cc
+++ b/src/api/synthetic.cc
@@ -2,7 +2,8 @@
 
 #include <glog/logging.h>
 
-#include "api/api.h"
+#include "api/processor/processor.h"
+#include "device/device.h"
 
 MYNTEYE_BEGIN_NAMESPACE
 
@@ -14,4 +15,35 @@ Synthetic::~Synthetic() {
   VLOG(2) << __func__;
 }
 
+bool Synthetic::Supports(const Stream &stream) const {
+  return api_->device()->Supports(stream);
+}
+
+void Synthetic::SetStreamCallback(
+    const Stream &stream, stream_callback_t callback) {
+  UNUSED(stream)
+  UNUSED(callback)
+}
+
+bool Synthetic::HasStreamCallback(const Stream &stream) const {
+  UNUSED(stream)
+  return false;
+}
+
+void Synthetic::StartVideoStreaming() {}
+
+void Synthetic::StopVideoStreaming() {}
+
+void Synthetic::WaitForStreams() {}
+
+api::StreamData Synthetic::GetStreamData(const Stream &stream) {
+  UNUSED(stream)
+  return {};
+}
+
+std::vector<api::StreamData> Synthetic::GetStreamDatas(const Stream &stream) {
+  UNUSED(stream)
+  return {};
+}
+
 MYNTEYE_END_NAMESPACE
diff --git a/src/api/synthetic.h b/src/api/synthetic.h
index 6c3a1ae..645a934 100644
--- a/src/api/synthetic.h
+++ b/src/api/synthetic.h
@@ -2,19 +2,40 @@
 #define MYNTEYE_SYNTHETIC_H_
 #pragma once
 
-#include "mynteye/mynteye.h"
+#include <memory>
+#include <vector>
+
+#include "api/api.h"
 
 MYNTEYE_BEGIN_NAMESPACE
 
 class API;
+class Processor;
 
 class Synthetic {
  public:
+  using stream_callback_t = API::stream_callback_t;
+
   explicit Synthetic(API *api);
   ~Synthetic();
 
+  bool Supports(const Stream &stream) const;
+
+  void SetStreamCallback(const Stream &stream, stream_callback_t callback);
+  bool HasStreamCallback(const Stream &stream) const;
+
+  void StartVideoStreaming();
+  void StopVideoStreaming();
+
+  void WaitForStreams();
+
+  api::StreamData GetStreamData(const Stream &stream);
+  std::vector<api::StreamData> GetStreamDatas(const Stream &stream);
+
  private:
   API *api_;
+
+  std::vector<std::shared_ptr<Processor>> processors_;
 };
 
 MYNTEYE_END_NAMESPACE
diff --git a/src/device/device.h b/src/device/device.h
index a504d6c..d22b1e5 100644
--- a/src/device/device.h
+++ b/src/device/device.h
@@ -29,6 +29,7 @@ class DeviceWriter;
 
 struct DeviceInfo;
 
+class API;
 class Channels;
 class Motions;
 class Streams;
@@ -104,10 +105,6 @@ class MYNTEYE_API Device {
     return device_;
   }
 
-  std::shared_ptr<DeviceInfo> device_info() const {
-    return device_info_;
-  }
-
   const StreamRequest &GetStreamRequest(const Capabilities &capability);
 
   virtual void StartVideoStreaming();
@@ -151,6 +148,7 @@ class MYNTEYE_API Device {
     return channels_;
   }
 
+  friend API;
   friend tools::DeviceWriter;
 };