Jae-Kyoon Kim

Video frame rate control for non-guaranteed network services with explicit rate feedback

An adaptive video frame rate control method is proposed for the network of time-varying rate channel with explicit rate feedback. It consists of a prediction module of future channel rate and an adaptive frame discarding and skipping module. We derive an encoder buffer constraint which guarantees an end-to-end delay bound of video frames. The recursive least-squares (RLS) method is used as a tool to predict the low frequency component of channel rate. The adaptive frame discarding method prevents delay violation of frames due to the channel rate prediction error. Also, the frame skipping method adapts the encoder output rate to the channel rate while keeping a constant level of video quality. From the simulation result, it is shown that the proposed method keeps the decoded image quality nearly constant with much less number of skipped frames and no delay violating frame during the congestion period.

A motion-adaptive de-interlacing method

The authors describe an improved motion-adaptive de-interlacing method that incorporates the missing lines of interlaced fields from pixels of the same field or adjacent fields after motion compensation. Some improvements were obtained by suppressing the effect of false motion caused by interpolation error in the searched field, and by interpolation filtering based on the characteristics of moving objects. Experimental data show that the proposed method resulted in smaller interpolation error than conventional de-interlacing methods. >

Rate control algorithm for fast bit-rate conversion transcoding

In this paper, a new rate control algorithm is introduced as a solution for fast rate control requirements in transcoding. The specific transcoding problem mentioned in this paper is referred to as bit-rate conversion. For video services in heterogeneous network environments, it is necessary to convert the bit-rate of a compressed video to match it to transmission channels of lower capacity. The transcoding of coded video streams by requantization in the DCT (discrete cosine transform) domain is considered as a promising technique for its low complexity and acceptable picture quality. We carried out extensive simulations for many kinds of video sequences to find a novel R-Q (rate-quantization) model in the requantization process and found a piecewise linearly decreasing model. Exploiting this model we propose an efficient rate control algorithm for fast transcoding. Since the proposed algorithm requires much lower complexity than conventional algorithms and inherently avoids additional steps of implementation for a scene adaptive rate control in the transcoder, it has a significant advantage as a rate control algorithm for transcoding.

Fast motion vector re-estimation for transcoding MPEG-1 into MPEG-4 with lower spatial resolution in DCT-domain

In this paper, we propose a fast motion vector re-estimation for transcoding MPEG-1 to MPEG-4 with lower spatial resolution. This task can be performed in the pixel-domain or in the discrete cosine transform (DCT) domain. In this paper, we concentrate on the DCT-domain approach, which requires lower delay and complexity than those in the pixel-domain. For the DCT-domain transcoding to lower spatial resolution pictures, DCT-domain down-sampling filter is applied and a base motion vector (BMV) for the down-sampled MPEG-4 macroblock is to be calculated from the input motion vectors operating on the higher spatial resolution image. Quality can be significantly improved by refining the BMV. Starting with the BMV, the motion vector refinement (MVR) scheme searches for a delta motion vector within a significantly reduced search area. We propose a fast MVR scheme for video down-sampling in the DCT-domain based on minimizing the number of required check points, and a computationally efficient method for extracting motion compensated DCT block. We also show an efficient scheme for selecting a coding mode for a macroblock in the lower resolution video from those of the corresponding higher resolution video.

The analysis of a multiserver queue fed by a discrete autoregressive process of order 1

Based on matrix analytic methods and the theory of Markov regenerative processes, we obtain the stationary distributions of the system size and the waiting time in a multiserver queue into which packets arrive according to a discrete autoregressive process of order 1.

