bytetrack-counter-go/pkg/bytetrack/tracker.go

package bytetrack

import (
	"git.proit.id/dsutanto/bytetrack-counter-go/internal/iou"
	"git.proit.id/dsutanto/bytetrack-counter-go/pkg/kalman"
)

type ByteTracker struct {
	HighThresh  float64
	LowThresh   float64
	MatchThresh float64
	Buffer      int
	MinHits     int

	tracked []*kalman.Tracker
	lost    []*kalman.Tracker
	removed []*kalman.Tracker
	frameID int
}

func New(highThresh, lowThresh, matchThresh float64, buffer, minHits int) *ByteTracker {
	return &ByteTracker{
		HighThresh:  highThresh,
		LowThresh:   lowThresh,
		MatchThresh: matchThresh,
		Buffer:      buffer,
		MinHits:     minHits,
	}
}

type UpdateResult struct {
	Tracked    map[int]float64
	DetToTrack map[int]int
	Lost       map[int]float64
}

func (bt *ByteTracker) Update(boxes [][4]float64, scores []float64) UpdateResult {
	bt.frameID++

	result := UpdateResult{
		Tracked:    make(map[int]float64),
		DetToTrack: make(map[int]int),
		Lost:       make(map[int]float64),
	}

	n := len(boxes)

	var dets [][4]float64
	var filtToGlobal []int
	var highFiltIdx []int
	var lowFiltIdx []int

	for i := 0; i < n; i++ {
		if scores[i] > bt.LowThresh {
			filtToGlobal = append(filtToGlobal, i)
			dets = append(dets, boxes[i])
			if scores[i] > bt.HighThresh {
				highFiltIdx = append(highFiltIdx, len(dets)-1)
			} else {
				lowFiltIdx = append(lowFiltIdx, len(dets)-1)
			}
		}
	}

	pool := make([]*kalman.Tracker, 0, len(bt.tracked)+len(bt.lost))
	pool = append(pool, bt.tracked...)
	pool = append(pool, bt.lost...)

	numPool := len(pool)
	var poolBoxes [][4]float64
	if numPool > 0 {
		poolBoxes = make([][4]float64, numPool)
		for i, trk := range pool {
			trk.Predict()
			poolBoxes[i] = trk.GetState()
		}
	}

	matchedPool := make(map[int]bool)

	if numPool > 0 && len(highFiltIdx) > 0 {
		highDets := make([][4]float64, len(highFiltIdx))
		for i, hi := range highFiltIdx {
			highDets[i] = dets[hi]
		}
		iouMat := iou.PairwiseIoU(highDets, poolBoxes)
		cost := make([][]float64, len(iouMat))
		for i := range cost {
			cost[i] = make([]float64, len(iouMat[i]))
			for j := range cost[i] {
				cost[i][j] = 1.0 - iouMat[i][j]
			}
		}
		matches := iou.GreedyMatchRowCol(cost, 1.0-bt.MatchThresh)
		for _, m := range matches {
			filtIdx := highFiltIdx[m.Row]
			globalIdx := filtToGlobal[filtIdx]
			ti := m.Col
			pool[ti].Update(dets[filtIdx])
			if pool[ti].HitStreak < 1 {
				pool[ti].HitStreak = 1
			}
			matchedPool[ti] = true
			result.DetToTrack[globalIdx] = pool[ti].ID
			result.Tracked[pool[ti].ID] = pool[ti].GetCX()
		}
	}

	var unmatchedPool []int
	for i := 0; i < numPool; i++ {
		if !matchedPool[i] {
			unmatchedPool = append(unmatchedPool, i)
		}
	}

	if len(lowFiltIdx) > 0 && len(unmatchedPool) > 0 {
		lowDets := make([][4]float64, len(lowFiltIdx))
		for i, li := range lowFiltIdx {
			lowDets[i] = dets[li]
		}
		unmatchedBoxes := make([][4]float64, len(unmatchedPool))
		for i, pi := range unmatchedPool {
			unmatchedBoxes[i] = poolBoxes[pi]
		}
		iouMat2 := iou.PairwiseIoU(lowDets, unmatchedBoxes)
		cost2 := make([][]float64, len(iouMat2))
		for i := range cost2 {
			cost2[i] = make([]float64, len(iouMat2[i]))
			for j := range cost2[i] {
				cost2[i][j] = 1.0 - iouMat2[i][j]
			}
		}
		matches2 := iou.GreedyMatchRowCol(cost2, 0.5)
		for _, m := range matches2 {
			filtIdx := lowFiltIdx[m.Row]
			globalIdx := filtToGlobal[filtIdx]
			ti := unmatchedPool[m.Col]
			pool[ti].Update(dets[filtIdx])
			if pool[ti].HitStreak < 1 {
				pool[ti].HitStreak = 1
			}
			matchedPool[ti] = true
			result.DetToTrack[globalIdx] = pool[ti].ID
			result.Tracked[pool[ti].ID] = pool[ti].GetCX()
		}
	}

	for i, trk := range pool {
		if !matchedPool[i] {
			trk.HitStreak = 0
		}
	}

	newTracked := make([]*kalman.Tracker, 0)
	newLost := make([]*kalman.Tracker, 0)
	for _, trk := range pool {
		if trk.TimeSinceUpd > bt.Buffer {
			bt.removed = append(bt.removed, trk)
		} else if trk.TimeSinceUpd > 0 {
			newLost = append(newLost, trk)
		} else {
			newTracked = append(newTracked, trk)
		}
	}
	bt.tracked = newTracked
	bt.lost = newLost

	for _, trk := range bt.tracked {
		if trk.HitStreak >= bt.MinHits || trk.Hits >= bt.MinHits {
			result.Tracked[trk.ID] = trk.GetCX()
		}
	}
	for _, trk := range bt.lost {
		if trk.HitStreak >= bt.MinHits || trk.Hits >= bt.MinHits {
			result.Tracked[trk.ID] = trk.GetCX()
			result.Lost[trk.ID] = trk.GetCX()
		}
	}

	matchedDets := make(map[int]bool)
	for idx := range result.DetToTrack {
		matchedDets[idx] = true
	}
	for _, fi := range highFiltIdx {
		globalIdx := filtToGlobal[fi]
		if !matchedDets[globalIdx] {
			trk := kalman.NewTracker(dets[fi])
			bt.tracked = append(bt.tracked, trk)
			result.DetToTrack[globalIdx] = trk.ID
			result.Tracked[trk.ID] = trk.GetCX()
		}
	}

	return result
}