Visually lossless image coding in isochronous display streaming or plesiochronous networks reduces link complexity and power consumption and increases available link bandwidth. A new set of codecs developed within the last four years promise a new level of coding quality, but require new techniques that are sufficiently sensitive to the small artifacts or color variations induced by this new breed of codecs. This paper begins with a summary of the new ISO/IEC 29170-2, a procedure for evaluation of lossless coding and reports the new work by JPEG to extend the procedure in two important ways, for HDR content and for evaluating the differences between still images, panning images and image sequences. ISO/IEC 29170-2 relies on processing test images through a well-defined process chain for subjective, forced-choice psychophysical experiments. The procedure sets an acceptable quality level equal to one just noticeable difference. Traditional image and video coding evaluation techniques, such as, those used for television evaluation have not proven sufficiently sensitive to the small artifacts that may be induced by this breed of codecs. In 2015, JPEG received new requirements to expand evaluation of visually lossless coding for high dynamic range images, slowly moving images, i.e., panning, and image sequences. These requirements are the basis for new amendments of the ISO/IEC 29170-2 procedures described in this paper. These amendments promise to be highly useful for the new content in television and cinema mezzanine networks. The amendments passed the final ballot in April 2017 and are on track to be published in 2018.
In March 2016 the Joint Photographic Experts Group (JPEG), formally known as ISO/IEC SC29 WG1, issued
a call for proposals soliciting compression technologies for a low-latency, lightweight and visually transparent
video compression scheme. Within the JPEG family of standards, this scheme was denominated JPEG XS.
The subjective evaluation of visually lossless compressed video sequences at high resolutions and bit depths
poses particular challenges. This paper describes the adopted procedures, the subjective evaluation setup, the
evaluation process and summarizes the obtained results which were achieved in the context of the JPEG XS
Recently several papers reported efficient techniques to compress digital holograms. Typically, the rate-distortion performance of these solutions was evaluated by means of objective metrics such as Peak Signal-to-Noise Ratio (PSNR) or the Structural Similarity Index Measure (SSIM) by either evaluating the quality of the decoded hologram or the reconstructed compressed hologram. Seen the specific nature of holograms, it is relevant to question to what extend these metrics provide information on the effective visual quality of the reconstructed hologram. Given that today no holographic display technology is available that would allow for a proper subjective evaluation experiment, we propose in this paper a methodology that is based on assessing the quality of a reconstructed compressed hologram on a regular 2D display. In parallel, we also evaluate several coding engines, namely JPEG configured with the default perceptual quantization tables and with uniform quantization tables, JPEG 2000, JPEG 2000 extended with arbitrary packet decompositions and direction-adaptive filters and H.265/HEVC configured in intra-frame mode. The experimental results indicate that the perceived visual quality and the objective measures are well correlated. Moreover, also the superiority of the HEVC and the extended JPEG 2000 coding engines was confirmed, particularly at lower bitrates.
The JPEG standard has known an enormous market adoption. Daily, billions of pictures are created, stored and exchanged in this format. The JPEG committee acknowledges this success and spends continued efforts in maintaining and expanding the standard specifications. JPEG XT is a standardization effort targeting the extension of the JPEG features by enabling support for high dynamic range imaging, lossless and near-lossless coding, and alpha channel coding, while also guaranteeing backward and forward compatibility with the JPEG legacy format. This paper gives an overview of the current status of the JPEG XT standards suite. It discusses the JPEG legacy specification, and details how higher dynamic range support is facilitated both for integer and floating-point color representations. The paper shows how JPEG XT's support for lossless and near-lossless coding of low and high dynamic range images is achieved in combination with backward compatibility to JPEG legacy. In addition, the extensible boxed-based JPEG XT file format on which all following and future extensions of JPEG will be based is introduced. This paper also details how the lossy and lossless representations of alpha channels are supported to allow coding transparency information and arbitrarily shaped images. Finally, we conclude by giving prospects on upcoming JPEG standardization initiative JPEG Privacy & Security, and a number of other possible extensions in JPEG XT.
