refactor video capture in browser process to support device sharing across multiple renderer proc...

content/browser/renderer_host/media/video_capture_controller.cc

 // 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 "content/browser/renderer_host/media/video_capture_controller.h"
 
 #include "base/bind.h"
 #include "base/stl_util.h"
 #include "content/browser/browser_thread.h"
 #include "content/browser/renderer_host/media/media_stream_manager.h"
 #include "content/browser/renderer_host/media/video_capture_manager.h"
 #include "media/base/yuv_convert.h"
 
-// The number of TransportDIBs VideoCaptureController allocate.
+// The number of DIBs VideoCaptureController allocate.
 static const size_t kNoOfDIBS = 3;
 
+struct VideoCaptureController::ControllerClient {
+  ControllerClient(
+      const VideoCaptureControllerID& id,
+      VideoCaptureControllerEventHandler* handler,
+      base::ProcessHandle render_process,
+      const media::VideoCaptureParams& params)
+      : controller_id(id),
+        event_handler(handler),
+        render_process_handle(render_process),
+        parameters(params),
+        report_ready_to_delete(false) {
+  }
+
+  ~ControllerClient() {}
+
+  // ID used for identifying this object.
+  VideoCaptureControllerID controller_id;
+  VideoCaptureControllerEventHandler* event_handler;
+  // Handle to the render process that will receive the DIBs.

[scherkus (not reviewing), 2011/10/31 03:20:18]

nit: add blank lines before // comments

[wjia(left Chromium), 2011/10/31 22:02:44]

Done.

+  base::ProcessHandle render_process_handle;
+  media::VideoCaptureParams parameters;
+  // Buffers used by this client.
+  std::list<int> buffers;
+  bool report_ready_to_delete;

[scherkus (not reviewing), 2011/10/31 03:20:18]

this is a pretty important field -- I'd encourage some documentation here

[wjia(left Chromium), 2011/10/31 22:02:44]

Done.

+};
+
 VideoCaptureController::VideoCaptureController(
-    const VideoCaptureControllerID& id,
-    base::ProcessHandle render_process,
-    VideoCaptureControllerEventHandler* event_handler,
     media_stream::VideoCaptureManager* video_capture_manager)
-    : render_handle_(render_process),
-      report_ready_to_delete_(false),
-      event_handler_(event_handler),
-      id_(id),
-      video_capture_manager_(video_capture_manager) {
-  memset(&params_, 0, sizeof(params_));
+    : frame_info_available_(false),
+      video_capture_manager_(video_capture_manager),
+      device_in_use_(false),
+      state_(media::VideoCapture::kStopped) {
+  memset(&current_params_, 0, sizeof(current_params_));
 }
 
 VideoCaptureController::~VideoCaptureController() {
-  // Delete all TransportDIBs.
+  // Delete all DIBs.
   STLDeleteContainerPairSecondPointers(owned_dibs_.begin(),
                                        owned_dibs_.end());
+  STLDeleteContainerPointers(controller_clients_.begin(),
+                             controller_clients_.end());
+  STLDeleteContainerPointers(pending_clients_.begin(),
+                             pending_clients_.end());
 }
 