Data partitioning and coding of DCT coefficients based on requantization for error-resilient transmission of video

In this paper, we propose an efficient data partitioning and coding algorithm for an error-resilient transmission of DCT coefficients in error prone environment. In the typical data partitioning for Inter-coded frames, motion and macroblock header information is separated from the texture information. It can be an effective tool for the transmission of video over the error prone environment. For Intra-coded frames, however, the loss of DCT coefficients is fatal because there is no other information to reconstruct the corrupted macroblocks by errors. Conventional data partitioning algorithm for DCT coefficients is to separate a fixed number of the significant DCT coefficients from the remaining coefficients, called the spectral separation. While the spectral separation can guarantee an error resilient transmission with small overhead, the main drawback is a significant decrease in the image quality of the high priority partition, compared with that of the bitstreams without data partitioning for an equivalent bit-rate. In the proposed scheme, the quantized DCT coefficients are partitioned into an even-value approximation and the odd remainder part. We also propose a simple and efficient coding algorithm for the odd remainder part. It is shown that the proposed algorithm provides a better image quality than the conventional methods with a little overhead.

A new vertex-based binary shape coder for high coding efficiency

Abstract This paper proposes a new vertex-based binary shape intra coding scheme that generates a set of vertices reducing shape reconstruction error and efficiently encodes the vertices. The conventional vertex-based coding scheme uses the iterated refinement method (IRM) for vertex selection and the object-adaptive vertex encoding (OAVE) for vertex transmission. In the proposed scheme, we introduce a vertex adjustment method to be applied to the vertices selected by the IRM. The vertex adjustment method significantly reduces the reconstruction error of binary shapes. For efficient transmission of vertices, we also propose 1D vertex detection, vertex reordering and initial vertex encoding methods. Furthermore, a conditional differential chain coding is presented for efficient lossless coding of contours. Experimental results show that the proposed vertex-based intra coding scheme reduces coded bits by 17–29% compared with the conventional vertex-based coding scheme, and by up to 27% compared with the intra coding mode of the context-based arithmetic encoding (CAE) scheme of the MPEG-4 Video Verification Model.

Design and performance analysis of hierarchical location management strategies for wireless mobile communication systems

In this paper, we propose three hierarchical location management strategies for wireless mobile communication systems. The first one is home server first (HSF) scheme in which callees location is queried at callees home location server first. Next, we propose least-common-ancestor server first (LSF) scheme in which a search starts at the least-common-ancestor server of callers current location and callees home server. Finally, we propose distributed LSF in which the location management is made on 2-layered distributed structure. We evaluate the performance of the proposed schemes and compare it with that of another hierarchical scheme proposed by Wang (J.Z. Wang, A fully distributed location registration strategy for universal personal communication systems, IEEE J. Select. Areas Commun., 11(6) (1993) 850-860) and IS-41-based scheme. It is shown that the proposed schemes have reduced location management cost and that the cost is less affected by the increment of communication cost than the compared schemes.

Mobile location management strategy with implicit location registration

We propose a new location management strategy by introducing the concept of implicit location registration. Implicit location registration is triggered whenever a transaction occurs between the backbone network and a mobile terminal. The mobiles most recently notified cell and its neighboring cells are paged to locate a mobile. It is shown that the proposed strategy has the lower paging cost than the simultaneous paging scheme. In addition, the proposed strategy can further reduce the paging cost when the terminal mobility is low and when there are many transactions between the backbone network and mobile terminals.

Scene adaptive bit-rate control method on MPEG video coding

This paper presents a simple bitrate control method to percent the abrupt quality degradation after scene change. After scene change, the quality degradation occurs due to the poor temporal prediction between pictures before and after scene change. We predict the coding complexity of picture using the spatial variance before DCT and spectral flatness measure. From the predicted coding complexity, we show that the rate-distortion relation of image can be approximated to exponential function. When scene changes, picture target bit is adjusted in the direction to minimize the distortion in a GOP using the rate-distortion relations for each P-picture. Since the bit shortage could be occurred, proposed method extends the current GOP to the next. The algorithm can be applied to the existing MPEG codecs and real-time applications easily. Compared with the MPEG-2 TM5 rate control algorithm, proposed algorithm shows 0.5 to approximately 2.5 dB gain in PSNR and a small fluctuation in quality after scene change.