Keunsoo Park

A fast mode selection scheme in inter-layer prediction of H.264 Scalable Extension coding

We propose a fast inter-layer mode decision method by utilizing coding information of base layer upward its enhancement layer in scalable video coding (SVC), also called MPEG-4 part 10 Advanced Video Coding Amendment 3 or H.264 Scalable Extension (SE). In this paper, when the motion vectors from the base layer have zero motion (0, 0) in inter-layer motion prediction or the Integer Transform coefficients of the residual between current MB and the motion compensated MB by the predicted motion vectors from the base layer are all zero, the block mode of the corresponding block to be encoded in the enhancement layer is determined to be the 16*16 mode. In addition, if the predicted mode of the MB to be encoded at the enhancement layer is not equal to the 16 *16 mode, then the rate-distortion optimization is only performed on the reduced numbers of candidate modes which are same or smaller partitioned modes. Our proposed method exhibits the complexity reduction in encoding time up to 70%. Nevertheless, it shows negligible PSNR degradation and bit rate increase up to 0.2 MB and 0.71 % respectively.

A network-adaptive SVC Streaming Architecture

For video streaming, we must consider terminal and network characteristics. The scalable video coding (SVC) can represent video bitstreams in different scalable layers for flexible adaptation to terminal and network characteristics. The SVC can allow for extraction of appropriate partial bitstreams to meet specific target bitrates and spatial resolutions from an SVC bitstream with several spatial, temporal and quality scalability layers. Moreover, the extraction process is fast, so it is possible to extract the partial video streams online to cope with the delivery networks with changing characteristics such as bandwidth etc. With all the advantages of SVC, we design and implement a network-adaptive SVC streaming system to extract partial SVC bitstreams to meet the required target bitrates and spatial resolutions. We present the implementation of our SVC streaming system with experimental results.

An efficient block mode decision for temporal scalability in scalable video coding

In this paper, a fast intermode decision scheme which is suitable for the hierarchical B-picture structure in which much computational power is spent for combined variable block sizes and bi-predictive motion estimation is introduced. The hypothesis testing considering the characteristics of the hierarchical B-picture structure in the proposed method is performed on 16x16 and 8x8 blocks to have early termination for RD computation of all possible modes. The early termination in intermode decision is performed by comparing the pixel values of current blocks and corresponding motion-compensated blocks. When the hypothesis tests are performed, the confidence intervals to accept the null hypothesis or not are decided according to the temporal scalability levels under the consideration of properties of hierarchical B-pictures. The proposed scheme exhibits effective early termination behavior in intermode decision of temporal scalabilities and leads to a significant reduction up to 69% in computational complexity with slight increment in bit amounts. The degradation of visual quality turns out to be negligible in terms of PSNR values.

A fast 4x4 intra mode decision for inter frame coding in H.264|MPEG-4 Part 10

The H.264\MPEG-4 Part 10 (AVC) standard incorporates an intra prediction into inter frame coding. However, this leads to excessive increase of encoding time. This paper presents a fast intra mode decision and intra prediction algorithm to reduce encoding time. Basically, the proposed algorithm designs the skip condition for candidate modes of 4times4 intra prediction to be dependent of the content types of sequences and the context of pre-encoded adjacent blocks in terms of intra prediction-related probabilities. The content and context adaptive conditional probability table for the most probable modes is generated during an I- frame coding and is exploited for the intra mode decision in the following P frames until the next I-frame. The experimental results show that the total encoding time saving can be achieved up to maximally 43.17% with negligible PSNR drop and bitrate increase compared to the joint model (JM) reference software of AVC.

Dependent Quantization for Scalable Video Coding

Quantization in video coding plays an important role in controlling the bitrate of compressed bitstreams to adjust with the allowed bandwidth of delivery networks and storage. Since scalable video coding (SVC) being currently standardized exhibits highly dependent coding nature not only between frames but also in the lower and higher layers, we propose a dependent quantization scheme for SVC and compare its performance in visual qualities and bitrates with the current technique in JSVM reference software. The experimental results show that the dependent quantization outperforms the current technique in JSVM reference software with 0.5 ~ 1.25 dB PSNR increment or 5 ~ 20% bits saving for the enhancement layer of SVC.

