Rotate frames correctly for back camera

media/capture/video/linux/camera_characteristics.h

+// Copyright 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 <unordered_map>
+#include <vector>
+
+namespace media {
+
+// DeviceInfo can be found in /etc/camera/camera_characteristics.conf on device.
+struct DeviceInfo {

[kcwu, 2016/11/21 07:59:25]

s/DeviceInfo/CameraDeviceInfo/
DeviceInfo seems too general to media namespace.

[wuchengli, 2016/11/22 03:47:06]

+1

[shenghao, 2016/11/24 07:13:04]

Done.

+  static const int LENS_FACING_FRONT = 0;
+  static const int LENS_FACING_BACK = 1;
+  // USB vender id and product id in "pid:vid" format.
+  std::string vid_pid;
+  // Direction the camera faces relative to device screen.
+  uint32_t lens_facing;
+};
+
+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:

[kcwu, 2016/11/21 07:59:24]

Please relax these rules as possible as you can. Otherwise they are easily to
break.
And for required rules, please give enough error log if they don't meet.

[wuchengli, 2016/11/21 08:56:03]

Why relaxing the rules? We don't need the flexibility.

+//  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.
+//  5. lens_facing should be put before any modules for a camera

[wuchengli, 2016/11/22 07:59:34]

As discussed offline, let's remove all these constraints. Use two hashmaps to
store the camera info. The first hashmap maps from camera id to lens facing and
usb bus/port numbers. The second hashmap maps from vid/pid to camera id.

[shenghao, 2016/11/24 07:13:04]

Done.

+//
+// 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();
+
+  // Get camera facing by specifying vid and pid. |model_id| should be formatted

[wuchengli, 2016/11/22 03:47:06]

s/vid/USB vid/

[shenghao, 2016/11/24 07:13:04]

Done.

+  // as "vid:pid".
+  // Returns DeviceInfo::LENS_FACING_FRONT or DeviceInfo::LENS_FACING_BACK.
+  // Default is DeviceInfo::LENS_FACING_FRONT.
+  int GetCameraFacing(const std::string& model_id);
+
+ private:
+  std::unordered_map<std::string, DeviceInfo> GetDeviceInfoFromFile();
+};
+
+}  // namespace arc
+
+#endif  // MEDIA_CAPTURE_VIDEO_LINUX_CAMERA_CHARACTERISTICS_H_