Reland of rotate frames correctly for back camera

media/capture/video/linux/video_capture_device_chromeos.cc

 // 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/capture/video/linux/video_capture_device_chromeos.h"
 
 #include <stdint.h>
 
 #include "base/bind.h"
+#include "base/lazy_instance.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/single_thread_task_runner.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "ui/display/display.h"
 #include "ui/display/display_observer.h"
 #include "ui/display/screen.h"
 
 namespace media {
 
+namespace {
+
+base::LazyInstance<CameraFacingChromeOS>::Leaky g_camera_facing_ =
+    LAZY_INSTANCE_INITIALIZER;
+
+}  // namespace
+
 // This is a delegate class used to transfer Display change events from the UI
 // thread to the media thread.
 class VideoCaptureDeviceChromeOS::ScreenObserverDelegate
     : public display::DisplayObserver,
       public base::RefCountedThreadSafe<ScreenObserverDelegate> {
  public:
   ScreenObserverDelegate(
       VideoCaptureDeviceChromeOS* capture_device,
       scoped_refptr<base::SingleThreadTaskRunner> ui_task_runner)
       : capture_device_(capture_device),
@@ skipping 62 matching lines @@
   scoped_refptr<base::SingleThreadTaskRunner> ui_task_runner_;
   scoped_refptr<base::SingleThreadTaskRunner> capture_task_runner_;
   DISALLOW_IMPLICIT_CONSTRUCTORS(ScreenObserverDelegate);
 };
 
 VideoCaptureDeviceChromeOS::VideoCaptureDeviceChromeOS(
     scoped_refptr<base::SingleThreadTaskRunner> ui_task_runner,
     const VideoCaptureDeviceDescriptor& device_descriptor)
     : VideoCaptureDeviceLinux(device_descriptor),
       screen_observer_delegate_(
-          new ScreenObserverDelegate(this, ui_task_runner)) {}
+          new ScreenObserverDelegate(this, ui_task_runner)),
+      lens_facing_(
+          g_camera_facing_.Get().GetCameraFacing(device_descriptor.device_id,
+                                                 device_descriptor.model_id)) {}
 
 VideoCaptureDeviceChromeOS::~VideoCaptureDeviceChromeOS() {
   screen_observer_delegate_->RemoveObserver();
 }
 
+void VideoCaptureDeviceChromeOS::SetRotation(int rotation) {
+  // We assume external camera is facing the users. If not, the users can
+  // rotate the camera manually by themselves.
+  if (lens_facing_ == CameraFacingChromeOS::LensFacing::BACK) {
+    // Original frame when |rotation| = 0
+    // -----------------------
+    // |          *          |
+    // |         * *         |
+    // |        *   *        |
+    // |       *******       |
+    // |      *       *      |
+    // |     *         *     |
+    // -----------------------
+    //
+    // |rotation| = 90, this is what back camera sees
+    // -----------------------
+    // |    ********         |
+    // |       *   ****      |
+    // |       *      ***    |
+    // |       *      ***    |
+    // |       *   ****      |
+    // |    ********         |
+    // -----------------------
+    //
+    // |rotation| = 90, this is what front camera sees
+    // -----------------------
+    // |         ********    |
+    // |      ****   *       |
+    // |    ***      *       |
+    // |    ***      *       |
+    // |      ****   *       |
+    // |         ********    |
+    // -----------------------
+    //
+    // Therefore, for back camera, we need to rotate (360 - |rotation|).
+    rotation = (360 - rotation) % 360;
+  }
+  VideoCaptureDeviceLinux::SetRotation(rotation);
+}
+
 void VideoCaptureDeviceChromeOS::SetDisplayRotation(
     const display::Display& display) {
   if (display.IsInternal())
     SetRotation(display.rotation() * 90);
 }
 
 }  // namespace media