modules/video_coding/main/source/frame_dropper.cc - src/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 "frame_dropper.h"
 #include "internal_defines.h"
 #include "trace.h"

 namespace webrtc
 {

 VCMFrameDropper::VCMFrameDropper(WebRtc_Word32 vcmId)
 :
 _vcmId(vcmId),
 _keyFrameSizeAvgKbits(0.9f),
 _keyFrameRatio(0.99f),
 _dropRatio(0.9f, 0.96f)
 {
     Reset();
 }

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

 void
 VCMFrameDropper::Fill(WebRtc_UWord32 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.Value())
         {
             // Remove the average key frame size since we
             // compensate for key frames when adding delta
             // frames.
             frameSizeKbits -= _keyFrameSizeAvgKbits.Value();
         }
         else
         {
             // Shouldn't be negative, so zero is the lower bound.
             frameSizeKbits = 0;
         }
         if (_keyFrameRatio.Value() > 1e-5 && 1 / _keyFrameRatio.Value() < _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<WebRtc_Word32>(1 / _keyFrameRatio.Value() + 0.5);
         }
         else
         {
             // Compensate for the key frame the following frames
             _keyFrameCount = static_cast<WebRtc_Word32>(_keyFrameSpreadFrames + 0.5);
         }
     }
     else
     {
         // Decrease the keyFrameRatio
         _keyFrameRatio.Apply(1.0, 0.0);
     }
     // Change the level of the accumulator (bucket)
     _accumulator += frameSizeKbits;
     CapAccumulator();
 }

 void
 VCMFrameDropper::Leak(WebRtc_UWord32 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.Value() > 0 && 1 / _keyFrameRatio.Value() < _keyFrameSpreadFrames)
         {
             T -= _keyFrameSizeAvgKbits.Value() * _keyFrameRatio.Value();
         }
         else
         {
             T -= _keyFrameSizeAvgKbits.Value() / _keyFrameSpreadFrames;
         }
         _keyFrameCount--;
     }
     _accumulator -= T;
     UpdateRatio();
 }

 void
 VCMFrameDropper::UpdateNack(WebRtc_UWord32 nackBytes)
 {
     if (!_enabled)
     {
         return;
     }
     _accumulator += static_cast<float>(nackBytes) * 8.0f / 1000.0f;
 }

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

 void
 VCMFrameDropper::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);
     }
     if (_accumulator < 0.0f)
     {
         _accumulator = 0.0f;
     }
     _wasBelowMax = _accumulator < _accumulatorMax;
     WEBRTC_TRACE(webrtc::kTraceDebug, webrtc::kTraceVideoCoding, VCMId(_vcmId),  "FrameDropper: dropRatio = %f accumulator = %f, accumulatorMax = %f", _dropRatio.Value(), _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
 VCMFrameDropper::DropFrame()
 {
     if (!_enabled)
     {
         return false;
     }
     if (_dropNext)
     {
         _dropNext = false;
         _dropCount = 0;
     }

     if (_dropRatio.Value() >= 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.Value();
         if (denom < 1e-5)
         {
             denom = (float)1e-5;
         }
         WebRtc_Word32 limit = static_cast<WebRtc_Word32>(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.Value() > 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.Value() > 0.0f && _dropRatio.Value() < 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.Value();
         if (denom < 1e-5)
         {
             denom = (float)1e-5;
         }
         WebRtc_Word32 limit = -static_cast<WebRtc_Word32>(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.Value() < 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
 VCMFrameDropper::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
 VCMFrameDropper::ActualFrameRate(WebRtc_UWord32 inputFrameRate) const
 {
     if (!_enabled)
     {
         return static_cast<float>(inputFrameRate);
     }
     return inputFrameRate * (1.0f - _dropRatio.Value());
 }

 // 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 VCMFrameDropper::CapAccumulator() {
   float max_accumulator = _targetBitRate * _cap_buffer_size;
   if (_accumulator > max_accumulator) {
     _accumulator = max_accumulator;
   }
 }

