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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.
#include <deque>
#include <memory>
#include "api/crypto/crypto_options.h"
#include "api/crypto/frame_decryptor_interface.h"
#include "modules/include/module_common_types.h"
#include "modules/video_coding/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 {
virtual ~OnDecryptedFrameCallback() = default;
// Called each time a decrypted frame is returned.
virtual void OnDecryptedFrame(
std::unique_ptr<video_coding::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 {
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 {
// Constructs a new BufferedFrameDecryptor that can hold
explicit BufferedFrameDecryptor(
OnDecryptedFrameCallback* decrypted_frame_callback,
OnDecryptionStatusChangeCallback* decryption_status_change_callback);
// 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<video_coding::RtpFrameObject> encrypted_frame);
// 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(video_coding::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_ =
rtc::scoped_refptr<FrameDecryptorInterface> frame_decryptor_;
OnDecryptedFrameCallback* const decrypted_frame_callback_;
OnDecryptionStatusChangeCallback* const decryption_status_change_callback_;
std::deque<std::unique_ptr<video_coding::RtpFrameObject>> stashed_frames_;
} // namespace webrtc