webrtc/modules/video_coding/utility/frame_dropper.cc - platform/external/webrtc - Git at Google

 /*
  *  Copyright (c) 2011 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 "webrtc/modules/video_coding/utility/frame_dropper.h"

 #include "webrtc/system_wrappers/include/trace.h"

 namespace webrtc {

 const float kDefaultKeyFrameSizeAvgKBits = 0.9f;
 const float kDefaultKeyFrameRatio = 0.99f;
 const float kDefaultDropRatioAlpha = 0.9f;
 const float kDefaultDropRatioMax = 0.96f;
 const float kDefaultMaxTimeToDropFrames = 4.0f;  // In seconds.

 FrameDropper::FrameDropper()
     : _keyFrameSizeAvgKbits(kDefaultKeyFrameSizeAvgKBits),
       _keyFrameRatio(kDefaultKeyFrameRatio),
       _dropRatio(kDefaultDropRatioAlpha, kDefaultDropRatioMax),
       _enabled(true),
       _max_time_drops(kDefaultMaxTimeToDropFrames) {
   Reset();
 }

 FrameDropper::FrameDropper(float max_time_drops)
     : _keyFrameSizeAvgKbits(kDefaultKeyFrameSizeAvgKBits),
       _keyFrameRatio(kDefaultKeyFrameRatio),
       _dropRatio(kDefaultDropRatioAlpha, kDefaultDropRatioMax),
       _enabled(true),
       _max_time_drops(max_time_drops) {
   Reset();
 }

 void FrameDropper::Reset() {
   _keyFrameRatio.Reset(0.99f);
   _keyFrameRatio.Apply(
       1.0f, 1.0f / 300.0f);  // 1 key frame every 10th second in 30 fps
   _keyFrameSizeAvgKbits.Reset(0.9f);
   _keyFrameCount = 0;
   _accumulator = 0.0f;
   _accumulatorMax = 150.0f;  // assume 300 kb/s and 0.5 s window
   _targetBitRate = 300.0f;
   _incoming_frame_rate = 30;
   _keyFrameSpreadFrames = 0.5f * _incoming_frame_rate;
   _dropNext = false;
   _dropRatio.Reset(0.9f);
   _dropRatio.Apply(0.0f, 0.0f);  // Initialize to 0
   _dropCount = 0;
   _windowSize = 0.5f;
   _wasBelowMax = true;
   _fastMode = false;  // start with normal (non-aggressive) mode
   // Cap for the encoder buffer level/accumulator, in secs.
   _cap_buffer_size = 3.0f;
   // Cap on maximum amount of dropped frames between kept frames, in secs.
   _max_time_drops = 4.0f;
 }

 void FrameDropper::Enable(bool enable) {
   _enabled = enable;
 }

 void FrameDropper::Fill(size_t frameSizeBytes, bool deltaFrame) {
   if (!_enabled) {
     return;
   }
   float frameSizeKbits = 8.0f * static_cast<float>(frameSizeBytes) / 1000.0f;
   if (!deltaFrame &&
       !_fastMode) {  // fast mode does not treat key-frames any different
     _keyFrameSizeAvgKbits.Apply(1, frameSizeKbits);
     _keyFrameRatio.Apply(1.0, 1.0);
     if (frameSizeKbits > _keyFrameSizeAvgKbits.filtered()) {
       // Remove the average key frame size since we
       // compensate for key frames when adding delta
       // frames.
       frameSizeKbits -= _keyFrameSizeAvgKbits.filtered();
     } else {
       // Shouldn't be negative, so zero is the lower bound.
       frameSizeKbits = 0;
     }
     if (_keyFrameRatio.filtered() > 1e-5 &&
         1 / _keyFrameRatio.filtered() < _keyFrameSpreadFrames) {
       // We are sending key frames more often than our upper bound for
       // how much we allow the key frame compensation to be spread
       // out in time. Therefor we must use the key frame ratio rather
       // than keyFrameSpreadFrames.
       _keyFrameCount =
           static_cast<int32_t>(1 / _keyFrameRatio.filtered() + 0.5);
     } else {
       // Compensate for the key frame the following frames
       _keyFrameCount = static_cast<int32_t>(_keyFrameSpreadFrames + 0.5);
     }
   } else {
     // Decrease the keyFrameRatio
     _keyFrameRatio.Apply(1.0, 0.0);
   }
   // Change the level of the accumulator (bucket)
   _accumulator += frameSizeKbits;
   CapAccumulator();
 }