 }
	/*
	* 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 "frame_dropper.h"
	#include "internal_defines.h"
	#include "trace.h"

	namespace webrtc
	{

	VCMFrameDropper::VCMFrameDropper(WebRtc_Word32 vcmId)
	:
	_vcmId(vcmId),
	_keyFrameSizeAvgKbits(0.9f),
	_keyFrameRatio(0.99f),
	_dropRatio(0.9f, 0.96f)
	{
	Reset();
	}

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

	void
	VCMFrameDropper::Fill(WebRtc_UWord32 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.Value())
	{
	// Remove the average key frame size since we
	// compensate for key frames when adding delta
	// frames.
	frameSizeKbits -= _keyFrameSizeAvgKbits.Value();
	}
	else
	{
	// Shouldn't be negative, so zero is the lower bound.
	frameSizeKbits = 0;
	}
	if (_keyFrameRatio.Value() > 1e-5 && 1 / _keyFrameRatio.Value() < _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<WebRtc_Word32>(1 / _keyFrameRatio.Value() + 0.5);
	}
	else
	{
	// Compensate for the key frame the following frames
	_keyFrameCount = static_cast<WebRtc_Word32>(_keyFrameSpreadFrames + 0.5);
	}
	}
	else
	{
	// Decrease the keyFrameRatio
	_keyFrameRatio.Apply(1.0, 0.0);
	}
	// Change the level of the accumulator (bucket)
	_accumulator += frameSizeKbits;
	CapAccumulator();
	}

	void
	VCMFrameDropper::Leak(WebRtc_UWord32 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.Value() > 0 && 1 / _keyFrameRatio.Value() < _keyFrameSpreadFrames)
	{
	T -= _keyFrameSizeAvgKbits.Value() * _keyFrameRatio.Value();
	}
	else
	{
	T -= _keyFrameSizeAvgKbits.Value() / _keyFrameSpreadFrames;
	}
	_keyFrameCount--;
	}
	_accumulator -= T;
	UpdateRatio();
	}

	void
	VCMFrameDropper::UpdateNack(WebRtc_UWord32 nackBytes)
	{
	if (!_enabled)
	{
	return;
	}
	_accumulator += static_cast<float>(nackBytes) * 8.0f / 1000.0f;
	}

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

	void
	VCMFrameDropper::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);
	}
	if (_accumulator < 0.0f)
	{
	_accumulator = 0.0f;
	}
	_wasBelowMax = _accumulator < _accumulatorMax;
	WEBRTC_TRACE(webrtc::kTraceDebug, webrtc::kTraceVideoCoding, VCMId(_vcmId), "FrameDropper: dropRatio = %f accumulator = %f, accumulatorMax = %f", _dropRatio.Value(), _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
	VCMFrameDropper::DropFrame()
	{
	if (!_enabled)
	{
	return false;
	}
	if (_dropNext)
	{
	_dropNext = false;
	_dropCount = 0;
	}

	if (_dropRatio.Value() >= 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.Value();
	if (denom < 1e-5)
	{
	denom = (float)1e-5;
	}
	WebRtc_Word32 limit = static_cast<WebRtc_Word32>(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.Value() > 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.Value() > 0.0f && _dropRatio.Value() < 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.Value();
	if (denom < 1e-5)
	{
	denom = (float)1e-5;
	}
	WebRtc_Word32 limit = -static_cast<WebRtc_Word32>(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.Value() < 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
	VCMFrameDropper::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
	VCMFrameDropper::ActualFrameRate(WebRtc_UWord32 inputFrameRate) const
	{
	if (!_enabled)
	{
	return static_cast<float>(inputFrameRate);
	}
	return inputFrameRate * (1.0f - _dropRatio.Value());
	}

	// 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 VCMFrameDropper::CapAccumulator() {
	float max_accumulator = _targetBitRate * _cap_buffer_size;
	if (_accumulator > max_accumulator) {
	_accumulator = max_accumulator;
	}
	}

	}