 void VideoCaptureController::StartCapture(
+    const VideoCaptureControllerID& id,
+    VideoCaptureControllerEventHandler* event_handler,
+    base::ProcessHandle render_process,
     const media::VideoCaptureParams& params) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
-
-  params_ = params;
+  // Signal error in case device is already in error state.
+  if (state_ == media::VideoCapture::kError) {
+    event_handler->OnError(id);
+    return;
+  }
+
+  // Do nothing if this client has called StartCapture before.
+  if (FindClient(id, event_handler, controller_clients_) !=
+      controller_clients_.end() ||
+      FindClient(id, event_handler, pending_clients_) !=
+      pending_clients_.end())
+    return;
+
+  ControllerClient* client = new ControllerClient(id, event_handler,
+                                                  render_process, params);
+  // In case capture has been started, need to check different condtions.
+  if (state_ == media::VideoCapture::kStarted) {
+    // This client has higher resolution than what is currently requested.
+    // Need restart capturing.
+    if (params.width > current_params_.width ||
+        params.height > current_params_.height) {
+      video_capture_manager_->Stop(current_params_.session_id,
+          base::Bind(&VideoCaptureController::OnDeviceStopped, this));
+      frame_info_available_ = false;
+      state_ = media::VideoCapture::kStopping;
+      pending_clients_.push_back(client);
+      return;
+    }
+
+    // This client's resolution is no larger than what's currently requested.
+    // When frame_info has been returned by device, send them to client.
+    if (frame_info_available_) {
+      SendFrameInfoAndBuffers(client);
+    }
+    controller_clients_.push_back(client);
+    return;
+  }
+
+  // In case the device is in the middle of stopping, put the client in
+  // pending queue.
+  if (state_ == media::VideoCapture::kStopping) {
+    pending_clients_.push_back(client);
+    return;
+  }
+
+  // Fresh start.
+  controller_clients_.push_back(client);
+  current_params_ = params;
   // Order the manager to start the actual capture.
   video_capture_manager_->Start(params, this);
-}
-
-void VideoCaptureController::StopCapture(base::Closure stopped_cb) {
+  state_ = media::VideoCapture::kStarted;
+}
+
+void VideoCaptureController::StopCapture(
+    const VideoCaptureControllerID& id,
+    VideoCaptureControllerEventHandler* event_handler,
+    bool force_buffer_return) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
 
-  video_capture_manager_->Stop(params_.session_id,
-      base::Bind(&VideoCaptureController::OnDeviceStopped, this, stopped_cb));
-}
-
-void VideoCaptureController::ReturnBuffer(int buffer_id) {
+  ControllerClients::iterator cit;
+  cit = FindClient(id, event_handler, pending_clients_);

[scherkus (not reviewing), 2011/10/31 03:20:18]

I'd strongly encourage you to have FindClient() return the client pointer itself
(or NULL if not found)

this is an extremely hard to read function and "cit" and "dit" don't make for
very good names when you could have something like "client"

you may have to do another look-up in order to erase the client (perhaps
introduce a DeleteClient()?) from the map, but again we're talking about a very
small list of clients so I'd pick code clarity over avoiding a second look-up

[wjia(left Chromium), 2011/10/31 22:02:44]

Done. std::list has remove(). So no need to have another function to remove
element.

cit and dit have been renamed to client_it and dib_it, respectively.

+  // If the client is still in pending queue, just remove it.
+  if (cit != pending_clients_.end()) {
+    (*cit)->event_handler->OnReadyToDelete((*cit)->controller_id);
+    pending_clients_.erase(cit);
+    return;
+  }
+
+  cit = FindClient(id, event_handler, controller_clients_);
+  // The client should have called StartCapture.
+  DCHECK(cit != controller_clients_.end());
+
+  if (force_buffer_return) {
+    // The client requests to return buffers which means it can't return
+    // buffers normally. After buffers are returned, client is free to
+    // delete itself. No need to call OnReadyToDelete.
+
+    // Return all buffers held by the clients.
+    for (std::list<int>::iterator bit = (*cit)->buffers.begin();
+         bit != (*cit)->buffers.end(); ++bit) {
+      int buffer_id = *bit;
+      ClientSideDIBCount::iterator dit = client_side_dib_count_.find(buffer_id);
+      if (dit == client_side_dib_count_.end())
+        continue;
+
+      if (--dit->second > 0)
+        continue;
+
+      // Now this |buffer_id| is not used by any client.
+      client_side_dib_count_.erase(buffer_id);
+      {
+        base::AutoLock lock(lock_);
+        free_dibs_.push_back(buffer_id);
+      }
+    }
+    (*cit)->buffers.clear();
+  } else {
+    // Normal way to stop capture.
+    if ((*cit)->buffers.size() > 0) {
+      // There are still some buffers held by the client.
+      (*cit)->report_ready_to_delete = true;
+      return;
+    }
+    // No buffer is held by the client. Ready to delete.
+    (*cit)->event_handler->OnReadyToDelete((*cit)->controller_id);
+  }
+
+  delete (*cit);
+  controller_clients_.erase(cit);
+
+  // No more clients. Stop device.
+  if (controller_clients_.size() == 0) {

[scherkus (not reviewing), 2011/10/31 03:20:18]

.empty()

[wjia(left Chromium), 2011/10/31 22:02:44]

Done.

