Rotate frames correctly for back camera

media/capture/video/linux/camera_characteristics.cc

+// 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.
+
+#include "camera_characteristics.h"
+
+#include <base/files/file_util.h>
+#include <base/logging.h>
+#include <base/strings/stringprintf.h>
+#include <base/strings/string_number_conversions.h>
+#include <base/strings/string_piece.h>
+#include <base/strings/string_split.h>
+#include <base/strings/string_util.h>
+
+namespace media {
+
+// /etc/camera/camera_characteristics.conf contains camera information which
+// driver cannot provide.
+static const char kCameraCharacteristicsConfigFile[] =
+    "/etc/camera/camera_characteristics.conf";
+static const char kLensFacing[] = "lens_facing";
+static const char kUsbVidPid[] = "usb_vid_pid";
+static const char kUsbPath[] = "usb_path";
+
+CameraCharacteristics::CameraCharacteristics() {
+  InitializeDeviceInfo();
+}
+
+CameraCharacteristics::~CameraCharacteristics() {}
+
+CameraDeviceInfo::LensFacing CameraCharacteristics::GetCameraFacing(
+    const std::string& device_id,
+    const std::string& model_id) const {
+  std::string usb_id = GetUsbId(device_id);
+  const auto& usb_id_to_camera_id_const = usb_id_to_camera_id_;
+  const auto& model_id_to_camera_id_const = model_id_to_camera_id_;
+  const auto& camera_id_to_facing_const = camera_id_to_facing_;
+  auto usb_id_iter = usb_id_to_camera_id_const.find(usb_id);
+  int camera_id;
+  if (usb_id_iter == usb_id_to_camera_id_const.end()) {
+    // Can't find Usb ID. Fall back to use model_id.
+    auto model_id_iter = model_id_to_camera_id_const.find(model_id);
+    if (model_id_iter == model_id_to_camera_id_const.end()) {
+      LOG(ERROR) << "Can't find model ID in config file: " << model_id;
+      return CameraDeviceInfo::kLensFacingDefault;
+    }
+    camera_id = model_id_iter->second;
+  } else {
+    camera_id = usb_id_iter->second;
+  }
+
+  auto camera_id_iter = camera_id_to_facing_const.find(camera_id);
+  if (camera_id_iter == camera_id_to_facing_const.end()) {
+    LOG(ERROR) << "Can't find lens_facing of camera ID " << camera_id
+               << " in config file";
+    return CameraDeviceInfo::kLensFacingDefault;
+  }
+  return camera_id_iter->second;
+}
+
+std::string CameraCharacteristics::GetUsbId(
+    const std::string& device_id) const {
+  // |device_id| is of the form "/dev/video2".  We want to retrieve "video2"
+  // into |file_name|.
+  const std::string device_dir = "/dev/";
+  DCHECK(base::StartsWith(device_id, device_dir, base::CompareCase::SENSITIVE));
+  const std::string file_name = device_id.substr(device_dir.length());
+
+  // Usb ID can be obtained by "readlink /sys/class/video4linux/video2/device".
+  const std::string symlink =
+      base::StringPrintf("/sys/class/video4linux/%s/device", file_name.c_str());
+  base::FilePath symlinkTarget;
+  if (!base::ReadSymbolicLink(base::FilePath(symlink), &symlinkTarget)) {
+    LOG(ERROR) << "Failed to readlink: " << symlink;
+    return std::string();
+  }
+
+  // |symlinkTarget| is of the format "../../../A-B:C.D". Remove the path
+  // prefix.
+  base::StringPiece usb_part = symlinkTarget.BaseName().value();
+
+  // |usb_part| is of the format "A-B:C.D" or "A-B.C:D". We want everything
+  // before ":".
+  std::vector<base::StringPiece> usb_id_pieces = base::SplitStringPiece(
+      usb_part, ":", base::WhitespaceHandling::TRIM_WHITESPACE,
+      base::SplitResult::SPLIT_WANT_ALL);
+
+  if (usb_id_pieces.empty()) {
+    LOG(ERROR) << "Error after split: " << usb_part;
+    return std::string();
+  }
+  return usb_id_pieces[0].as_string();
+}
+
+bool CameraCharacteristics::GetCameraId(const base::StringPiece& sub_key,
+                                        int* camera_id) {
+  const base::StringPiece camera_id_prefix = "camera";
+  if (!sub_key.starts_with(camera_id_prefix)) {
+    return false;
+  }

[mcasas, 2016/11/29 19:12:55]

No {} for one line bodies.

