Peak Signal-to-noise Ratio Improvement Research Articles

다시점 비디오 부호화를 위한 움직임벡터 예측값 선택 방법

본 논문에서는 JVT에서 표준화가 진행 중인 다시점 비디오 부호화의 부호화 효율을 높이기 위해 다시점 비디오의 예측구조의 특성을 고려하여 움직임벡터 예측값을 선택하는 방법을 제안한다. 다시점 비디오 부호화에서 시간 방향과 뷰 방향의 예측을 수행하면서 서로 다른 성향의 움직임벡터가 발생된다. 또한 주변 블록에서 시간 방향과 뷰 방향 참조의 움직임벡터가 혼재하는 상황에서 동일한 성향의 움직임벡터가 선택되지 않는 경우가 발생되어 움직임벡터의 예측 효율이 저하된다. 이에 다시점 비디오 부호화의 예측구조에 따라 움직임벡터 예측값을 선택할 수 있는 방법을 제안한다. 제안하는 움직임벡터 예측값 선택 방법을 통하여 다시점 비디오 부호화의 압축 효율을 높일 수 있었으며, JMVM 3.6에서 움직임벡터 예측값을 선택하는 방법을 사용하는 다시점 비디오 부호화와 비교하여 PSNR(Peak Signal-to-Noise Ratio)이 약<TEX>$0.03{\sim}0.1$</TEX> dB 정도 향상되었다. In this paper, we propose a method to select motion vector predictor by considering prediction structure of a multi view content for coding efficiency of multi view coding which is being standardized in JVT. Motion vector of a different tendency is happened while carrying out temporal and view reference prediction of multi-view video coding. Also, due to the phenomena of motion vectors being searched in both temporal and view order, the motion vectors do not agree with each other resulting a decline in coding efficiency. This paper is about how the motion vector predictor are selected with information of prediction structure. By using the proposed method, a compression ratio of the proposed method in multi-view video coding is increased, and finally <TEX>$0.03{\sim}0.1$</TEX> dB PSNR(Peak Signal-to-Noise Ratio) improvement was obtained compared with the case of JMVM 3.6 method.

Enhancing video error resilience by using data-embedding techniques

In this paper, error-resilient video coding schemes based on data-embedding techniques are proposed for the H.263+ codec. Data embedding, popularly applied to secret hiding and digital watermarking, is now used to convey error recovery information to the decoder via a covert channel, without causing significant increase in transmission bitrate. Our embedded information provides implicit macroblock (MB) delimiters for resynchronization in presence of channel errors. In this way, the decoder is capable of isolating erroneous MBs with the extracted information. A set of variational schemes is proposed, extensively analyzed, and compared to the competitive counterparts (e.g., the original H.263+ TMN8 and its synchronization-enhanced version) at the same bitrate. Experimental results show that our data embedding process decreases the average peak signal-to-noise ratio (PSNR) in error-free conditions by 0.3 dB (light data embedding) to 1.8 dB (heavy data embedding), but it is capable of achieving a significant PSNR improvement up to 2 and 9.5 dB when the bit error rate is 10/sup -5/ and 10/sup -3/, respectively. We also provide suggestions of how to adaptively apply the proposed schemes for different channel error conditions and different video contents.

Frame bit allocation for the H.264/AVC video coder via Cauchy-density-based rate and distortion models

Based on the observation that a Cauchy density is more accurate in estimating the distribution of the ac coefficients than the traditional Laplacian density, rate and distortion models with improved accuracy are developed. The entropy and distortion models for quantized discrete cosine transform coefficients are justified in a frame bit-allocation application for H.264. Extensive analysis with carefully selected anchor video sequences demonstrates a 0.24-dB average peak signal-to-noise ratio (PSNR) improvement over the JM 8.4 rate control algorithm, and a 0.33-dB average PSNR improvement over the TM5-based bit-allocation algorithm that has recently been proposed for H.264 by Li et al. The analysis also demonstrates 20% and 60% reductions in PSNR variation among the encoded pictures when compared to the JM 8.4 rate control algorithm and the TM5-based bit-allocation algorithm, respectively.

Coordinated application of multiple description scalar quantization and error concealment for error-resilient MPEG video streaming

Historically, multiple description coding (MDC) and postprocessing error concealment (ECN) algorithms have evolved separately. In this paper, we propose a coordinated application of multiple description scalar quantizers (MDSQ) and ECN, where the smoothness of the video signal helps to compensate for the loss of descriptions. In particular, we perform a reconstruction that is consistent with the data received at the decoder. When only a single description is available, the video is reconstructed in such a way that: 1) if we were to regenerate two descriptions (from the reconstructed video), one of them would be equivalent to the received description and 2) the reconstructed video is spatiotemporally smooth. Experimental results with several video sequences demonstrated a peak signal-to-noise ratio (PSNR) improvement of 0.9-2.8 dB for intracoded frames. The PSNR improvements for intercoded frames were negligible. However, for both cases, the visual improvements were much more striking than what the PSNR improvement suggested.

