Marta Karczewicz

Adaptive deblocking filter

This paper describes the adaptive deblocking filter used in the H.264/MPEG-4 AVC video coding standard. The filter performs simple operations to detect and analyze artifacts on coded block boundaries and attenuates those by applying a selected filter.

Low-complexity transform and quantization in H.264/AVC

This paper presents an overview of the transform and quantization designs in H.264. Unlike the popular 8/spl times/8 discrete cosine transform used in previous standards, the 4/spl times/4 transforms in H.264 can be computed exactly in integer arithmetic, thus avoiding inverse transform mismatch problems. The new transforms can also be computed without multiplications, just additions and shifts, in 16-bit arithmetic, thus minimizing computational complexity, especially for low-end processors. By using short tables, the new quantization formulas use multiplications but avoid divisions.

The SP- and SI-frames design for H.264/AVC

This paper discusses two new frame types, SP-frames and SI-frames, defined in the emerging video coding standard, known as ITU-T Rec. H.264 or ISO/IEC MPEG-4/Part 10-AVC. The main feature of SP-frames is that identical SP-frames can be reconstructed even when different reference frames are used for their prediction. This property allows them to replace I-frames in applications such as splicing, random access, and error recovery/resilience. We also include a description of SI-frames, which are used in conjunction with SP-frames. Finally, simulation results illustrating the coding efficiency of SP-frames are provided. It is shown that SP-frames have significantly better coding efficiency than I-frames while providing similar functionalities.

Improved h.264 intra coding based on bi-directional intra prediction, directional transform, and adaptive coefficient scanning

In this paper, a novel intra coding scheme is proposed. The proposed scheme improves H.264 intra coding from three aspects: 1) H.264 intra prediction is enhanced with additional bi-directional intra prediction modes; 2) H.264 integer transform is supplemented with directional transforms for some prediction modes; and 3) residual coefficient coding in CAVLC is improved. Compared to H.264, together the improvements can bring on average 7% and 10% coding gain for CABAC and for CAVLC, respectively, with average coding gain of 12% for HD sequences.

Transform Coefficient Coding in HEVC

This paper describes transform coefficient coding in the draft international standard of High Efficiency Video Coding (HEVC) specification and the driving motivations behind its design. Transform coefficient coding in HEVC encompasses the scanning patterns and coding methods for the last significant coefficient, significance map, coefficient levels, and sign data. Special attention is paid to the new methods of last significant coefficient coding, multilevel significance maps, high-throughput binarization, and sign data hiding. Experimental results are provided to evaluate the performance of transform coefficient coding in HEVC.

A Hybrid Video Coder Based on Extended Macroblock Sizes, Improved Interpolation, and Flexible Motion Representation

This paper describes a video coding technology proposal submitted by Qualcomm in response to a joint call for proposals (CfP) issued by ITU-T SG16 Q.6 (VCEG) and ISO/IEC JTC1/SC29/WG11 (MPEG) in January 2010. The proposed video codec follows a hybrid coding approach based on temporal prediction, followed by transform, quantization, and entropy coding of the residual. Some of its key features are extended block sizes (up to 64 × 64), single pass switched interpolation filters with offsets, mode-dependent directional transforms for intra-coding, luma and chroma high precision filtering, geometric motion partitions, adaptive motion vector resolution and efficient 16-point transforms. It also incorporates internal bit-depth increase and modified quadtree-based adaptive loop filtering. Simulation results are presented to demonstrate the high compression efficiency achieved by the proposed video codec at the expense of moderate increase in encoding and decoding complexity compared to the advanced video coding standard (AVC/H.264). For the random access and low delay configurations, it achieved average bit rate reductions of 30.9% and 33.0% for equivalent peak signal-to-noise ratio, respectively, compared to the corresponding AVC anchors. The proposed codec scored highly in both subjective evaluations and objective metrics and was among the best-performing CfP proposals.

Synchronization-predictive coding for video compression: the SP frames design for JVT/H.26L

This paper discusses the new frame types considered for the video coding standard JVT/H26L developed jointly by ITU-T VCEG and ISO-IEC MPEG. The new frame types are called SP and SI-frames and provide functionalities in bitstream switching, splicing, random access, fast forward, fast backward and error resilience/recovery. Specific applications are illustrated as examples on how the properties of SP and SI-frames can be exploited. Later, detailed descriptions of SP and SI-frame decoder and encoder are provided.

Low-complexity transform and quantization with 16-bit arithmetic for H.26L

This paper presents an overview of the latest transform and quantization designs for H.26L. Unlike the popular discrete cosine transform (DCT) used in previous standards, the transforms in H.26L can be computed exactly in integer arithmetic, thus avoiding inverse transform mismatch problems. The new transforms can also be computed without multiplications, just additions and shifts, in 16-bit arithmetic, thus minimizing computational complexity, especially for low-end processors. By using short tables, the new quantization formulas use multiplications but avoid divisions.

ECG data compression by spline approximation

Abstract A novel and efficient transform method for ECG data compression based on B-spline basis functions is proposed. The algorithm allows these basis functions to adapt their shape to the nonstationary behavior of ECG signals. The number and shape of these basis functions are completely characterized by the number and location of the so-called knots. The position of the knots can effectively be coded using run-length coding. Therefore, the overhead data required to describe the way the B-spline basis functions vary in time can be neglected compared to the gain in compression achieved by adaptation. The quasi-periodic nature of the ECG signal is used in order to further reduce redundant information in the data. Low bit-rates of the order of 160–200 bits/s are achieved with very good quality of the reconstructed signal. The algorithm is compared with other transform-based schemes (DCT and DLT), and was found superior at any bit-rate.

Adaptive Loop Filtering for Video Coding

Adaptive loop filtering for video coding is to minimize the mean square error between original samples and decoded samples by using Wiener-based adaptive filter. The proposed ALF is located at the last processing stage for each picture and can be regarded as a tool to catch and fix artifacts from previous stages. The suitable filter coefficients are determined by the encoder and explicitly signaled to the decoder. In order to achieve better coding efficiency, especially for high resolution videos, local adaptation is used for luma signals by applying different filters to different regions or blocks in a picture. In addition to filter adaptation, filter on/off control at coding tree unit (CTU) level is also helpful for improving coding efficiency. Syntax-wise, filter coefficients are sent in a picture level header called adaptation parameter set, and filter on/off flags of CTUs are interleaved at CTU level in the slice data. This syntax design not only supports picture level optimization but also achieves a low encoding latency. Simulation results show that the ALF can achieve on average 7% bit rate reduction for 25 HD sequences. The run time increases are 1% and 10% for encoders and decoders, respectively, without special attention to optimization in C++ code.