 void FrameDropper::Leak(uint32_t inputFrameRate) {
   if (!_enabled) {
     return;
   }
   if (inputFrameRate < 1) {
     return;
   }
   if (_targetBitRate < 0.0f) {
     return;
   }
   _keyFrameSpreadFrames = 0.5f * inputFrameRate;
   // T is the expected bits per frame (target). If all frames were the same
   // size,
   // we would get T bits per frame. Notice that T is also weighted to be able to
   // force a lower frame rate if wanted.
   float T = _targetBitRate / inputFrameRate;
   if (_keyFrameCount > 0) {
     // Perform the key frame compensation
     if (_keyFrameRatio.filtered() > 0 &&
         1 / _keyFrameRatio.filtered() < _keyFrameSpreadFrames) {
       T -= _keyFrameSizeAvgKbits.filtered() * _keyFrameRatio.filtered();
     } else {
       T -= _keyFrameSizeAvgKbits.filtered() / _keyFrameSpreadFrames;
     }
     _keyFrameCount--;
   }
   _accumulator -= T;
   if (_accumulator < 0.0f) {
     _accumulator = 0.0f;
   }
   UpdateRatio();
 }

 void FrameDropper::UpdateNack(uint32_t nackBytes) {
   if (!_enabled) {
     return;
   }
   _accumulator += static_cast<float>(nackBytes) * 8.0f / 1000.0f;
 }

 void FrameDropper::FillBucket(float inKbits, float outKbits) {
   _accumulator += (inKbits - outKbits);
 }

 void FrameDropper::UpdateRatio() {
   if (_accumulator > 1.3f * _accumulatorMax) {
     // Too far above accumulator max, react faster
     _dropRatio.UpdateBase(0.8f);
   } else {
     // Go back to normal reaction
     _dropRatio.UpdateBase(0.9f);
   }
   if (_accumulator > _accumulatorMax) {
     // We are above accumulator max, and should ideally
     // drop a frame. Increase the dropRatio and drop
     // the frame later.
     if (_wasBelowMax) {
       _dropNext = true;
     }
     if (_fastMode) {
       // always drop in aggressive mode
       _dropNext = true;
     }

     _dropRatio.Apply(1.0f, 1.0f);
     _dropRatio.UpdateBase(0.9f);
   } else {
     _dropRatio.Apply(1.0f, 0.0f);
   }
   _wasBelowMax = _accumulator < _accumulatorMax;
 }

 // This function signals when to drop frames to the caller. It makes use of the
 // dropRatio
 // to smooth out the drops over time.
 bool FrameDropper::DropFrame() {
   if (!_enabled) {
     return false;
   }
   if (_dropNext) {
     _dropNext = false;
     _dropCount = 0;
   }

   if (_dropRatio.filtered() >= 0.5f) {  // Drops per keep
     // limit is the number of frames we should drop between each kept frame
     // to keep our drop ratio. limit is positive in this case.
     float denom = 1.0f - _dropRatio.filtered();
     if (denom < 1e-5) {
       denom = 1e-5f;
     }
     int32_t limit = static_cast<int32_t>(1.0f / denom - 1.0f + 0.5f);
     // Put a bound on the max amount of dropped frames between each kept
     // frame, in terms of frame rate and window size (secs).
     int max_limit = static_cast<int>(_incoming_frame_rate * _max_time_drops);
     if (limit > max_limit) {
       limit = max_limit;
     }
     if (_dropCount < 0) {
       // Reset the _dropCount since it was negative and should be positive.
       if (_dropRatio.filtered() > 0.4f) {
         _dropCount = -_dropCount;
       } else {
         _dropCount = 0;
       }
     }
     if (_dropCount < limit) {
       // As long we are below the limit we should drop frames.
       _dropCount++;
       return true;
     } else {
       // Only when we reset _dropCount a frame should be kept.
       _dropCount = 0;
       return false;
     }
   } else if (_dropRatio.filtered() > 0.0f &&
              _dropRatio.filtered() < 0.5f) {  // Keeps per drop
     // limit is the number of frames we should keep between each drop
     // in order to keep the drop ratio. limit is negative in this case,
     // and the _dropCount is also negative.
     float denom = _dropRatio.filtered();
     if (denom < 1e-5) {
       denom = 1e-5f;
     }
     int32_t limit = -static_cast<int32_t>(1.0f / denom - 1.0f + 0.5f);
     if (_dropCount > 0) {
       // Reset the _dropCount since we have a positive
       // _dropCount, and it should be negative.
       if (_dropRatio.filtered() < 0.6f) {
         _dropCount = -_dropCount;
       } else {
         _dropCount = 0;
       }
     }
     if (_dropCount > limit) {
       if (_dropCount == 0) {
         // Drop frames when we reset _dropCount.
         _dropCount--;
         return true;
       } else {
         // Keep frames as long as we haven't reached limit.
         _dropCount--;
         return false;
       }
     } else {
       _dropCount = 0;
       return false;
     }
   }
   _dropCount = 0;
   return false;