With the advent of modern computing and imaging technologies, digital holography is becoming widespread in various scientific disciplines such as microscopy, interferometry, surface shape measurements, vibration analysis, data encoding, and certification. Therefore, designing an efficient data representation technology is of particular importance. Off-axis holograms have very different signal properties with respect to regular imagery, because they represent a recorded interference pattern with its energy biased toward the high-frequency bands. This causes traditional images’ coders, which assume an underlying 1/f2 power spectral density distribution, to perform suboptimally for this type of imagery. We propose a JPEG 2000-based codec framework that provides a generic architecture suitable for the compression of many types of off-axis holograms. This framework has a JPEG 2000 codec at its core, extended with (1) fully arbitrary wavelet decomposition styles and (2) directional wavelet transforms. Using this codec, we report significant improvements in coding performance for off-axis holography relative to the conventional JPEG 2000 standard, with Bjøntegaard delta-peak signal-to-noise ratio improvements ranging from 1.3 to 11.6 dB for lossy compression in the 0.125 to 2.00 bpp range and bit-rate reductions of up to 1.6 bpp for lossless compression.
With the advent of modern computing and imaging technologies, the use of digital holography became practical in many applications such as microscopy, interferometry, non-destructive testing, data encoding, and certification. In this respect the need for an efficient representation technology becomes imminent. However, microscopic holographic off-axis recordings have characteristics that differ significantly from that of regular natural imagery, because they represent a recorded interference pattern that mainly manifests itself in the high-frequency bands. Since regular image compression schemes are typically based on a Laplace frequency distribution, they are unable to optimally represent such holographic data. However, unlike most image codecs, the JPEG 2000 standard can be modified to efficiently cope with images containing such alternative frequency distributions by applying the arbitrary wavelet decomposition of Part 2. As such, employing packet decompositions already significantly improves the compression performance for off-axis holographic images over that of regular image compression schemes. Moreover, extending JPEG 2000 with directional wavelet transforms shows even higher compression efficiency improvements. Such an extension to the standard would only require signaling the applied directions, and would not impact any other existing functionality. In this paper, we show that wavelet packet decomposition combined with directional wavelet transforms provides efficient lossy-to-lossless compression of microscopic off-axis holographic imagery.
Publisher’s Note: This paper, originally published on 9/26/2013, was replaced with a corrected/revised version on
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Significant research efforts have been invested in attempting to reliably capture and visualize holograms since their
inception in 1962. However, less attention has been given to the efficient digital representation of the recorded
holograms, which differ considerably from digitally recorded photographs. This paper examines the properties of
recorded off-axis holograms and attempts to find a suitable sparse representation for holographic data. Results show
significantly improved Bjøntegaard delta PSNR of over 4.5 dB on average within a bit-rate range of 0.125 to 2 bpp when
combining the direction-adaptive discrete wavelet transform with non-standard decomposition schemes for off-axis
holographic recordings; up to 7.5% reduction of file size has been achieved in the lossless case.
Significant research has been performed on the use of directional transforms for the compression of still imagery, in
particular on the application of block-based and segmentation driven directional adaptive discrete wavelet transforms.
However, all of the proposed methodologies suffer from the extra side-information that needs to be encoded. This
encoding overhead and added complexity is unfortunately not negligible. This paper describes various considerations
and trade-offs that were made during the search towards a practical solution for using directional adaptive transforms in
still image coding. We propose two codec instantiations respectively based upon quadtree-coding (QT-L) and
JPEG 2000's EBCOT engine and discuss various experimental results.
In this paper, we examine the rate-distortion performance in terms of perceptual quality of JPEG XR (ISO/IEC 29199-2 |
ITU-T Rec. T.832)1 and earlier standardized image compression algorithms such as JPEG (ISO/IEC 10918-1 | ITU-T
Rec. T.81)2 and JPEG 2000 (ISO/IEC 15444-1 | ITU-T Rec. T.800)3. Unfortunately, objective visual quality metrics (like
MSE, PSNR, VQM, SSIM, etc.) do not always correlate well with the actual perceived image quality. In some specific
cases, it is even possible that certain visible coding artifacts remain undetectable by these objective visual quality tests.