+    video_capture_manager_->Stop(current_params_.session_id,
+        base::Bind(&VideoCaptureController::OnDeviceStopped, this));
+    frame_info_available_ = false;
+    state_ = media::VideoCapture::kStopping;
+  }
+}
+
+void VideoCaptureController::ReturnBuffer(
+    const VideoCaptureControllerID& id,
+    VideoCaptureControllerEventHandler* event_handler,
+    int buffer_id) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
 
-  bool ready_to_delete;
+  ControllerClients::iterator cit = FindClient(id, event_handler,
+                                               controller_clients_);
+  ClientSideDIBCount::iterator dit = client_side_dib_count_.find(buffer_id);
+  // If this buffer is not held by this client, or this client doesn't exist
+  // in controller, do nothing.
+  if (cit == controller_clients_.end() || dit == client_side_dib_count_.end())
+    return;
+
+  (*cit)->buffers.remove(buffer_id);
+  // If this client has called StopCapture and doesn't hold any buffer after
+  // after this return, ready to delete this client.
+  if ((*cit)->report_ready_to_delete && (*cit)->buffers.size() == 0) {

[scherkus (not reviewing), 2011/10/31 03:20:18]

.empty()

[wjia(left Chromium), 2011/10/31 22:02:44]

Done.

+    (*cit)->event_handler->OnReadyToDelete((*cit)->controller_id);
+    delete (*cit);
+    controller_clients_.erase(cit);
+  }
+  if (--dit->second > 0)
+    return;
+
+  // Now this |buffer_id| is not used by any client.
+  client_side_dib_count_.erase(buffer_id);
   {
     base::AutoLock lock(lock_);
     free_dibs_.push_back(buffer_id);
-    ready_to_delete = (free_dibs_.size() == owned_dibs_.size()) &&
-        report_ready_to_delete_;
-  }
-  if (ready_to_delete) {
-    event_handler_->OnReadyToDelete(id_);
-  }
-}
-
+  }
+
+  // When all buffers have been returned by clients and device has been
+  // called to stop, check if restart is needed. This could happen when
+  // some clients call StopCapture before returning all buffers.

[scherkus (not reviewing), 2011/10/31 03:20:18]

is it valid to call StopCapture() before returning all buffers?

can you require all buffers to be returned before calling StopCapture()? it
might help simplify the implementation

[wjia(left Chromium), 2011/10/31 22:02:44]

It's possible that renderer process side sends StopCapture message before all
buffers are returned because some buffers are sent to renderer process before
Host receives StopCapture message, but after renderer process sends StopCapture.

Currently, host doesn't track buffers. It just relay the message to controller.
So it's valid controller gets StopCapture() before that client (i.e., host)
returns all buffers.

We can require host to call StopCapture only after returning all buffers by
moving some logic into VCHost. My take is that the total complexity will be
pretty much same.

+  if (!ClientHasDIB() && state_ == media::VideoCapture::kStopping) {
+    PostStopping();
+  }
+}
+
 ///////////////////////////////////////////////////////////////////////////////
 // Implements VideoCaptureDevice::EventHandler.
 // OnIncomingCapturedFrame is called the thread running the capture device.
 // I.e.- DirectShow thread on windows and v4l2_thread on Linux.
 void VideoCaptureController::OnIncomingCapturedFrame(const uint8* data,
                                                      int length,
                                                      base::Time timestamp) {
   int buffer_id = 0;
   base::SharedMemory* dib = NULL;
-  // Check if there is a TransportDIB to fill.
+  // Check if there is a DIB to fill.
   bool buffer_exist = false;
   {
     base::AutoLock lock(lock_);
-    if (!report_ready_to_delete_ && free_dibs_.size() > 0) {
+    if (free_dibs_.size() > 0) {
       buffer_id = free_dibs_.front();
       free_dibs_.pop_front();
       DIBMap::iterator it = owned_dibs_.find(buffer_id);
       if (it != owned_dibs_.end()) {
         dib = it->second;
         buffer_exist = true;
       }
     }
   }
 
   if (!buffer_exist) {

[scherkus (not reviewing), 2011/10/31 03:20:18]

nit: you could do without buffer_exist by checking dib instead

if (!dib) {
  return;
}

[wjia(left Chromium), 2011/10/31 22:02:44]

Done.

     return;
   }
 
   uint8* target = static_cast<uint8*>(dib->memory());
   CHECK(dib->created_size() >= static_cast<size_t> (frame_info_.width *
                                                     frame_info_.height * 3) /
                                                     2);
 