   // A simpler version, unfiltered and quicker
   // bool dropNext = _dropNext;
   // _dropNext = false;
   // return dropNext;
 }

 void FrameDropper::SetRates(float bitRate, float incoming_frame_rate) {
   // Bit rate of -1 means infinite bandwidth.
   _accumulatorMax = bitRate * _windowSize;  // bitRate * windowSize (in seconds)
   if (_targetBitRate > 0.0f && bitRate < _targetBitRate &&
       _accumulator > _accumulatorMax) {
     // Rescale the accumulator level if the accumulator max decreases
     _accumulator = bitRate / _targetBitRate * _accumulator;
   }
   _targetBitRate = bitRate;
   CapAccumulator();
   _incoming_frame_rate = incoming_frame_rate;
 }

 float FrameDropper::ActualFrameRate(uint32_t inputFrameRate) const {
   if (!_enabled) {
     return static_cast<float>(inputFrameRate);
   }
   return inputFrameRate * (1.0f - _dropRatio.filtered());
 }

 // Put a cap on the accumulator, i.e., don't let it grow beyond some level.
 // This is a temporary fix for screencasting where very large frames from
 // encoder will cause very slow response (too many frame drops).
 void FrameDropper::CapAccumulator() {
   float max_accumulator = _targetBitRate * _cap_buffer_size;
   if (_accumulator > max_accumulator) {
     _accumulator = max_accumulator;
   }
 }
 }  // namespace webrtc
	/*
	* Copyright (c) 2011 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 "webrtc/modules/video_coding/utility/frame_dropper.h"

	#include "webrtc/system_wrappers/include/trace.h"

	namespace webrtc {

	const float kDefaultKeyFrameSizeAvgKBits = 0.9f;
	const float kDefaultKeyFrameRatio = 0.99f;
	const float kDefaultDropRatioAlpha = 0.9f;
	const float kDefaultDropRatioMax = 0.96f;
	const float kDefaultMaxTimeToDropFrames = 4.0f; // In seconds.

	FrameDropper::FrameDropper()
	: _keyFrameSizeAvgKbits(kDefaultKeyFrameSizeAvgKBits),
	_keyFrameRatio(kDefaultKeyFrameRatio),
	_dropRatio(kDefaultDropRatioAlpha, kDefaultDropRatioMax),
	_enabled(true),
	_max_time_drops(kDefaultMaxTimeToDropFrames) {
	Reset();
	}

	FrameDropper::FrameDropper(float max_time_drops)
	: _keyFrameSizeAvgKbits(kDefaultKeyFrameSizeAvgKBits),
	_keyFrameRatio(kDefaultKeyFrameRatio),
	_dropRatio(kDefaultDropRatioAlpha, kDefaultDropRatioMax),
	_enabled(true),
	_max_time_drops(max_time_drops) {
	Reset();
	}

	void FrameDropper::Reset() {
	_keyFrameRatio.Reset(0.99f);
	_keyFrameRatio.Apply(
	1.0f, 1.0f / 300.0f); // 1 key frame every 10th second in 30 fps
	_keyFrameSizeAvgKbits.Reset(0.9f);
	_keyFrameCount = 0;
	_accumulator = 0.0f;
	_accumulatorMax = 150.0f; // assume 300 kb/s and 0.5 s window
	_targetBitRate = 300.0f;
	_incoming_frame_rate = 30;
	_keyFrameSpreadFrames = 0.5f * _incoming_frame_rate;
	_dropNext = false;
	_dropRatio.Reset(0.9f);
	_dropRatio.Apply(0.0f, 0.0f); // Initialize to 0
	_dropCount = 0;
	_windowSize = 0.5f;
	_wasBelowMax = true;
	_fastMode = false; // start with normal (non-aggressive) mode
	// Cap for the encoder buffer level/accumulator, in secs.
	_cap_buffer_size = 3.0f;
	// Cap on maximum amount of dropped frames between kept frames, in secs.
	_max_time_drops = 4.0f;
	}

