Referring Multi-Object Tracking has attracted increasing attention due to its human-friendly interactive characteristics, yet it exhibits limitations in low-visibility conditions, such as nighttime, smoke, and other challenging scenarios. To overcome this limitation, we propose a new RGB-Thermal RMOT task, named RT-RMOT, which aims to fuse RGB appearance features with the illumination robustness of the thermal modality to enable all-day referring multi-object tracking. To promote research on RT-RMOT, we construct the first Referring Multi-Object Tracking dataset under RGB-Thermal modality, named RefRT. It contains 388 language descriptions, 1,250 tracked targets, and 166,147 Language-RGB-Thermal (L-RGB-T) triplets. Furthermore, we propose RTrack, a framework built upon a multimodal large language model (MLLM) that integrates RGB, thermal, and textual features. Since the initial framework still leaves room for improvement, we introduce a Group Sequence Policy Optimization (GSPO) strategy to further exploit the model's potential. To alleviate training instability during RL fine-tuning, we introduce a Clipped Advantage Scaling (CAS) strategy to suppress gradient explosion. In addition, we design Structured Output Reward and Comprehensive Detection Reward to balance exploration and exploitation, thereby improving the completeness and accuracy of target perception. Extensive experiments on the RefRT dataset demonstrate the effectiveness of the proposed RTrack framework.
Figures & tables
Figure 1: The difference between RMOT and RT-RMOT. RMOT model takes RGB images as input, but pedestrian positions cannot be reliably obtained from RGB alone, often leading to tracking failure. RT-RMOT model leverages thermal (T) images to obtain pedestrian contours and locations, and combines them with crosswalk regions provided by RGB images, enabling precise identification and tracking of people described by language.
Figure 2: Data annotation process. The annotation process consists of three steps: (1) Target Pre-selection and Annotation; (2) GPT-Assisted Generation of Attribute Descriptions; (3) Human Verification and Refinement. First, visually similar targets are selected, and bounding boxes are annotated across the entire sequence. Then, annotated key frames and task instructions are provided to GPT to analyze the target’s category, scene, appearance, motion, and spatial position. Finally, GPT-generated attributes are integrated into initial descriptions, which is refined through multiple annotators’ review to produce the final language descriptions.
Figure 3: Visualization results on the RefRT dataset. (a) The word cloud of the RefRT dataset contains a rich set of keywords. (b) The RefRT dataset covers diverse scenes, targets and attributes. (c) After normalizing the three-dimensional data of the language descriptions in the RefRT dataset, the broad distribution characteristics of the dataset are revealed.
Figure 4: Overall pipeline of RTrack. The RTrack framework consists of three modules: (1) Large-model perception module: performs inference detection of the target in the current frame based on the language description. (2) Trajectory Prediction Module: predicts the target box in the current frame based on the historical trajectory. (3) Identity Association Module: matches the trajectory box and the detection box to generate the target ID. Among them, the GSPO algorithm includes three aspects: (a) CAS strategy: constrains relative rewards to avoid gradient explosion. (b) Structured output reward: requires the model to format the output and limits the output length. (c) Comprehensive detection reward: completes the output encouragement and accurate output based on the IoU value.
Modality
Method
Venue
HOTA↑
DetA↑
AssA↑
DetRe↑
DetPr↑
AssRe↑
AssPr↑
LocA↑
RGB
TransRMOT [ 20 ]
CVPR 2023
8.69
2.57
29.96
3.01
14.46
30.73
85.49
79.63
TempRMOT [ 26 ]
ArXiv 2024
8.19
1.86
36.23
2.04
16.68
39.28
75.39
77.48
CRTracker [ 3 ]
AAAI2025
9.30
2.37
37.01
3.81
5.83
40.10
67.48
73.25
YOLOX+ByteTrack+ iKUN [ 5 ]
CVPR 2024
2.32
0.29
19.86
0.29
12.71
21.18
61.45
69.70
Qwen2.5-VL-3B [ 2 ]
ArXiv 2025
2.09
0.93
5.28
0.97
17.14
5.40
87.46
76.69
RGBT
DeformCAT [ 7 ] +SORT+iKUN
IEEE TMM
2.03
0.41
11.25
0.77
0.87
12.07
47.65
62.61
Table 1: Performance of many methods on the RefRT test set. ↑ indicates that higher scores are better. The best results are marked in bold .
