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+/*
+ *  Copyright (c) 2015 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 CALL_BITRATE_ALLOCATOR_H_
+#define CALL_BITRATE_ALLOCATOR_H_
+
+#include <stdint.h>
+
+#include <map>
+#include <memory>
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "api/call/bitrate_allocation.h"
+#include "api/sequence_checker.h"
+#include "api/transport/network_types.h"
+#include "rtc_base/system/no_unique_address.h"
+
+namespace webrtc {
+
+class Clock;
+
+// Used by all send streams with adaptive bitrate, to get the currently
+// allocated bitrate for the send stream. The current network properties are
+// given at the same time, to let the send stream decide about possible loss
+// protection.
+class BitrateAllocatorObserver {
+ public:
+  // Returns the amount of protection used by the BitrateAllocatorObserver
+  // implementation, as bitrate in bps.
+  virtual uint32_t OnBitrateUpdated(BitrateAllocationUpdate update) = 0;
+
+ protected:
+  virtual ~BitrateAllocatorObserver() {}
+};
+
+// Struct describing parameters for how a media stream should get bitrate
+// allocated to it.
+
+struct MediaStreamAllocationConfig {
+  // Minimum bitrate supported by track. 0 equals no min bitrate.
+  uint32_t min_bitrate_bps;
+  // Maximum bitrate supported by track. 0 equals no max bitrate.
+  uint32_t max_bitrate_bps;
+  uint32_t pad_up_bitrate_bps;
+  int64_t priority_bitrate_bps;
+  // True means track may not be paused by allocating 0 bitrate will allocate at
+  // least `min_bitrate_bps` for this observer, even if the BWE is too low,
+  // false will allocate 0 to the observer if BWE doesn't allow
+  // `min_bitrate_bps`.
+  bool enforce_min_bitrate;
+  // The amount of bitrate allocated to this observer relative to all other
+  // observers. If an observer has twice the bitrate_priority of other
+  // observers, it should be allocated twice the bitrate above its min.
+  double bitrate_priority;
+};
+
+// Interface used for mocking
+class BitrateAllocatorInterface {
+ public:
+  virtual void AddObserver(BitrateAllocatorObserver* observer,
+                           MediaStreamAllocationConfig config) = 0;
+  virtual void RemoveObserver(BitrateAllocatorObserver* observer) = 0;
+  virtual int GetStartBitrate(BitrateAllocatorObserver* observer) const = 0;
+
+ protected:
+  virtual ~BitrateAllocatorInterface() = default;
+};
+
+namespace bitrate_allocator_impl {
+struct AllocatableTrack {
+  AllocatableTrack(BitrateAllocatorObserver* observer,
+                   MediaStreamAllocationConfig allocation_config)
+      : observer(observer),
+        config(allocation_config),
+        allocated_bitrate_bps(-1),
+        media_ratio(1.0) {}
+  BitrateAllocatorObserver* observer;
+  MediaStreamAllocationConfig config;
+  int64_t allocated_bitrate_bps;
+  double media_ratio;  // Part of the total bitrate used for media [0.0, 1.0].
+
+  uint32_t LastAllocatedBitrate() const;
+  // The minimum bitrate required by this observer, including
+  // enable-hysteresis if the observer is in a paused state.
+  uint32_t MinBitrateWithHysteresis() const;
+};
+}  // namespace bitrate_allocator_impl
+
+// Usage: this class will register multiple RtcpBitrateObserver's one at each
+// RTCP module. It will aggregate the results and run one bandwidth estimation
+// and push the result to the encoders via BitrateAllocatorObserver(s).
+class BitrateAllocator : public BitrateAllocatorInterface {
+ public:
+  // Used to get notified when send stream limits such as the minimum send
+  // bitrate and max padding bitrate is changed.
+  class LimitObserver {
+   public:
+    virtual void OnAllocationLimitsChanged(BitrateAllocationLimits limits) = 0;
+
+   protected:
+    virtual ~LimitObserver() = default;
+  };
+
+  explicit BitrateAllocator(LimitObserver* limit_observer);
+  ~BitrateAllocator() override;
+
+  void UpdateStartRate(uint32_t start_rate_bps);
+
+  // Allocate target_bitrate across the registered BitrateAllocatorObservers.
+  void OnNetworkEstimateChanged(TargetTransferRate msg);
+
+  // Set the configuration used by the bandwidth management.
+  // `observer` updates bitrates if already in use.
+  // `config` is the configuration to use for allocation.
+  // Note that `observer`->OnBitrateUpdated() will be called
+  // within the scope of this method with the current rtt, fraction_loss and
+  // available bitrate and that the bitrate in OnBitrateUpdated will be zero if
+  // the `observer` is currently not allowed to send data.
+  void AddObserver(BitrateAllocatorObserver* observer,
+                   MediaStreamAllocationConfig config) override;
+
+  // Removes a previously added observer, but will not trigger a new bitrate
+  // allocation.
+  void RemoveObserver(BitrateAllocatorObserver* observer) override;
+
+  // Returns initial bitrate allocated for `observer`. If `observer` is not in
+  // the list of added observers, a best guess is returned.
+  int GetStartBitrate(BitrateAllocatorObserver* observer) const override;
+
+ private:
+  using AllocatableTrack = bitrate_allocator_impl::AllocatableTrack;
+
+  // Calculates the minimum requested send bitrate and max padding bitrate and
+  // calls LimitObserver::OnAllocationLimitsChanged.
+  void UpdateAllocationLimits() RTC_RUN_ON(&sequenced_checker_);
+
+  // Allow packets to be transmitted in up to 2 times max video bitrate if the
+  // bandwidth estimate allows it.
+  // TODO(bugs.webrtc.org/8541): May be worth to refactor to keep this logic in
+  // video send stream.
+  static uint8_t GetTransmissionMaxBitrateMultiplier();
+
+  RTC_NO_UNIQUE_ADDRESS SequenceChecker sequenced_checker_;
+  LimitObserver* const limit_observer_ RTC_GUARDED_BY(&sequenced_checker_);
+  // Stored in a list to keep track of the insertion order.
+  std::vector<AllocatableTrack> allocatable_tracks_
+      RTC_GUARDED_BY(&sequenced_checker_);
+  uint32_t last_target_bps_ RTC_GUARDED_BY(&sequenced_checker_);
+  uint32_t last_stable_target_bps_ RTC_GUARDED_BY(&sequenced_checker_);
+  uint32_t last_non_zero_bitrate_bps_ RTC_GUARDED_BY(&sequenced_checker_);
+  uint8_t last_fraction_loss_ RTC_GUARDED_BY(&sequenced_checker_);
+  int64_t last_rtt_ RTC_GUARDED_BY(&sequenced_checker_);
+  int64_t last_bwe_period_ms_ RTC_GUARDED_BY(&sequenced_checker_);
+  // Number of mute events based on too low BWE, not network up/down.
+  int num_pause_events_ RTC_GUARDED_BY(&sequenced_checker_);
+  int64_t last_bwe_log_time_ RTC_GUARDED_BY(&sequenced_checker_);
+  BitrateAllocationLimits current_limits_ RTC_GUARDED_BY(&sequenced_checker_);
+};
+
+}  // namespace webrtc
+#endif  // CALL_BITRATE_ALLOCATOR_H_