	void FrameDropper::Enable(bool enable) {
	_enabled = enable;
	}

	void FrameDropper::Fill(size_t frameSizeBytes, bool deltaFrame) {
	if (!_enabled) {
	return;
	}
	float frameSizeKbits = 8.0f * static_cast<float>(frameSizeBytes) / 1000.0f;
	if (!deltaFrame &&
	!_fastMode) { // fast mode does not treat key-frames any different
	_keyFrameSizeAvgKbits.Apply(1, frameSizeKbits);
	_keyFrameRatio.Apply(1.0, 1.0);
	if (frameSizeKbits > _keyFrameSizeAvgKbits.filtered()) {
	// Remove the average key frame size since we
	// compensate for key frames when adding delta
	// frames.
	frameSizeKbits -= _keyFrameSizeAvgKbits.filtered();
	} else {
	// Shouldn't be negative, so zero is the lower bound.
	frameSizeKbits = 0;
	}
	if (_keyFrameRatio.filtered() > 1e-5 &&
	1 / _keyFrameRatio.filtered() < _keyFrameSpreadFrames) {
	// We are sending key frames more often than our upper bound for
	// how much we allow the key frame compensation to be spread
	// out in time. Therefor we must use the key frame ratio rather
	// than keyFrameSpreadFrames.
	_keyFrameCount =
	static_cast<int32_t>(1 / _keyFrameRatio.filtered() + 0.5);
	} else {
	// Compensate for the key frame the following frames
	_keyFrameCount = static_cast<int32_t>(_keyFrameSpreadFrames + 0.5);
	}
	} else {
	// Decrease the keyFrameRatio
	_keyFrameRatio.Apply(1.0, 0.0);
	}
	// Change the level of the accumulator (bucket)
	_accumulator += frameSizeKbits;
	CapAccumulator();
	}

	void FrameDropper::Leak(uint32_t inputFrameRate) {
	if (!_enabled) {
	return;
	}
	if (inputFrameRate < 1) {
	return;
	}
	if (_targetBitRate < 0.0f) {
	return;
	}
	_keyFrameSpreadFrames = 0.5f * inputFrameRate;
	// T is the expected bits per frame (target). If all frames were the same
	// size,
	// we would get T bits per frame. Notice that T is also weighted to be able to
	// force a lower frame rate if wanted.
	float T = _targetBitRate / inputFrameRate;
	if (_keyFrameCount > 0) {
	// Perform the key frame compensation
	if (_keyFrameRatio.filtered() > 0 &&
	1 / _keyFrameRatio.filtered() < _keyFrameSpreadFrames) {
	T -= _keyFrameSizeAvgKbits.filtered() * _keyFrameRatio.filtered();
	} else {
	T -= _keyFrameSizeAvgKbits.filtered() / _keyFrameSpreadFrames;
	}
	_keyFrameCount--;
	}
	_accumulator -= T;
	if (_accumulator < 0.0f) {
	_accumulator = 0.0f;
	}
	UpdateRatio();
	}

	void FrameDropper::UpdateNack(uint32_t nackBytes) {
	if (!_enabled) {
	return;
	}
	_accumulator += static_cast<float>(nackBytes) * 8.0f / 1000.0f;
	}

	void FrameDropper::FillBucket(float inKbits, float outKbits) {
	_accumulator += (inKbits - outKbits);
	}

	void FrameDropper::UpdateRatio() {
	if (_accumulator > 1.3f * _accumulatorMax) {
	// Too far above accumulator max, react faster
	_dropRatio.UpdateBase(0.8f);
	} else {
	// Go back to normal reaction
	_dropRatio.UpdateBase(0.9f);
	}
	if (_accumulator > _accumulatorMax) {
	// We are above accumulator max, and should ideally
	// drop a frame. Increase the dropRatio and drop
	// the frame later.
	if (_wasBelowMax) {
	_dropNext = true;
	}
	if (_fastMode) {
	// always drop in aggressive mode
	_dropNext = true;
	}