Pengolahan Citra Obyek dari Balik Penghambur dengan Metoda Optik (Tapis Ruang) dan Metoda Digital (“Or Minimum”)

In this paper, optical and digital methods are combined to improve the quality of the image obtained through a scattering medium. The optical method, using simply an imaging positive lens and a small circular spatial filter, succeded in the first stage to form an observable image. Two criteria were adopted to evaluate the quality of the image in the optical method. The first is Peak Signal-to-Noise Ratio (PSNR), the second is the correlation coefficient between the original image and the processed scattered image. It was found that PSNR decreased at a larger diameter of the spatial filter. The optimum correlation coefficient (0.368) was found at a filter diameter of 1.6 mm. Next, the digital image processing was conducted using the assumption that the scattering medium always moved randomly. Involving different diameters of the spatial filter, the image was recorded with a CCD camera connected to a computer. For each diameter, the image was recorded many times, each time with a different position of the scattering medium. The images were then processed with the so-called “or minimum” and the averaging method. In the “or minimum” method, the gray level of the same pixel position of all images was compared to find its minimum value. The ensemble of pixels having the minimum gray level constitutes a new image. In the averaging method, the average gray level in each pixel position was computed from a number of images. It appeared that the “or minimum” method yielded the best improvement in PSNR (the largest being 4.00 dB) compared to the averaging method (1.04 dB). The improvement of the correlation coefficient was up to 0.072 in the “or minimum” method and 0.05 in the averaging method.

Multi-path selection for multiple description video streaming over overlay networks

Real-time media distribution over the Internet poses several challenging problems due to its stringent delay/loss requirements and complex network dynamics. A promising approach to alleviate the severe impacts of these dynamics is to transmit the media over diverse paths. For such an environment, multiple description (MD) coding has been previously proposed to produce multiple independently decodable streams that are routed over partially link–disjoint (non-shared) paths for combatting bursty packet losses and error propagation. However, selecting these paths appropriately is fundamental to the success of MD streaming and path diversity. Hence, in this paper we develop models for MD streaming over multiple paths and based on these models we propose a multi-path selection method that chooses a set of paths maximizing the overall quality at the client under various constraints. The simulation results with MPEG-2 show that sizeable average peak signal-to-noise ratio (PSNR) improvements (ranging from 0.73 to 6.07 dB) can be achieved when the source video is streamed over intelligently selected multiple paths as opposed to over the shortest path or maximally link–disjoint paths. In addition to the PSNR improvement, end-users experience a more continual, i.e., uninterrupted, streaming quality. Our work also considers the architecture and mechanisms by which multi-path streaming can be accomplished over a conventional IP network.

Error-rate-based power-controlled multimode H.263-assisted video telephony

The performance of a power-control algorithm suitable for multimode transceivers is investigated using 1, 2, and 4 bit/symbol modems. It is shown that the algorithm is suitable for maintaining a target frame error-rate (FER), irrespective of the modulation mode employed. The transceiver parameters are summarized in Table I, while the minimum and maximum required average transmitted powers in the cell for the different modes are given in Table V. Given the video bit rates of 4.25-16.9 kbps in the various modem modes, the corresponding average video peak signal-to-noise ratio (PSNR) improvement of approximately 6 dB can be inferred from the figure included, where the corresponding PSNR values are approximately 32.5, 35, and 38.5 dB, respectively. This PSNR improvement is achievable in cell areas, where the average transmitted power levels of Table V can be maintained, supporting one of the above legitimate modes of operation of the multimode transceiver.

Frame interpolation and bidirectional prediction of video using compactly encoded optical-flow fields and label fields

We consider the problems of motion-compensated frame interpolation (MCFI) and bidirectional prediction in a video coding environment. These applications generally require good motion estimates at the decoder. We use a multiscale optical-flow-based motion estimator that provides smooth, natural motion fields under bit-rate constraints. These motion estimates scale well with change in temporal resolution and provide considerable flexibility in the design and operation of coders and decoders. In the MCFI application, this estimator provides excellent interpolated frames that are superior to those of conventional motion estimators, both visually and in terms of peak signal-to-noise ratio (PSNR). We also consider the effect of occlusions in the bidirectional prediction application and introduce a dense label field that complements our motion estimator. This label field enables us to adaptively weight the forward and backward predictions and gives us substantial visual and PSNR improvements in the covered/uncovered regions of the sequence.

Interlaced to progressive scan conversion for HD-MAC application

A multilevel nonlinear filter for simultaneous edge detection and noise suppression called a nested median filter/median averaging filter (NMF/MAF) pair is introduced. On the basis of the NMF/MAF pair, an interlaced-to-progressive (I/P) conversion is proposed to estimate motion vectors in the 40-ms mode of the HD-MAC system. Test results for HD-MAC applications confirmed that the proposed I/P conversion scheme was robust in preserving sharp edges, inhibiting edge shifting, and suppressing impulsive noise. The motion compensation interpolated HD-MAC image sequence with the proposed I/P conversion scheme showed 4 approximately 6 dB to the improvement in peak SNR (peak signal-to-noise ratio) compared to the interlaced scheme. A structural overview for implementation of the NMF/MAF integrated circuit is described. The features of this circuit are an integrated dynamic RAM based on horizontal line memories, a high-speed bubble sorter, and a window option circuit. >