Evaluating perceived video quality is essential for ensuring high Quality of Experience (QoE) in modern streaming applications. While existing subjective datasets and Video Quality Metrics (VQMs) cover a broad quality range, many practical use cases especially for premium users focus on high quality scenarios requiring finer granularity. Just Noticeable Difference (JND) has emerged as a key concept for modeling perceptual thresholds in these high end regions and plays an important role in perceptual bitrate ladder construction. However, the relationship between JND and the more widely used Mean Opinion Score (MOS) remains unclear. In this paper, we conduct a Degradation Category Rating (DCR) subjective study based on an existing JND dataset to examine how MOS corresponds to the 75% Satisfied User Ratio (SUR) points of the 1st and 2nd JNDs. We find that while MOS values at JND points generally align with theoretical expectations (e.g., 4.75 for the 75% SUR of the 1st JND), the reverse mapping from MOS to JND is ambiguous due to overlapping confidence intervals across PVS indices. Statistical significance analysis further shows that DCR studies with limited participants may not detect meaningful differences between reference and JND videos.

翻译：评估感知视频质量对于确保现代流媒体应用中的高质量体验至关重要。尽管现有的主观数据集和视频质量指标涵盖了广泛的质量范围，但许多实际用例（尤其是针对高端用户）聚焦于需要更精细粒度的高质量场景。恰可察觉差异已成为在这些高端区域建模感知阈值的关键概念，并在感知码率阶梯构建中发挥重要作用。然而，JND与更广泛使用的平均意见分数之间的关系尚不明确。本文基于现有JND数据集开展了一项退化类别评分主观研究，以考察MOS如何对应于第一和第二JND的75%满意用户比例点。我们发现，尽管JND点处的MOS值总体上符合理论预期（例如，第一JND的75% SUR对应4.75分），但由于不同处理视频序列指数间存在重叠的置信区间，从MOS到JND的反向映射具有模糊性。统计显著性分析进一步表明，参与者数量有限的DCR研究可能无法检测参考视频与JND视频之间的显著差异。