   // Do color conversion from the camera format to I420.
   switch (frame_info_.color) {
@@ skipping 11 matching lines @@
                               frame_info_.height);
       break;
     }
     case media::VideoCaptureDevice::kRGB24: {
 #if defined(OS_WIN)  // RGB on Windows start at the bottom line.
       uint8* yplane = target;
       uint8* uplane = target + frame_info_.width * frame_info_.height;
       uint8* vplane = uplane + (frame_info_.width * frame_info_.height) / 4;
       int ystride = frame_info_.width;
       int uvstride = frame_info_.width / 2;
       int rgb_stride = - 3 * frame_info_.width;

[scherkus (not reviewing), 2011/10/31 03:20:18]

nit: - 3 -> -3

also the side of this #if could be reduced as the uint8* lines of code are
duplicated

[wjia(left Chromium), 2011/10/31 22:02:44]

Done and more cleanup.

       const uint8* rgb_src = data + 3 * frame_info_.width *
           (frame_info_.height -1);
 #else
       uint8* yplane = target;
       uint8* uplane = target + frame_info_.width * frame_info_.height;
       uint8* vplane = uplane + (frame_info_.width * frame_info_.height) / 4;
       int ystride = frame_info_.width;
       int uvstride = frame_info_.width / 2;
       int rgb_stride = 3 * frame_info_.width;
       const uint8* rgb_src = data;
 #endif
       media::ConvertRGB24ToYUV(rgb_src, yplane, uplane, vplane,
                                frame_info_.width, frame_info_.height,
                                rgb_stride, ystride, uvstride);
       break;
     }
     case media::VideoCaptureDevice::kARGB: {
       uint8* yplane = target;
       uint8* uplane = target +  frame_info_.width * frame_info_.height;

[scherkus (not reviewing), 2011/10/31 03:20:18]

nit: remove extra spaces here

[wjia(left Chromium), 2011/10/31 22:02:44]

Done.

       uint8* vplane = uplane +  (frame_info_.width * frame_info_.height) / 4;
       media::ConvertRGB32ToYUV(data, yplane, uplane, vplane, frame_info_.width,
                                frame_info_.height, frame_info_.width * 4,
                                frame_info_.width, frame_info_.width / 2);
       break;
     }
     default:
       NOTREACHED();
   }
 
-  event_handler_->OnBufferReady(id_, buffer_id, timestamp);
+  BrowserThread::PostTask(BrowserThread::IO,
+      FROM_HERE,
+      base::Bind(&VideoCaptureController::DoIncomingCapturedFrameOnIOThread,
+                 this, buffer_id, timestamp));
 }
 
 void VideoCaptureController::OnError() {
-  event_handler_->OnError(id_);
-  video_capture_manager_->Error(params_.session_id);
+  video_capture_manager_->Error(current_params_.session_id);
+  BrowserThread::PostTask(BrowserThread::IO,
+      FROM_HERE,
+      base::Bind(&VideoCaptureController::DoErrorOnIOThread, this));
 }
 
