Methods for Improving the Tone Mapping for Backward Compatible High Dynamic Range Image and Video Coding

International audienceBackward compatibility for high dynamic range image and video compression forms one of the essential requirements in the transition phase from low dynamic range (LDR) displays to high dynamic range (HDR) displays. In a recent work [1], the problems of tone mapping and HDR video coding are originally fused together in the same mathematical framework, and an optimized solution for tone mapping is achieved in terms of the mean square error (MSE) of the logarithm of luminance values. In this paper, we improve this pioneer study in three aspects by considering its three shortcomings. First, the proposed method [1] works over the logarithms of luminance values which are not uniform with respect to Human Visual System (HVS) sensitivity. We propose to use the perceptually uniform luminance values as an alternative for the optimization of tone mapping curve. Second, the proposed method [1] does not take the quality of the resulting tone mapped images into account during the formulation in contrary to the main goal of tone mapping research. We include the LDR image quality as a constraint to the optimization problem and develop a generic methodology to compromise the trade-off between HDR and LDR image qualities for coding. Third, the proposed method [1] simply applies a low-pass filter to the generated tone curves for video frames to avoid flickering during the adaptation of the method to the video. We instead include an HVS based flickering constraint to the optimization and derive a methodology to compromise the trade-off between the rate-distortion performance and flickering distortion. The superiority of the proposed methodologies is verified with experiments on HDR images and video sequences

Encoder and Decoder Side Global and Local Motion Estimation for Distributed Video Coding

International audienceIn this paper, we propose a new Distributed Video Coding (DVC) architecture where motion estimation is performed both at the encoder and decoder, effectively combining global and local motion models. We show that the proposed approach improves significantly the quality of Side Information (SI), especially for sequences with complex motion patterns. In turn, it leads to rate-distortion gains of up to 1 dB when compared to the state-of-the-art DISCOVER DVC codec

A comparative survey on high dynamic range video compression

International audienceHigh dynamic range (HDR) video compression has until now been approached by using the high profile of existing state-of-the-art H.264/AVC (Advanced Video Coding) codec or by separately encoding low dynamic range (LDR) video and the residue resulted from the estimation of HDR video from LDR video. Although the latter approach has a distinctive advantage of providing backward compatibility to 8-bit LDR displays, the superiority of one approach to the other in terms of the rate distortion trade-off has not been verified yet. In this paper, we first give a detailed overview of the methods in these two approaches. Then, we experimentally compare two approaches with respect to different objective and perceptual metrics, such as HDR mean square error (HDR MSE), perceptually uniform peak signal to noise ratio (PU PSNR) and HDR visible difference predictor (HDR VDP). We first conclude that the optimized methods for backward compatibility to 8-bit LDR displays are superior to the method designed for high profile encoder both for 8-bit and 12-bit mappings in terms of all metrics. Second, using higher bit-depths with a high profile encoder is giving better rate-distortion performances than employing an 8-bit mapping with an 8-bit encoder for the same method, in particular when the dynamic range of the video sequence is high. Third, rather than encoding of the residue signal in backward compatible methods, changing the quantization step size of the LDR layer encoder would be sufficient to achieve a required quality. In other words, the quality of tone mapping is more important than residue encoding for the performance of HDR image and video coding

PCQA-GRAPHPOINT: Efficients Deep-Based Graph Metric For Point Cloud Quality Assessment

Following the advent of immersive technologies and the increasing interest in representing interactive geometrical format, 3D Point Clouds (PC) have emerged as a promising solution and effective means to display 3D visual information. In addition to other challenges in immersive applications, objective and subjective quality assessments of compressed 3D content remain open problems and an area of research interest. Yet most of the efforts in the research area ignore the local geometrical structures between points representation. In this paper, we overcome this limitation by introducing a novel and efficient objective metric for Point Clouds Quality Assessment, by learning local intrinsic dependencies using Graph Neural Network (GNN). To evaluate the performance of our method, two well-known datasets have been used. The results demonstrate the effectiveness and reliability of our solution compared to state-of-the-art metrics

H.264/AVC Video Scrambling for Privacy Protection

In this paper, we address the problem of privacy in video surveillance systems. More specifically, we consider the case of H.264/AVC which is the state-of-the-art in video coding. We assume that Regions of Interest (ROI), containing privacy-sensitive information, have been identified. The content of these regions are then concealed using scrambling. More specifically, we introduce two region-based scrambling techniques. The first one pseudo- randomly flips the sign of transform coefficients during encoding. The second one is performing a pseudo-random permutation of transform coefficients in a block. The Flexible Macroblock Ordering (FMO) mechanism of H.264/AVC is exploited to discriminate between the ROI which are scrambled and the background which remains clear. Experimental results show that both techniques are able to effectively hide private information in ROI, while the scene remains comprehensible. Furthermore, the loss in coding efficiency stays small, whereas the required additional computational complexity is negligible

Scrambling for Privacy Protection in Video Surveillance Systems

In this paper, we address the problem of privacy protection in video surveillance. We introduce two efficient approaches to conceal Regions of Interest (ROI) based on transform-domain or codestream-domain scrambling. In the first technique, the sign of selected transform coefficients is pseudo-randomly flipped during encoding. In the second method, some bits of the codestream are pseudo-randomly inverted. We address more specifically the cases of MPEG-4 as it is today the prevailing standard in video surveillance equipment. Simulations show that both techniques successfully hide private data in ROI while the scene remains comprehensible. Additionally, the amount of noise introduced by the scrambling process can be adjusted. Finally, the impact on coding efficiency performance is small and the required computational complexity is negligible

The JPEG XR Image Coding Standard

JPEG XR is the newest image coding standard from the JPEG committee. It primarily targets the representation of continuous-tone still images such as photographic images, and achieves high image quality, on par with JPEG 2000, while requiring low computational resources and storage capacity. Moreover, it effectively addresses the needs of emerging high dynamic range imagery applications by including support for a wide range of image representation format

On Comparing JPEG 2000 and Intraframe AVC

In this work, a performance evaluation of AVC Intra and JPEG2000 in terms of rate-distortion performance is conducted. A rich set of test sequences with different spatial resolutions is used in this evaluation. Furthermore, the comparison is made with both the Main and High profiles of AVC Intra. For high spatial resolution sequences, our results show that JPEG2000 is very competitive with AVC High Profile Intra and outperforms the Main Profile. For Intermediate and low spatial resolution sequences JPEG2000 is outperformed by both Profiles of AVC Intra