Rotate frames correctly for back camera

media/capture/video/linux/camera_characteristics.h

+// Copyright (c) 2016 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_CAPTURE_VIDEO_LINUX_CAMERA_CHARACTERISTICS_H_
+#define MEDIA_CAPTURE_VIDEO_LINUX_CAMERA_CHARACTERISTICS_H_
+
+#include <stddef.h>
+#include <string>
+#include <vector>
+
+namespace media {
+

[wuchengli, 2016/11/16 12:15:19]

Document where we can find the definition of lens_facing and sensor_orientation.
Is it camera_metadata.h?

[shenghao, 2016/11/17 08:41:44]

Done.

+struct DeviceInfo {
+  std::string device_path;

[wuchengli, 2016/11/16 12:15:19]

Give an example of device_path.

[shenghao, 2016/11/17 08:41:44]

Done.

+  std::string usb_vid;  // USB vender id
+  std::string usb_pid;  // USB product id
+  uint32_t
+      lens_facing;  // Direction the camera faces relative to device screen.
+  // Clockwise angle through which the output image needs to be rotated to be
+  // upright on the device screen in its native orientation.
+  int32_t sensor_orientation;
+  uint32_t frames_to_skip_after_streamon;

[wuchengli, 2016/11/16 12:15:19]

Document frames_to_skip_after_streamon.

[shenghao, 2016/11/17 08:41:44]

Done.

+  float horizontal_view_angle_16_9;
+  float horizontal_view_angle_4_3;
+  std::vector<float> lens_info_available_focal_lengths;
+  float lens_info_minimum_focus_distance;
+  float lens_info_optimal_focus_distance;
+  float vertical_view_angle_16_9;
+  float vertical_view_angle_4_3;
+};
+
+typedef std::vector<DeviceInfo> DeviceInfos;
+
+// CameraCharacteristics reads the file /etc/camera/camera_characteristics.conf
+// and stores the content in |device_infos_|. There are several assumptions of
+// the config file:
+//  1. Each line should be at most 256 characters long.
+//  2. camera id should be in ascending order (i.e., 0, 1, 2, ...).
+//  3. usb_vid_pid should be the first subkey.
+//  4. All configs of a module should be put together.
+//
+// Example of the config file:
+//  camera0.lens_facing=0
+//  camera0.sensor_orientation=0
+//  camera0.module0.usb_vid_pid=0123:4567
+//  camera0.module0.horizontal_view_angle=68.4
+//  camera0.module0.lens_info_available_focal_lengths=1.64
+//  camera0.module0.lens_info_minimum_focus_distance=0.22
+//  camera0.module0.lens_info_optimal_focus_distance=0.5
+//  camera0.module0.vertical_view_angle=41.6
+//  camera0.module1.usb_vid_pid=89ab:cdef
+//  camera0.module1.lens_info_available_focal_lengths=1.69,2
+//  camera1.lens_facing=1
+//  camera1.sensor_orientation=180
+class CameraCharacteristics {
+ public:
+  CameraCharacteristics();
+  ~CameraCharacteristics();
+
+  // Parses /etc/camera/camera_characteristics.conf.
+  // Returns DeviceInfos with default characteristics if the config file doesn't
+  // exist.
+  const DeviceInfos GetCharacteristicsFromFile(
+      const std::vector<std::string>& devices);
+
+  // Get camera facing by specifying vid and pid. |model_id| should be formatted
+  // as "vid:pid".
+  // Returns 0 as front facing and 1 as back facing. Default is 0.
+  int GetCameraFacing(const std::string& model_id);
+
+ private:
+  DeviceInfos device_infos_;
+
+  void AddPerCameraCharacteristic(uint32_t camera_id,
+                                  const char* characteristic,
+                                  const char* value);
+  void AddPerModuleCharacteristic(uint32_t camera_id,
+                                  const char* characteristic,
+                                  const char* value);
+  void AddFloatValue(const char* value,
+                     const char* characteristic_name,
+                     float* characteristic);
+};
+
+}  // namespace arc
+
+#endif  // MEDIA_CAPTURE_VIDEO_LINUX_CAMERA_CHARACTERISTICS_H_