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streamtracker_frame.go
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/
streamtracker_frame.go
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// Copyright 2023 LiveKit, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package streamtracker
import (
"math"
"time"
"github.com/livekit/livekit-server/pkg/config"
"github.com/livekit/protocol/logger"
)
const (
checkInterval = 500 * time.Millisecond
statusCheckTolerance = 0.98
frameRateResolution = 0.01 // 1 frame every 100 seconds
frameRateIncreaseFactor = 0.6 // slow increase
frameRateDecreaseFactor = 0.9 // fast decrease
)
type StreamTrackerFrameParams struct {
Config config.StreamTrackerFrameConfig
ClockRate uint32
Logger logger.Logger
}
type StreamTrackerFrame struct {
params StreamTrackerFrameParams
initialized bool
tsInitialized bool
oldestTS uint32
newestTS uint32
numFrames int
estimatedFrameRate float64
evalInterval time.Duration
lastStatusCheckAt time.Time
}
func NewStreamTrackerFrame(params StreamTrackerFrameParams) StreamTrackerImpl {
s := &StreamTrackerFrame{
params: params,
}
s.Reset()
return s
}
func (s *StreamTrackerFrame) Start() {
}
func (s *StreamTrackerFrame) Stop() {
}
func (s *StreamTrackerFrame) Reset() {
s.initialized = false
s.resetFPSCalculator()
s.lastStatusCheckAt = time.Time{}
}
func (s *StreamTrackerFrame) resetFPSCalculator() {
s.tsInitialized = false
s.oldestTS = 0
s.newestTS = 0
s.numFrames = 0
s.estimatedFrameRate = 0.0
s.updateEvalInterval()
}
func (s *StreamTrackerFrame) GetCheckInterval() time.Duration {
return checkInterval
}
func (s *StreamTrackerFrame) Observe(hasMarker bool, ts uint32) StreamStatusChange {
if hasMarker {
if !s.tsInitialized {
s.tsInitialized = true
s.oldestTS = ts
s.newestTS = ts
s.numFrames = 1
} else {
diff := ts - s.oldestTS
if diff > (1 << 31) {
s.oldestTS = ts
}
diff = ts - s.newestTS
if diff < (1 << 31) {
s.newestTS = ts
}
s.numFrames++
}
}
// When starting up, check for first packet and declare active.
// Happens under following conditions
// 1. Start up
// 2. Unmute (stream restarting)
// 3. Layer starting after dynacast pause
if !s.initialized {
s.initialized = true
s.lastStatusCheckAt = time.Now()
return StreamStatusChangeActive
}
return StreamStatusChangeNone
}
func (s *StreamTrackerFrame) CheckStatus() StreamStatusChange {
if !s.initialized {
// should not be getting called when not initialized, but be safe
return StreamStatusChangeNone
}
if !s.updateStatusCheckTime() {
return StreamStatusChangeNone
}
if s.updateEstimatedFrameRate() == 0.0 {
// when stream is stopped, reset FPS calculator to ensure re-start is not done until at least two frames are available,
// i. e. enough frames available to be able to calculate FPS
s.resetFPSCalculator()
return StreamStatusChangeStopped
}
return StreamStatusChangeActive
}
func (s *StreamTrackerFrame) updateStatusCheckTime() bool {
// check only at intervals based on estimated frame rate
if s.lastStatusCheckAt.IsZero() {
s.lastStatusCheckAt = time.Now()
}
if time.Since(s.lastStatusCheckAt) < time.Duration(statusCheckTolerance*float64(s.evalInterval)) {
return false
}
s.lastStatusCheckAt = time.Now()
return true
}
func (s *StreamTrackerFrame) updateEstimatedFrameRate() float64 {
diff := s.newestTS - s.oldestTS
if diff == 0 || s.numFrames < 2 {
return 0.0
}
frameRate := roundFrameRate(float64(s.params.ClockRate) / float64(diff) * float64(s.numFrames-1))
// reset for next evaluation interval
s.oldestTS = s.newestTS
s.numFrames = 1
factor := 1.0
switch {
case s.estimatedFrameRate < frameRate:
// slow increase, prevents shortening eval interval too quickly on frame rate going up
factor = frameRateIncreaseFactor
case s.estimatedFrameRate > frameRate:
// fast decrease, prevents declaring stream stop too quickly on frame rate going down
factor = frameRateDecreaseFactor
}
estimatedFrameRate := roundFrameRate(frameRate*factor + s.estimatedFrameRate*(1.0-factor))
if s.estimatedFrameRate != estimatedFrameRate {
s.estimatedFrameRate = estimatedFrameRate
s.updateEvalInterval()
s.params.Logger.Debugw("updating estimated frame rate", "estimatedFPS", estimatedFrameRate, "evalInterval", s.evalInterval)
}
return frameRate
}
func (s *StreamTrackerFrame) updateEvalInterval() {
// STREAM-TRACKER-FRAME-TODO: This will run into challenges for frame rate falling steeply, How to address that?
// Maybe, look at some referential rules (between layers) for possibilities to solve it. Currently, this is addressed
// by setting a source aware min FPS to ensure evaluation window is long enough to avoid declaring stop too quickly.
s.evalInterval = checkInterval
if s.estimatedFrameRate > 0.0 {
estimatedFrameRateInterval := time.Duration(float64(time.Second) / s.estimatedFrameRate)
if estimatedFrameRateInterval > s.evalInterval {
s.evalInterval = estimatedFrameRateInterval
}
}
if s.params.Config.MinFPS > 0.0 {
minFPSInterval := time.Duration(float64(time.Second) / s.params.Config.MinFPS)
if minFPSInterval > s.evalInterval {
s.evalInterval = minFPSInterval
}
}
}
// ------------------------------------------------------------------------------
func roundFrameRate(frameRate float64) float64 {
return math.Round(frameRate/frameRateResolution) * frameRateResolution
}