A Fast 4X4 Intra Prediction Method using Motion Vector Information and Statistical Mode Correlation between 16X16 and 4X4 Intra Prediction In H.264|MPEG-4 AVC

H.264| MPEG-4 AVC is a new video codingstandard defined by JVT (Joint Video Team) which consists of ITU-T and ISO/IEC. Many techniques are adopted fur the compression efficiency: Especially, an intra prediction in an inter frame is one example but it leads to excessive amount of encoding time due to the decision of a candidate mode and a RDcost calculation. For this reason, a fast determination of the best intra prediction mode is the main issue for saving the encoding time. In this paper, by using the result of statistical relation between intra and intra predictions, the number of candidate modes for intra prediction is reduced. Firstly, utilizing motion vector obtained after inter prediction, prediction of a block mode for each macroblock is made. If an intra prediction is needed, the correlation table between and intra predicted modes is created using the probability during each I frame-coding process. Secondly, using this result, the candidate modes for a intra prediction that reaches a predefined specific probability value are only considered in the same GOP For the experiments, JM11.0, the reference software of H.264|MPEG-4 AVC is used and the experimental results show that the encoding time could be reduced by 51.24% in maximum with negligible amounts of PSNR drop and bitrate increase.

Selective Inter-layer Residual Prediction Coding and Fast Mode Decision for Spatial Enhancement Layers in Scalable Video Coding

In order to reduce the complexity of SVC encoding, we introduce a fast mode decision method in the enhancement layers of spatial scalability by selectively performing the inter-layer residual prediction of SVC. The Inter-layer residual prediction coding in Scalable Video Coding has a large advantage of enhancing the coding efficiency since it utilizes the correlation between two residuals from a lower spatial layer and its next higher spatial layer. However, this entails the dramatical increase in the complexity of SVC encoders. The proposed method is to analyze the characteristics of integer transform coefficients for the subtracted signal for two residuals from lower and upper spatial layers. Then it selectively performs the inter-layer residual prediction coding and rate-distortion optimizations in the upper spatial enhancement layer if the SAD values of residuals exceed adaptive threshold values. Therefore, by classifying the residuals according to the properties of integer-transform coefficients only with SAD of residuals between two layers, the SVC encoder can perform the inter-layer residual coding selectively, thus significantly reducing the total required encoding time. The proposed method results in reduction of the total encoding time with 51.5% in average while maintaining the RD performance with negligible amounts of quality degradation.

Fast All-Zero Block Detection Based on Classification Approach

The AVC|H.264 video coding standard adopts 4x4 integer transform on residuals between an original pixel block and its motion-compensated pixel block to make better prediction for the improvement of temporal redundancy reduction. Detecting all-zero blocks prior to integer transform in AVC|H.264 was taken into account as an important step in fast encoding process. Different from the previous approaches to early detection of all-zero blocks based on sums of absolute differences and quantization steps, this paper designed a linear classifier with additional features available before integer transform. With significant features to detect all-zero IT coefficients, the linear classifier improved detection accuracy so that skipping the integer transform process could accelerate the encoding process and minimize the encoding performance drop in PSNR values. The linear classifier is trained with large amount of training data and tested by video sequences with different characteristics. Experimental results demonstrated that through a wide range of quantization parameters and video sequences the proposed approach improved detection of all-zero blocks over the conventional approach with negligible amounts of PSNR degradation.

A Fast Inter-layer Mode Decision Method inScalable Video Coding

We propose a fast inter-layer mode decision method by utilizing coding information of base layer upward its enhancement layer inscalable video coding (SVC), also called MPEG-4 part 10 Advanced Video Coding Amendment 3 or H.264 Scalable Extension (SE) which is being standardized. In this paper, when the motion vectors from the base layer have zero motion (0, 0) in inter-layer motion prediction or the Integer Transform coefficients of the residual between current MB and the motion compensated MB by the predicted motion vectors from the base layer are all zero, the block mode of the corresponding block to be encoded at the enhancement layer is determined to be the mode. In addition, if the predicted mode of the MB to be encoded at the enhancement layer is not equal to the mode, then the rate-distortion optimization is only performed on the reduced candidated modes which are same or smaller partitioned modes. Our proposed method exhibits the complexity reduction in encoding time up to 72%. Nevertheless, it shows negligible PSNR degradation and bit rate increase up to 0.25dB and 1.73%, respectively.

An Intra Prediction Method and Fast Intra Prediction Method in Inter Frames using Block Content and Dependency Probabilities on neighboring Block Modes in H.264|AVC

The H.264|AVC standard incorporates an intra prediction tool into inter frame coding. However, this leads to excessive amount of increase in encoding time, thus resulting in the difficulty in real-time implementation of software encoders. In this paper, we first propose an early decision on intra prediction coding and a fast intra prediction method using the characteristics of block contents and the context of neighboring block modes for the intra prediction in the inter frame coding of H.264/AVC. Basically, the proposed methods determine a skip condition on whether the intra prediction is to be used in the inter frame coding by considering the content characteristics of each block to be encoded and the context of its neighboring blocks. The performance of our proposed methods is compared with the Joint Model reference software version 11.0 of H.264|AVC. The experimental results show that our proposed methods allow for 41.63% reduction in the total encoding time with negligible amounts of PSNR drops and bitrate increases, compared to the original Joint Model reference software version 11.0.