 void VideoCaptureController::OnFrameInfo(
     const media::VideoCaptureDevice::Capability& info) {
+  BrowserThread::PostTask(BrowserThread::IO,
+      FROM_HERE,
+      base::Bind(&VideoCaptureController::DoFrameInfoOnIOThread,
+                 this, info));
+}
+
+void VideoCaptureController::DoIncomingCapturedFrameOnIOThread(
+    int buffer_id, base::Time timestamp) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
+
+  if (state_ != media::VideoCapture::kStarted) {
+    base::AutoLock lock(lock_);
+    free_dibs_.push_back(buffer_id);
+    return;
+  }
+
+  int count = 0;
+  for (ControllerClients::iterator cit = controller_clients_.begin();
+       cit != controller_clients_.end(); cit++) {
+    if ((*cit)->report_ready_to_delete)
+      continue;
+
+    (*cit)->event_handler->OnBufferReady((*cit)->controller_id,
+                                         buffer_id, timestamp);
+    (*cit)->buffers.push_back(buffer_id);
+    count++;
+  }
+  if (count > 0) {
+    client_side_dib_count_[buffer_id] = count;
+  } else {
+    base::AutoLock lock(lock_);
+    free_dibs_.push_back(buffer_id);
+  }
+}
+
+void VideoCaptureController::DoErrorOnIOThread() {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
+  state_ = media::VideoCapture::kError;
+  ControllerClients::iterator cit;
+  for (cit = controller_clients_.begin();
+       cit != controller_clients_.end(); cit++) {
+    (*cit)->event_handler->OnError((*cit)->controller_id);
+  }
+  for (cit = pending_clients_.begin();
+       cit != pending_clients_.end(); cit++) {
+    (*cit)->event_handler->OnError((*cit)->controller_id);
+  }
+}
+
+void VideoCaptureController::DoFrameInfoOnIOThread(
+    const media::VideoCaptureDevice::Capability info) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
   DCHECK(owned_dibs_.empty());
+
   bool frames_created = true;
   const size_t needed_size = (info.width * info.height * 3) / 2;
+  base::AutoLock lock(lock_);
   for (size_t i = 1; i <= kNoOfDIBS; ++i) {
     base::SharedMemory* shared_memory = new base::SharedMemory();
     if (!shared_memory->CreateAndMapAnonymous(needed_size)) {
       frames_created = false;
       break;
     }
-    base::SharedMemoryHandle remote_handle;
-    shared_memory->ShareToProcess(render_handle_, &remote_handle);
-
-    base::AutoLock lock(lock_);
     owned_dibs_.insert(std::make_pair(i, shared_memory));
     free_dibs_.push_back(i);
-    event_handler_->OnBufferCreated(id_, remote_handle,
-                                    static_cast<int>(needed_size),
-                                    static_cast<int>(i));
+  }
+  // Check whether all DIBs were created successfully.
+  if (!frames_created) {
+    state_ = media::VideoCapture::kError;
+    for (ControllerClients::iterator cit = controller_clients_.begin();
+         cit != controller_clients_.end(); cit++) {
+      (*cit)->event_handler->OnError((*cit)->controller_id);
+    }
+    return;
   }
   frame_info_= info;
-
-  // Check that all DIBs where created successfully.
-  if (!frames_created) {
-    event_handler_->OnError(id_);
-  }
-  event_handler_->OnFrameInfo(id_, info.width, info.height, info.frame_rate);
+  frame_info_available_ = true;
+
+  for (ControllerClients::iterator cit = controller_clients_.begin();
+       cit != controller_clients_.end(); cit++) {
+    SendFrameInfoAndBuffersWithLock((*cit), static_cast<int>(needed_size));
+  }
+}
+
+void VideoCaptureController::SendFrameInfoAndBuffers(ControllerClient* client) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
+  DCHECK(frame_info_available_);
+  const size_t needed_size = (frame_info_.width * frame_info_.height * 3) / 2;
+  base::AutoLock lock(lock_);
+  SendFrameInfoAndBuffersWithLock(client, static_cast<int>(needed_size));
+}
+
+void VideoCaptureController::SendFrameInfoAndBuffersWithLock(
+    ControllerClient* client, int needed_size) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
+  DCHECK(frame_info_available_);
+  client->event_handler->OnFrameInfo(client->controller_id,
+                                     frame_info_.width, frame_info_.height,
+                                     frame_info_.frame_rate);
+  for (DIBMap::iterator dit = owned_dibs_.begin();

[scherkus (not reviewing), 2011/10/31 03:20:18]

do you need lock_ here for accessing owned_dibs_?

if this function is expected to be called while holding the lock (as I think
it's supposed to be), I'd recommend making it stand out a little bit more

instead of "WithLock" try "_Locked"

you may also want to put a lock_.AssertAcquired() at the top of the function

[wjia(left Chromium), 2011/10/31 22:02:44]

lock_ is not needed here. changed correspondingly.

+       dit != owned_dibs_.end(); dit++) {
+    base::SharedMemory* shared_memory = dit->second;
+    int index = dit->first;
+    base::SharedMemoryHandle remote_handle;
+    shared_memory->ShareToProcess(client->render_process_handle,
+                                  &remote_handle);
+    client->event_handler->OnBufferCreated(client->controller_id,
+                                           remote_handle,
+                                           needed_size,
+                                           index);
+  }
+}
+
+// This function is called when all buffers have been returned to controller,
+// or when device is stopped. It decides whether the device needs to be
+// restarted.
+void VideoCaptureController::PostStopping() {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
+  DCHECK_EQ(state_, media::VideoCapture::kStopping);
+
+  // When clients still have some buffers, or device has not been stopped yet,
+  // do nothing.
+  if (ClientHasDIB() || device_in_use_)
+    return;
+
+  // It's safe to free all DIB's on IO thread since device won't send
+  // buffer over.
+  free_dibs_.clear();

[scherkus (not reviewing), 2011/10/31 03:20:18]

do you need lock_ here?

