18 research outputs found
Revisiting the Sample Adaptive Offset post-filter of VVC with Neural-Networks
The Sample Adaptive Offset (SAO) filter has been introduced in HEVC to reduce
general coding and banding artefacts in the reconstructed pictures, in
complement to the De-Blocking Filter (DBF) which reduces artifacts at block
boundaries specifically. The new video compression standard Versatile Video
Coding (VVC) reduces the BD-rate by about 36% at the same reconstruction
quality compared to HEVC. It implements an additional new in-loop Adaptive Loop
Filter (ALF) on top of the DBF and the SAO filter, the latter remaining
unchanged compared to HEVC. However, the relative performance of SAO in VVC has
been lowered significantly. In this paper, it is proposed to revisit the SAO
filter using Neural Networks (NN). The general principles of the SAO are kept,
but the a-priori classification of SAO is replaced with a set of neural
networks that determine which reconstructed samples should be corrected and in
which proportion. Similarly to the original SAO, some parameters are determined
at the encoder side and encoded per CTU. The average BD-rate gain of the
proposed SAO improves VVC by at least 2.3% in Random Access while the overall
complexity is kept relatively small compared to other NN-based methods
Latent-Shift: Gradient of Entropy Helps Neural Codecs
End-to-end image/video codecs are getting competitive compared to traditional
compression techniques that have been developed through decades of manual
engineering efforts. These trainable codecs have many advantages over
traditional techniques such as easy adaptation on perceptual distortion metrics
and high performance on specific domains thanks to their learning ability.
However, state of the art neural codecs does not take advantage of the
existence of gradient of entropy in decoding device. In this paper, we
theoretically show that gradient of entropy (available at decoder side) is
correlated with the gradient of the reconstruction error (which is not
available at decoder side). We then demonstrate experimentally that this
gradient can be used on various compression methods, leading to a rate
savings for the same quality. Our method is orthogonal to other improvements
and brings independent rate savings.Comment: Published to ICIP2023, 6 pages, 1 figur
Machine Learning based Efficient QT-MTT Partitioning Scheme for VVC Intra Encoders
The next-generation Versatile Video Coding (VVC) standard introduces a new
Multi-Type Tree (MTT) block partitioning structure that supports Binary-Tree
(BT) and Ternary-Tree (TT) splits in both vertical and horizontal directions.
This new approach leads to five possible splits at each block depth and thereby
improves the coding efficiency of VVC over that of the preceding High
Efficiency Video Coding (HEVC) standard, which only supports Quad-Tree (QT)
partitioning with a single split per block depth. However, MTT also has brought
a considerable impact on encoder computational complexity. In this paper, a
two-stage learning-based technique is proposed to tackle the complexity
overhead of MTT in VVC intra encoders. In our scheme, the input block is first
processed by a Convolutional Neural Network (CNN) to predict its spatial
features through a vector of probabilities describing the partition at each 4x4
edge. Subsequently, a Decision Tree (DT) model leverages this vector of spatial
features to predict the most likely splits at each block. Finally, based on
this prediction, only the N most likely splits are processed by the
Rate-Distortion (RD) process of the encoder. In order to train our CNN and DT
models on a wide range of image contents, we also propose a public VVC frame
partitioning dataset based on existing image dataset encoded with the VVC
reference software encoder. Our proposal relying on the top-3 configuration
reaches 46.6% complexity reduction for a negligible bitrate increase of 0.86%.
A top-2 configuration enables a higher complexity reduction of 69.8% for 2.57%
bitrate loss. These results emphasis a better trade-off between VTM intra
coding efficiency and complexity reduction compared to the state-of-the-art
solutions
Designs and Implementations in Neural Network-based Video Coding
The past decade has witnessed the huge success of deep learning in well-known
artificial intelligence applications such as face recognition, autonomous
driving, and large language model like ChatGPT. Recently, the application of
deep learning has been extended to a much wider range, with neural
network-based video coding being one of them. Neural network-based video coding
can be performed at two different levels: embedding neural network-based
(NN-based) coding tools into a classical video compression framework or
building the entire compression framework upon neural networks. This paper
elaborates some of the recent exploration efforts of JVET (Joint Video Experts
Team of ITU-T SG 16 WP 3 and ISO/IEC JTC 1/SC29) in the name of neural
network-based video coding (NNVC), falling in the former category.
Specifically, this paper discusses two major NN-based video coding
technologies, i.e. neural network-based intra prediction and neural
network-based in-loop filtering, which have been investigated for several
meeting cycles in JVET and finally adopted into the reference software of NNVC.
Extensive experiments on top of the NNVC have been conducted to evaluate the
effectiveness of the proposed techniques. Compared with VTM-11.0_nnvc, the
proposed NN-based coding tools in NNVC-4.0 could achieve {11.94%, 21.86%,
22.59%}, {9.18%, 19.76%, 20.92%}, and {10.63%, 21.56%, 23.02%} BD-rate
reductions on average for {Y, Cb, Cr} under random-access, low-delay, and
all-intra configurations respectively
Intra-household use and acceptability of Ready-to-Use-Supplementary-Foods distributed in Niger between July and December 2010.
Few studies have looked at consumption of Ready-to-Use-Supplementary-Foods (RUSFs) during a nutritional emergency. Here, we describe the use and acceptability of RUSF within households in four districts of the region of Maradi, Niger during large scale preventive distributions with RUSF in 2010 targeted at children 6-35months of age. Our study comprised both quantitative and qualitative components to collect detailed information and to allow in-depth interviews. We performed a cross-sectional survey in 16 villages between two monthly distributions of RUSF (October-November 2010). All households with at least one child who received RUSF were included and a total of 1842 caregivers were interviewed using a structured questionnaire. Focus groups and individual interviews of 128 caregivers were conducted in eight of the selected villages. On average, 24.7% of households reported any sharing of RUSF within the household. Sharing practices outside the household remained rare. Most of the sharing reported occurred among children under 5years of age living in the household. On average, 91% of caregivers in all districts rated the child's appreciation of the products as good or very good. Program planning may need to explicitly accounting for the sharing of products among children under 5 within household
Sliding Adjustment for 3D Video Representation
<p/> <p>This paper deals with video coding of static scenes viewed by a moving camera. We propose an automatic way to encode such video sequences using several 3D models. Contrary to prior art in model-based coding where 3D models have to be known, the 3D models are automatically computed from the original video sequence. We show that several independent 3D models provide the same functionalities as one single 3D model, and avoid some drawbacks of the previous approaches. To achieve this goal we propose a novel algorithm of sliding adjustment, which ensures consistency of successive 3D models. The paper presents a method to automatically extract the set of 3D models and associate camera positions. The obtained representation can be used for reconstructing the original sequence, or virtual ones. It also enables 3D functionalities such as synthetic object insertion, lightning modification, or stereoscopic visualization. Results on real video sequences are presented.</p
Représentation 3D de séquences vidéo : (schéma d'extraction automatique d'un flux de modèles 3D, applications à la compression et à la réalité virtuelle)
RENNES1-BU Sciences Philo (352382102) / SudocSudocFranceF