针对强教师模型的伪标签选择难题,提出自适应筛选机制。
CW-BASS v2: Saturation-Aware Pseudo-Label Selection for Semi-Supervised Segmentation under Foundation-Model Teachers

- 根据教师置信度分布动态调整筛选策略,避免过拟合
- 在Pascal VOC和Cityscapes上达到接近UniMatch V2的性能
- 适用于基于DINOv2等强教师模型的半监督分割任务
半监督语义分割长期面临伪标签可信度判断问题。传统方法依赖动态阈值、类别课程等规则,适用于早期噪声大、置信度低的ResNet教师模型。但自监督基础编码器(如DINOv2)使置信度趋于饱和,原有过滤机制反而损害性能。本文提出CW-BASS v2,一种感知置信度饱和状态的伪标签选择方法:结合保留集校准与自适应置信下限,在一阶段中判断教师置信集可靠性(pi_kept = Pr[correct | c >= tau]),当可靠性达标(pi_kept >= tau)时严格筛选,否则启用自适应下限。该方法在六种DINOv2教师下无需调参即可正确决策。在饱和数据集上恢复了UniMatch V2性能(Pascal VOC 1/8: 87.4 vs 原始87.9;Cityscapes误差<0.5),在不可靠置信集场景(ADE20K, pi_kept ~89%)提升1.5 mIoU。其核心优势在于规避可测量的失效风险——当置信度范围压缩(98% Pascal像素≥0.95)时,固定阈值会过度保留噪声,导致自训练陷入确认偏见。
原文摘要 · Abstract (English)
Semi-supervised semantic segmentation has long turned on one question, which pseudo-labels to trust, and a generation of selection rules, dynamic thresholds, per-class curricula, soft confidence weights, answered it for the noisy, under-confident ResNet teachers of their day. Self-supervised foundation encoders change the regime: with a DINOv2 teacher, confidence saturates, so the filtering that helped a weak teacher can hurt a strong one. We propose CW-BASS v2, a saturation-aware pseudo-label selection method that reads the teacher's confidence regime rather than committing to one rule. It pairs held-out calibration, an unbiased per-class noise estimate, with a self-adaptive confidence floor that provably bounds retention away from 1, and combines them in a one-pass gate: measure the reliability of the teacher's confident set, pi_kept = Pr[correct | c >= tau], on a held-out slice, and filter strictly when it meets the confidence demanded (pi_kept >= tau), falling back to the adaptive floor otherwise. The boundary is the pre-existing operating threshold, not a value tuned to mIoU, and across six DINOv2 teachers it makes the correct strict-vs-floor call blind. CW-BASS v2 thus recovers the UniMatch V2 operating point on the saturated benchmarks by selecting strict (Pascal VOC 1/8 87.4 against its reported 87.9; Cityscapes within 0.5), and improves on it where the confident set is unreliable (pi_kept ~ 89%, ADE20K), where the floor edges ahead (+1.5 mIoU, single seed). The gate is principled because the failure it avoids is measured, not assumed: on a reliable, saturated teacher the confidence distribution's dynamic range collapses (98% of Pascal pixels >= 0.95), so an adaptive cutoff floods the retention mask and self-training decays into confirmation bias.
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