	_dropRatio.Apply(1.0f, 1.0f);
	_dropRatio.UpdateBase(0.9f);
	} else {
	_dropRatio.Apply(1.0f, 0.0f);
	}
	_wasBelowMax = _accumulator < _accumulatorMax;
	}

	// This function signals when to drop frames to the caller. It makes use of the
	// dropRatio
	// to smooth out the drops over time.
	bool FrameDropper::DropFrame() {
	if (!_enabled) {
	return false;
	}
	if (_dropNext) {
	_dropNext = false;
	_dropCount = 0;
	}

	if (_dropRatio.filtered() >= 0.5f) { // Drops per keep
	// limit is the number of frames we should drop between each kept frame
	// to keep our drop ratio. limit is positive in this case.
	float denom = 1.0f - _dropRatio.filtered();
	if (denom < 1e-5) {
	denom = 1e-5f;
	}
	int32_t limit = static_cast<int32_t>(1.0f / denom - 1.0f + 0.5f);
	// Put a bound on the max amount of dropped frames between each kept
	// frame, in terms of frame rate and window size (secs).
	int max_limit = static_cast<int>(_incoming_frame_rate * _max_time_drops);
	if (limit > max_limit) {
	limit = max_limit;
	}
	if (_dropCount < 0) {
	// Reset the _dropCount since it was negative and should be positive.
	if (_dropRatio.filtered() > 0.4f) {
	_dropCount = -_dropCount;
	} else {
	_dropCount = 0;
	}
	}
	if (_dropCount < limit) {
	// As long we are below the limit we should drop frames.
	_dropCount++;
	return true;
	} else {
	// Only when we reset _dropCount a frame should be kept.
	_dropCount = 0;
	return false;
	}
	} else if (_dropRatio.filtered() > 0.0f &&
	_dropRatio.filtered() < 0.5f) { // Keeps per drop
	// limit is the number of frames we should keep between each drop
	// in order to keep the drop ratio. limit is negative in this case,
	// and the _dropCount is also negative.
	float denom = _dropRatio.filtered();
	if (denom < 1e-5) {
	denom = 1e-5f;
	}
	int32_t limit = -static_cast<int32_t>(1.0f / denom - 1.0f + 0.5f);
	if (_dropCount > 0) {
	// Reset the _dropCount since we have a positive
	// _dropCount, and it should be negative.
	if (_dropRatio.filtered() < 0.6f) {
	_dropCount = -_dropCount;
	} else {
	_dropCount = 0;
	}
	}
	if (_dropCount > limit) {
	if (_dropCount == 0) {
	// Drop frames when we reset _dropCount.
	_dropCount--;
	return true;
	} else {
	// Keep frames as long as we haven't reached limit.
	_dropCount--;
	return false;
	}
	} else {
	_dropCount = 0;
	return false;
	}
	}
	_dropCount = 0;
	return false;

	// A simpler version, unfiltered and quicker
	// bool dropNext = _dropNext;
	// _dropNext = false;
	// return dropNext;
	}

	void FrameDropper::SetRates(float bitRate, float incoming_frame_rate) {
	// Bit rate of -1 means infinite bandwidth.
	_accumulatorMax = bitRate * _windowSize; // bitRate * windowSize (in seconds)
	if (_targetBitRate > 0.0f && bitRate < _targetBitRate &&
	_accumulator > _accumulatorMax) {
	// Rescale the accumulator level if the accumulator max decreases
	_accumulator = bitRate / _targetBitRate * _accumulator;
	}
	_targetBitRate = bitRate;
	CapAccumulator();
	_incoming_frame_rate = incoming_frame_rate;
	}

	float FrameDropper::ActualFrameRate(uint32_t inputFrameRate) const {
	if (!_enabled) {
	return static_cast<float>(inputFrameRate);
	}
	return inputFrameRate * (1.0f - _dropRatio.filtered());
	}

	// Put a cap on the accumulator, i.e., don't let it grow beyond some level.
	// This is a temporary fix for screencasting where very large frames from
	// encoder will cause very slow response (too many frame drops).
	void FrameDropper::CapAccumulator() {
	float max_accumulator = _targetBitRate * _cap_buffer_size;
	if (_accumulator > max_accumulator) {
	_accumulator = max_accumulator;
	}
	}
	} // namespace webrtc