The Just Noticeable Difference (JND) is defined as the maximum change in a visual stimulus (image or video) which the Human Visual System (HVS) can tolerate without perceiving visual distortion. Previous JND research has largely focused on spatial distortions, yielding several datasets and models that predict spatial thresholds based on parameters such as Quantization Parameter (QP) or Quality Factor (QF). However, temporal thresholds, specifically the maximum frame rate reductions which viewers cannot detect, remain largely unexplored, despite their critical importance for efficient video coding. To address this gap, we introduce JNTD-DS, which, to the best of our knowledge, is the first benchmark dataset specifically designed to measure the Just Noticeable frame rate-based Temporal Difference (JNTD). The dataset comprises 50 video scenes covering various content, and the JNTD level associated with them. T e video scenes are studied through extensive subjective tests, comparing the high frame rate videos with their temporally downsampled versions. This forms 1196 opinion scores from 78 subjects. Analyzing the collected data confirms that JNTD thresholds, which are fundamentally defined by the HVS, are inherently complex and vary across content. By providing critical insights into HVS sensitivity to frame rate changes, the dataset enables content-adaptive frame rate optimization for perceptual video coding, allowing more efficient compression in video streaming and bandwidth-limited applications without compromising visual quality. We further demonstrate the practical impact of these insights by developing a JNTD prediction model and integrating it into a video compression pipeline, achieving an average bitrate reduction of 13.62% with only a marginal quality loss. The JNTD-DS is publicly available at https://github.com/sanaznami/JNTD-DS.

Just Noticeable Difference (JND) refers to the maximum level of distortion in an image or video sequence that remains imperceptible to the Human Visual System (HVS). Current JND-based studies predominantly rely on existing datasets, developing models predicting JND levels in terms of Quantization Parameter (QP) or Quality Factor (QF). However, these solutions primarily focus on spatial-based Perceptual Video Coding (PVC) and neglect temporal-based optimization, which highly affects the video bitrate. This paper addresses this limitation by introducing Just Noticeable frame rate-based Temporal Difference (JNTD) to determine the optimal Frame Rate (FR) based on human perception. A novel dataset comprising 50 high frame rate video sequences is collected through subjective assessments. Subsequently, an ensemble method is proposed to predict the JNTD, by leveraging deep and hand-crafted features, for robust prediction. Experimental evaluations include the integration of the proposed method into several codecs (H.264, H.265, H.266, and a new learned codec), showcasing its ability to reduce bitrate without compromising visual quality.

Emerging Learned image Compression (LC) achieves significant improvements in coding efficiency by end-to-end training of neural networks for compression. An important benefit of this approach over traditional codecs is that any optimization criteria can be directly applied to the encoder-decoder networks during training. Perceptual optimization of LC to comply with the Human Visual System (HVS) is among such criteria, which has not been fully explored yet. This paper addresses this gap by proposing a novel framework to integrate Just Noticeable Distortion (JND) principles into LC. Leveraging existing JND datasets, three perceptual optimization methods are proposed to integrate JND into the LC training process: (1) Pixel-Wise JND Loss (PWL) prioritizes pixel-by-pixel fidelity in reproducing JND characteristics, (2) Image-Wise JND Loss (IWL) emphasizes on overall imperceptible degradation levels, and (3) Feature-Wise JND Loss (FWL) aligns the reconstructed image features with perceptually significant features. Experimental evaluations demonstrate the effectiveness of JND integration, highlighting improvements in rate-distortion performance and visual quality, compared to baseline methods. The proposed methods add no extra complexity after training.

The Just Noticeable Difference (JND) refers to the smallest distortion in an image or video that can be perceived by Human Visual System (HVS), and is widely used in optimizing image/video compression. However, accurate JND modeling is very challenging due to its content dependence, and the complex nature of the HVS. Recent solutions train deep learning based JND prediction models, mainly based on a Quantization Parameter (QP) value, representing a single JND level, and train separate models to predict each JND level. We point out that a single QP-distance is insufficient to properly train a network with millions of parameters, for a complex content-dependent task. Inspired by recent advances in learned compression and multitask learning, we propose to address this problem by (1) learning to reconstruct the JND-quality frames, jointly with the QP prediction, and (2) jointly learning several JND levels to augment the learning performance. We propose a novel solution where first, an effective feature backbone is trained by learning to reconstruct JND-quality frames from the raw frames. Second, JND prediction models are trained based on features extracted from latent space (i.e., compressed domain), or reconstructed JND-quality frames. Third, a multi-JND model is designed, which jointly learns three JND levels, further reducing the prediction error. Extensive experimental results demonstrate that our multi-JND method outperforms the state-of-the-art and achieves an average JND1prediction error of only 1.57 in QP, and 0.72 dB in PSNR. Moreover, the multitask learning approach, and compressed domain prediction facilitate light-weight inference by significantly reducing the complexity and the number of parameters.

The limitation of the Human Visual System (HVS) in perceiving small distortions allows us to lower the bitrate required to achieve a certain visual quality. Predicting and applying the Just Noticeable Distortion (JND), which is a threshold for maximum unperceived level of distortions, is among the popular ways to do so. Recently, machine learning based methods have been able to reduce bitrate even further by improving JND prediction accuracy. However, accurate modeling of JND is very challenging, as it is highly content dependent. Furthermore, existing datasets provide little information to learn the best parameters. To remedy this issue, we propose a multi-task deep learning framework that jointly learns various complementary visual information. We design three separate methods and training strategies that jointly learn: (1) three JND levels, (2) visual attention map and a JND level, and (3) three JND levels and the visual attention map. We show that accumulating information from multiple tasks leads to a more robust prediction of JND. Experimental results confirm the superiority of our framework compared to the state-of-the-art.

Just Noticeable Distortion (JND) finds the minimum distortion level perceivable by humans. This can be a natural solution for setting the compression for each video region in perceptual video coding. However, existing JND-based solutions estimate JND levels for each video frame and ignore the fact that different video regions have different perceptual importance. To address this issue, we propose a Block-Level Just Noticeable Distortion-based Perceptual (BL-JUNIPER) framework for video coding. The proposed four-stage framework combines different perceptual information to further improve the prediction accuracy. The JND mapping in the first stage derives block-level JNDs from frame-level information without the need to collect a new bock-level JND dataset. In the second stage, an efficient CNN-based model is proposed to predict JND levels for each block according to spatial and temporal characteristics. Unlike existing methods, BL-JUNIPER works on raw video frames and avoids re-encoding each frame several times, making it computationally practical. Third, the visual importance of each block is measured using a visual attention model. Finally, a proposed quantization control algorithm uses both JND levels and visual importance to adjust the Quantization Parameter (QP) for each block. The specific algorithm for each stage of the proposed framework can be changed, as long as the input and output formats of each block are followed, without the need to change other stages, based on any current or future methods, providing a flexible and robust solution. Extensive experimental results demonstrate that BL-JUNIPER achieves a mean bitrate reduction of 27.75% with a Delta Mean Opinion Score (DMOS) close to zero and BD-Rate gains of 25.44% based on MOS, compared to the baseline encoding, and also gains a better performance compared to competing methods.