[shenghao, 2016/12/01 07:34:21]

Done.

+  return base::StringToInt(sub_key.substr(camera_id_prefix.size()), camera_id);
+}
+
+void CameraCharacteristics::InitializeDeviceInfo() {
+  const base::FilePath path(kCameraCharacteristicsConfigFile);
+  std::string content;
+  if (!base::ReadFileToString(path, &content)) {
+    DVLOG(1) << "ReadFileToString fails";

[mcasas, 2016/11/29 19:12:55]

This should be DLOG() and, for more info, I'd consider
DPLOG() that pastes the last system error as string afterwards.

Also, s/LOG/DLOG/ elsewhere in this file, and consider
DPLOG(ERROR) instead.

[shenghao, 2016/12/01 07:34:21]

Done.

+    return;
+  }
+  std::vector<base::StringPiece> lines = base::SplitStringPiece(
+      content, "\n", base::WhitespaceHandling::TRIM_WHITESPACE,
+      base::SplitResult::SPLIT_WANT_NONEMPTY);
+
+  for (base::StringPiece line : lines) {
+    if (line.starts_with("#")) {
+      // Ignore the comments that starts with "#".
+      continue;
+    }
+    std::vector<base::StringPiece> key_value = base::SplitStringPiece(
+        line, "=", base::WhitespaceHandling::TRIM_WHITESPACE,
+        base::SplitResult::SPLIT_WANT_ALL);
+    if (key_value.size() != 2) {
+      LOG(ERROR) << "Invalid line in config file: " << line;
+      continue;
+    }
+    const auto& key = key_value[0];
+    const auto& value = key_value[1];
+    std::vector<base::StringPiece> sub_keys = base::SplitStringPiece(
+        key, ".", base::WhitespaceHandling::TRIM_WHITESPACE,
+        base::SplitResult::SPLIT_WANT_ALL);
+
+    int camera_id = 0;
+    if (sub_keys.size() >= 1) {
+      if (!GetCameraId(sub_keys[0], &camera_id)) {
+        LOG(ERROR) << "Invalid sub key for camera id: " << sub_keys[0];
+        continue;
+      }
+    } else {
+      LOG(ERROR) << "No valid sub key exists. Line format is invalid: " << line;
+      continue;
+    }
+    if (sub_keys.size() == 2 && sub_keys[1] == kLensFacing) {
+      int lens_facing = static_cast<int>(CameraDeviceInfo::kLensFacingDefault);
+      if (!base::StringToInt(value, &lens_facing) ||
+          lens_facing <
+              static_cast<int>(CameraDeviceInfo::LensFacing::kFront) ||
+          lens_facing > static_cast<int>(CameraDeviceInfo::LensFacing::kBack)) {

[mcasas, 2016/11/29 19:12:55]

No casting enum class members to int or viceversa,
instead, use a switch.

[shenghao, 2016/12/01 07:34:21]

Done.

+        LOG(ERROR) << "Invalid value for lens_facing: " << value;
+        continue;
+      }
+      camera_id_to_facing_[camera_id] =
+          static_cast<CameraDeviceInfo::LensFacing>(lens_facing);
+    } else if (sub_keys.size() == 3 && sub_keys[2] == kUsbVidPid) {
+      if (value.empty()) {
+        LOG(ERROR) << "model_id is empty";
+        continue;
+      }
+      model_id_to_camera_id_[value.as_string()] = camera_id;
+    } else if (sub_keys.size() == 3 && sub_keys[2] == kUsbPath) {
+      if (value.empty()) {
+        LOG(ERROR) << "usb_path is empty";
+        continue;
+      }
+      usb_id_to_camera_id_[value.as_string()] = camera_id;
+    }
+    // Ignore unknown or unutilized attributes.
+  }
+}
+
+}  // namespace media