Repo created

TMessagesProj/jni/voip/webrtc/video/buffered_frame_decryptor.h

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+/*
+ *  Copyright (c) 2018 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef VIDEO_BUFFERED_FRAME_DECRYPTOR_H_
+#define VIDEO_BUFFERED_FRAME_DECRYPTOR_H_
+
+#include <deque>
+#include <memory>
+
+#include "api/crypto/crypto_options.h"
+#include "api/crypto/frame_decryptor_interface.h"
+#include "api/field_trials_view.h"
+#include "modules/rtp_rtcp/source/frame_object.h"
+
+namespace webrtc {
+
+// This callback is provided during the construction of the
+// BufferedFrameDecryptor and is called each time a frame is sucessfully
+// decrypted by the buffer.
+class OnDecryptedFrameCallback {
+ public:
+  virtual ~OnDecryptedFrameCallback() = default;
+  // Called each time a decrypted frame is returned.
+  virtual void OnDecryptedFrame(std::unique_ptr<RtpFrameObject> frame) = 0;
+};
+
+// This callback is called each time there is a status change in the decryption
+// stream. For example going from a none state to a first decryption or going
+// frome a decryptable state to a non decryptable state.
+class OnDecryptionStatusChangeCallback {
+ public:
+  virtual ~OnDecryptionStatusChangeCallback() = default;
+  // Called each time the decryption stream status changes. This call is
+  // blocking so the caller must relinquish the callback quickly. This status
+  // must match what is specified in the FrameDecryptorInterface file. Notably
+  // 0 must indicate success and any positive integer is a failure.
+  virtual void OnDecryptionStatusChange(
+      FrameDecryptorInterface::Status status) = 0;
+};
+
+// The BufferedFrameDecryptor is responsible for deciding when to pass
+// decrypted received frames onto the OnDecryptedFrameCallback. Frames can be
+// delayed when frame encryption is enabled but the key hasn't arrived yet. In
+// this case we stash about 1 second of encrypted frames instead of dropping
+// them to prevent re-requesting the key frame. This optimization is
+// particularly important on low bandwidth networks. Note stashing is only ever
+// done if we have never sucessfully decrypted a frame before. After the first
+// successful decryption payloads will never be stashed.
+class BufferedFrameDecryptor final {
+ public:
+  // Constructs a new BufferedFrameDecryptor that can hold
+  explicit BufferedFrameDecryptor(
+      OnDecryptedFrameCallback* decrypted_frame_callback,
+      OnDecryptionStatusChangeCallback* decryption_status_change_callback,
+      const FieldTrialsView& field_trials);
+
+  ~BufferedFrameDecryptor();
+  // This object cannot be copied.
+  BufferedFrameDecryptor(const BufferedFrameDecryptor&) = delete;
+  BufferedFrameDecryptor& operator=(const BufferedFrameDecryptor&) = delete;
+
+  // Sets a new frame decryptor as the decryptor for the buffered frame
+  // decryptor. This allows the decryptor to be switched out without resetting
+  // the video stream.
+  void SetFrameDecryptor(
+      rtc::scoped_refptr<FrameDecryptorInterface> frame_decryptor);
+
+  // Determines whether the frame should be stashed, dropped or handed off to
+  // the OnDecryptedFrameCallback.
+  void ManageEncryptedFrame(std::unique_ptr<RtpFrameObject> encrypted_frame);
+
+ private:
+  // Represents what should be done with a given frame.
+  enum class FrameDecision { kStash, kDecrypted, kDrop };
+
+  // Attempts to decrypt the frame, if it fails and no prior frames have been
+  // decrypted it will return kStash. Otherwise fail to decrypts will return
+  // kDrop. Successful decryptions will always return kDecrypted.
+  FrameDecision DecryptFrame(RtpFrameObject* frame);
+  // Retries all the stashed frames this is triggered each time a kDecrypted
+  // event occurs.
+  void RetryStashedFrames();
+
+  static const size_t kMaxStashedFrames = 24;
+
+  const bool generic_descriptor_auth_experiment_;
+  bool first_frame_decrypted_ = false;
+  FrameDecryptorInterface::Status last_status_ =
+      FrameDecryptorInterface::Status::kUnknown;
+  rtc::scoped_refptr<FrameDecryptorInterface> frame_decryptor_;
+  OnDecryptedFrameCallback* const decrypted_frame_callback_;
+  OnDecryptionStatusChangeCallback* const decryption_status_change_callback_;
+  std::deque<std::unique_ptr<RtpFrameObject>> stashed_frames_;
+};
+
+}  // namespace webrtc
+
+#endif  // VIDEO_BUFFERED_FRAME_DECRYPTOR_H_