Line data    Source code

       1             : /*
       2             :  *  Copyright 2016 The WebRTC project authors. All Rights Reserved.
       3             :  *
       4             :  *  Use of this source code is governed by a BSD-style license
       5             :  *  that can be found in the LICENSE file in the root of the source
       6             :  *  tree. An additional intellectual property rights grant can be found
       7             :  *  in the file PATENTS.  All contributing project authors may
       8             :  *  be found in the AUTHORS file in the root of the source tree.
       9             :  */
      10             : 
      11             : #ifndef WEBRTC_COMMON_VIDEO_INCLUDE_BITRATE_ADJUSTER_H_
      12             : #define WEBRTC_COMMON_VIDEO_INCLUDE_BITRATE_ADJUSTER_H_
      13             : 
      14             : #include <functional>
      15             : 
      16             : #include "webrtc/base/criticalsection.h"
      17             : #include "webrtc/base/rate_statistics.h"
      18             : 
      19             : namespace webrtc {
      20             : 
      21             : class Clock;
      22             : 
      23             : // Certain hardware encoders tend to consistently overshoot the bitrate that
      24             : // they are configured to encode at. This class estimates an adjusted bitrate
      25             : // that when set on the encoder will produce the desired bitrate.
      26             : class BitrateAdjuster {
      27             :  public:
      28             :   // min_adjusted_bitrate_pct and max_adjusted_bitrate_pct are the lower and
      29             :   // upper bound outputted adjusted bitrates as a percentage of the target
      30             :   // bitrate.
      31             :   BitrateAdjuster(Clock* clock,
      32             :                   float min_adjusted_bitrate_pct,
      33             :                   float max_adjusted_bitrate_pct);
      34           0 :   virtual ~BitrateAdjuster() {}
      35             : 
      36             :   static const uint32_t kBitrateUpdateIntervalMs;
      37             :   static const uint32_t kBitrateUpdateFrameInterval;
      38             :   static const float kBitrateTolerancePct;
      39             :   static const float kBytesPerMsToBitsPerSecond;
      40             : 
      41             :   // Sets the desired bitrate in bps (bits per second).
      42             :   // Should be called at least once before Update.
      43             :   void SetTargetBitrateBps(uint32_t bitrate_bps);
      44             :   uint32_t GetTargetBitrateBps() const;
      45             : 
      46             :   // Returns the adjusted bitrate in bps.
      47             :   uint32_t GetAdjustedBitrateBps() const;
      48             : 
      49             :   // Returns what we think the current bitrate is.
      50             :   rtc::Optional<uint32_t> GetEstimatedBitrateBps();
      51             : 
      52             :   // This should be called after each frame is encoded. The timestamp at which
      53             :   // it is called is used to estimate the output bitrate of the encoder.
      54             :   // Should be called from only one thread.
      55             :   void Update(size_t frame_size);
      56             : 
      57             :  private:
      58             :   // Returns true if the bitrate is within kBitrateTolerancePct of bitrate_bps.
      59             :   bool IsWithinTolerance(uint32_t bitrate_bps, uint32_t target_bitrate_bps);
      60             : 
      61             :   // Returns smallest possible adjusted value.
      62             :   uint32_t GetMinAdjustedBitrateBps() const EXCLUSIVE_LOCKS_REQUIRED(crit_);
      63             :   // Returns largest possible adjusted value.
      64             :   uint32_t GetMaxAdjustedBitrateBps() const EXCLUSIVE_LOCKS_REQUIRED(crit_);
      65             : 
      66             :   void Reset();
      67             :   void UpdateBitrate(uint32_t current_time_ms) EXCLUSIVE_LOCKS_REQUIRED(crit_);
      68             : 
      69             :   rtc::CriticalSection crit_;
      70             :   Clock* const clock_;
      71             :   const float min_adjusted_bitrate_pct_;
      72             :   const float max_adjusted_bitrate_pct_;
      73             :   // The bitrate we want.
      74             :   volatile uint32_t target_bitrate_bps_ GUARDED_BY(crit_);
      75             :   // The bitrate we use to get what we want.
      76             :   volatile uint32_t adjusted_bitrate_bps_ GUARDED_BY(crit_);
      77             :   // The target bitrate that the adjusted bitrate was computed from.
      78             :   volatile uint32_t last_adjusted_target_bitrate_bps_ GUARDED_BY(crit_);
      79             :   // Used to estimate bitrate.
      80             :   RateStatistics bitrate_tracker_ GUARDED_BY(crit_);
      81             :   // The last time we tried to adjust the bitrate.
      82             :   uint32_t last_bitrate_update_time_ms_ GUARDED_BY(crit_);
      83             :   // The number of frames since the last time we tried to adjust the bitrate.
      84             :   uint32_t frames_since_last_update_ GUARDED_BY(crit_);
      85             : };
      86             : 
      87             : }  // namespace webrtc
      88             : 
      89             : #endif  // WEBRTC_COMMON_VIDEO_INCLUDE_BITRATE_ADJUSTER_H_