Modality
Method
Size
RL Fine-tuning
HOTA↑
DetA↑
AssA↑
DetRe↑
DetPr↑
AssRe↑
AssPr↑
LocA↑
RGB
Qwen2.5-VL [ 2 ]
3B
✗
2.09
0.93
5.28
0.97
17.14
5.40
87.46
76.69
RTrack
3B
✓
12.49
11.05
15.25
16.14
23.95
16.18
79.39
73.90
RGBT
Qwen2.5-VL [ 2 ]
3B
✗
4.98
2.59
10.19
3.05
14.29
10.65
83.40
75.52
RTrack
3B
✓
15.53
12.39
20.79
20.15
22.78
22.02
81.99
75.53
Table 2: Results of more experiments on the RefRT test set.↑ indicates that higher scores are better. The best results are marked in bold .
Module
Method
Size
RL Fine-tuning
HOTA↑
DetA↑
AssA↑
DetRe↑
DetPr↑
AssRe↑
AssPr↑
LocA↑
A. MLLMs
LLaVA [ 13 ]
7B
✗
1.13
0.29
5.32
8.84
0.28
7.32
19.47
57.69
LLaVA-NeXT [ 12 ]
8B
✗
2.99
0.84
13.35
5.70
0.96
17.84
38.32
60.17
InternVL2 [ 4 ]
8B
✗
0.82
0.18
4.77
10.77
0.18
5.71
31.96
60.10
Qwen2.5-VL [ 2 ]
3B
✗
4.98
2.59
10.19
3.05
14.29
10.65
83.40
75.52
B. Training Strategy
w/o CAS
3B
✓
5.27
3.93
7.37
4.32
28.11
7.43
90.32
78.63
w/o Struct. Reward
3B
✓
11.24
9.47
14.25
16.81
17.10
14.79
86.08
77.20
Table 3: Ablation study results of RTrack on the RefRT test set. Module A represent the untrained results, while Module B reflects the results after training. ↑ indicates higher is better. Best results are in bold .
Figure 5: Qualitative zero-shot results of RTrack on the test set of RT-RMOT task.
Dataset
Source
Videos
Scene
Desc.
Instance
Instance/Desc.
Bbox
Multi-Object
RGBT
Real-world
RGBT234
IJCV2019
234
Urban, campus
234
–
–
234
×
✓
✓
GTOT
CVPR2016
50
Urban, campus
–
–
–
15.8k
×
✓
✓
RGBT-Tiny
arXiv 2024
115
Port, urban roads
–
–
–
1.2M
×
✓
✓
Refer-KITTI
CVPR2023
18
Urban, road mixed
818
8.7k
10.7
0.36M
✓
×
✓
Refer-KITTI-V2
arXiv 2024
21
Urban, highways, etc.
9.8k
65.4k
607
3.06M
✓
×
✓
Refer-Dance
CVPR2024
65
Mainly indoor
1.9k
650
0.34
0.55M
✓
×
✓
Table 4: Comparison with Existing Datasets. The Desc. indicates the number of language descriptions, and Instance/Desc. represents the average number of target instances per description. Check marks indicate whether a dataset supports Multi-Object Tracking, includes RGBT modalities data, and contains real-world scenarios. The comparison results indicate that the RefRT dataset fulfills the combined requirements of RGBT modalities inputs, diverse object categories, and comprehensive semantic annotations.
Prompt Design
HOTA↑
DetA↑
AssA↑
DetRe↑
DetPr↑
AssRe↑
AssPr↑
LocA↑
Short Prompt
13.92
11.99
17.42
17.92
24.75
18.30
82.87
75.64
Description-First Prompt
13.00
11.10
16.25
20.21
18.75
17.05
81.68
75.65
No Coordinate Example Prompt
16.29
12.26
22.90
17.95
25.85
24.49
81.25
75.35
Base Prompt (Ours)
15.53
12.39
20.79
20.15
22.78
22.02
81.99
75.53
Table 5: Ablation study on different prompt designs in RTrack.
Batch Size
Epochs
Learning Rate
LoRA- r
LoRA- α
LoRA Dropout
Generation Num
Max Len
Beta
Epsilon
Scalemax
Lmin
Lmax
Llow
Lhigh
α
β
γ
λ
1
1
1×10−5
8
16
0.05
4
512
0.001
1×10−3
3.0
80
600
140
200
0.5
1
0.5
2
Table 6: Hyperparameter configuration used in the RL fine-tuning process.
Figure 6: More qualitative results of our RTrack framework on the test set of the RefRT dataset . It is worth noting that our framework can perform long-term tracking, rather than tracking only in the initial frame.
Figure 7: Ground-Truth Results in the RefRT dataset provide diverse, RGBT aligned real-world data.
College of Command and Control Engineering, Army Engineering University of PLA · School of Future Technology, Dalian University of Technology · School of Information and Communication Engineering, Dalian University of Technology