As such, we conducted a series of subjective visual quality assessment tests to measure the visual performance of JPEG
XR, JPEG 2000 and JPEG. This paper describes the design of the subjective visual quality assessment experiments,
addressing the encountered difficulties and potential pitfalls. Our results indicate that for high bit-rates (i.e. more than 1
bpp) all three codecs more or less have an equal overall performance. However, as expected, at lower bit-rates JPEG
performs significantly weaker for every tested image than JPEG 2000 and JPEG XR. On the other hand, both JPEG 2000
and JPEG XR appear to be very competitive at these low bit-rate ranges. Only for specific image content types (e.g.
smooth gradient surfaces), JPEG XR appears to have some difficulties. Nevertheless, discarding the fact that JPEG 2000
offers more functionality features than JPEG XR, the latter performed very good for most images and almost in par with
JPEG 2000. As a conclusion, the results of the subjective visual quality assessment tests show that JPEG XR
successfully passed our verification experiments for low dynamic range imagery.
The Joint Photographic Experts Group (JPEG) committee is a joint working group of the International Standardization
Organization (ISO) and the International Electrotechnical Commission (IEC). The word "Joint" in JPEG however does
not refer to the joint efforts of ISO and IEC, but to the fact that the JPEG activities are the result of an additional
collaboration with the International Telecommunication Union (ITU). Inspired by technology and market evolutions, i.e.
the advent of wavelet technology and need for additional functionality such as scalability, the JPEG committee launched
in 1997 a new standardization process that would result in 2000 in a new standard: JPEG 2000. JPEG 2000 is a
collection of standard parts, which together shape the complete toolset. Currently, the JPEG 2000 standard is composed
out of 13 parts. In this paper, we review these parts and additionally address recent standardization initiatives within the
JPEG committee such as JPSearch, JPEG-XR and AIC.
The JPEG2000 standard is currently widely adopted in medical and volumetric data compression. In this respect, a 3D
extension (JPEG2000 Part 10 - JP3D) is currently being standardized. However, no suitable 3D context model is yet
available within the standard, such that the context-based arithmetic entropy coder of JP3D still uses the 2D context
model of JPEG2000 Part 1. In this paper, we propose a context design algorithm that, based on a training set, generates
an optimized 3D context model, while avoiding an exhaustive search and at the same time keeping the space and time
complexities well within the limits of today hardware. The algorithm comes as a solution for the situations in which the
number of allowable initial contexts is very large. In this sense, the three-dimensional 3x3x3 context neighborhood
investigated in this paper is a good example of an instantiation that would have otherwise been computationally
unfeasible. Furthermore, we have designed a new 3D context model for JP3D. We show that the JP3D codec equipped
with this model consistently outperforms its 2D context model counterpart, for an extended test dataset. In this respect,
we report a gain in lossless compression performance of up to 10%. Moreover, for a large range of bitrates, we always
obtain gains in PSNR, sometimes even over 3dB.
The size of medical data has increased significantly over the last few years. This poses severe problems for the rapid
transmission of medical data across the hospital network resulting into longer access times of the images. Also longterm
storage of data becomes more and more a problem. In an attempt to overcome the increasing data size often
lossless or lossy compression algorithms are being used.
This paper compares the existing JPEG2000 compression algorithm and the new emerging JP3D standard for
compression of volumetric datasets. The main benefit of JP3D is that this algorithm truly is a 3D compression algorithm
that exploits correlation not only within but also in between slices of a dataset. We evaluate both lossless and lossy
modes of these algorithms.
As a first step we perform an objective evaluation. Using RMSE and PSNR metrics we determine which compression
algorithm performs best and this for multiple compression ratios and for several clinically relevant medical datasets. It
is well known that RMSE and PSNR often do not correlate well with subjectively perceived image quality. Therefore
we also perform a psycho visual analysis by means of a numerical observer. With this observer model we analyze how
compression artifacts actually are perceived by a human observer. Results show superior performance of the new JP3D
algorithm compared to the existing JPEG2000 algorithm.