[wjia(left Chromium), 2011/10/31 22:02:44]

lock_ is not needed here. At this point, the device has been fully stopped and
it will not send any buffer to controller, which means free_dibs_ will not
access on device thread. Furthermore, all buffers have been returned to
controller.

+  STLDeleteValues(&owned_dibs_);
+
+  // No more client. Therefore the controller is stopped.
+  if (controller_clients_.size() + pending_clients_.size() == 0) {

[scherkus (not reviewing), 2011/10/31 03:20:18]

.empty()

[wjia(left Chromium), 2011/10/31 22:02:44]

Done.

+    state_ = media::VideoCapture::kStopped;
+    return;
+  }
+
+  // Restart the device.
+  current_params_.width = 0;
+  current_params_.height = 0;
+  ControllerClients::iterator cit;
+  for (cit = controller_clients_.begin();
+       cit != controller_clients_.end(); cit++) {
+    if (current_params_.width < (*cit)->parameters.width)
+      current_params_.width = (*cit)->parameters.width;
+    if (current_params_.height < (*cit)->parameters.height)
+      current_params_.height = (*cit)->parameters.height;
+  }
+  for (cit = pending_clients_.begin();
+       cit != pending_clients_.end(); ) {
+    if (current_params_.width < (*cit)->parameters.width)
+      current_params_.width = (*cit)->parameters.width;
+    if (current_params_.height < (*cit)->parameters.height)
+      current_params_.height = (*cit)->parameters.height;
+    controller_clients_.push_back((*cit));
+    pending_clients_.erase(cit++);
+  }
+  // Request the manager to start the actual capture.
+  video_capture_manager_->Start(current_params_, this);
+  state_ = media::VideoCapture::kStarted;
+}
+
+bool VideoCaptureController::ClientHasDIB() {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
+  for (ClientSideDIBCount::iterator dit = client_side_dib_count_.begin();
+       dit != client_side_dib_count_.end(); dit++) {
+    if (dit->second > 0)
+      return true;
+  }
+  return false;
+}
+
+VideoCaptureController::ControllerClients::iterator
+VideoCaptureController::FindClient(
+    const VideoCaptureControllerID& id,
+    VideoCaptureControllerEventHandler* handler,
+    ControllerClients& clients) {
+  for (ControllerClients::iterator cit = clients.begin();
+       cit != clients.end(); cit++) {
+    if ((*cit)->controller_id == id && (*cit)->event_handler == handler) {
+      return cit;
+    }
+  }
+  return clients.end();
 }
 
 ///////////////////////////////////////////////////////////////////////////////
 // Called by VideoCaptureManager when a device have been stopped.
-// This will report to the event handler that this object is ready to be deleted
-// if all DIBS have been returned.
-void VideoCaptureController::OnDeviceStopped(base::Closure stopped_cb) {
-  bool ready_to_delete_now;
-
-  {
-    base::AutoLock lock(lock_);
-    // Set flag to indicate we need to report when all DIBs have been returned.
-    report_ready_to_delete_ = true;
-    ready_to_delete_now = (free_dibs_.size() == owned_dibs_.size());
-  }
-
-  if (ready_to_delete_now) {
-    event_handler_->OnReadyToDelete(id_);
-  }
-
-  if (!stopped_cb.is_null())
-    stopped_cb.Run();
-}
+void VideoCaptureController::OnDeviceStopped() {
+  BrowserThread::PostTask(BrowserThread::IO,
+      FROM_HERE,
+      base::Bind(&VideoCaptureController::DoDeviceStoppedOnIOThread, this));
+}
+
+void VideoCaptureController::DoDeviceStoppedOnIOThread() {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
+  device_in_use_ = false;
+  if (state_ == media::VideoCapture::kStopping) {
+    PostStopping();
+  }
+}
+