40327612
Dual-plan bandwidth smoothing for layer-encoded video
Traditional bandwidth smoothing techniques can be naturally supported by the renegotiated constant bit rate (RCBR) service model, but renegotiation failure in RCBR may cause buffer underflow and interrupt the playback of video. To address this concern, a novel dual-plan bandwidth smoothing (DBS) scheme is proposed in this paper by taking advantage of the SNR scalability of layer-encoded video. Upon renegotiation failure, the proposed scheme can adaptively discard certain enhancement layers to guarantee continuous video playback at the original frame rate. Experiments are carried out to demonstrate the validity of the proposed scheme. The impacts of renegotiation interval, granularity of enhancement layers, and playback buffer size on resulted video quality are also studied. From the simulation results, it is shown that the performance of the RCBR-based DBS scheme can be improved by 1) reducing the minimum time gap of renegotiation interval; 2) employing multilayer video encoding with finer granularity; and/or 3) increasing the playback buffer size.
9503765
Unequal-arm adaptive rood pattern search for fast block-matching motion estimation in the JVT/H.26L
The adaptive rood pattern search (ARPS) algorithm proposed by Nie and Ma (2002) has shown two to three times of search speed-up improvement over that of diamond search (DS) based on the MPEG-4 verification model encoding platform. In this paper, first we have shown that the distribution of motion vectors bears a rood shape. An improved ARPS algorithm, called ARPS-3 or unequal-arm ARPS, is then proposed and experimented on the JVT/H.26L JM encoding platform. Due to complex modes and multiframe prediction, a new normalized computational cost metrics is also proposed for objectively measuring the computational gain or search speed-up. Experimental results show that ARPS-3 has achieved superb performance on many accounts while maintaining fairly close rate-distortion performance compared with that of the full search. It also outperforms its predecessors, ARPS and ARPS-2 (or equal-arm ARPS).
1533691
Generalized optimum dynamic bit allocation scheme for source compression
Dynamic bit allocation directly impacts the overall coding performance in block transform (e.g., DCT, Hadamard, etc.) coding, subband coding, and wavelet coding. In very low bit rate coding (such as the evolving MPEG-4 standard), additional factors impacting the bit allocation process need to be identified and properly exploited to achieve optimal coding performance. In the paper, a generalized optimum dynamic bit allocation algorithm is presented. The algorithm is based on the Shannon rate-distortion bound and a weighted distortion criterion using a Lagrange multiplier optimization technique. The results look promising for applications in real-time multimedia communications.<<ETX>>
35556766
Error concealment for image transmission by multiscale Markov random field modeling
Transmission of visual data over communication channels introduces serious fidelity problems. The paper proposes an efficient error concealment algorithm for the image transmitted as encoded bitstreams. The proposed method introduces a multiscale Markov random field (MMRF) to model the original image. The established MMRF model is consequently employed to interpolate the missing blocks in the observing data via maximum a posterior (MAP) estimation. Compared with the conventional spatial interpolation scheme, this algorithm offers significant improvements on both subjective and objective qualities of the recovered image.
9933284
A MCMC approach for Bayesian super-resolution image reconstruction
In this paper, we consider the super-resolution image reconstruction problem. We propose a Markov chain Monte Carlo (MCMC) approach to find the maximum a posterior probability (MAP) estimation of the unknown high-resolution image. Firstly, Gaussian Markov random field (GMRF) is exploited for modeling the prior probability distribution of the unknown high-resolution image. Then, a MCMC technique (in particular, the Gibbs sampler) is introduced to generate samples from the posterior probability distribution to compute the MAP estimation of the unknown high-resolution image, which is obtained as the mean of the samples. Moreover, we derive a bound on the convergence time of the proposed MCMC approach. Finally, the experimental results are presented to verify the superior performance of the proposed approach and the validity of the proposed bound.
14032639
Sliding-window packetization for unequal loss protection based multiple description coding
Unequal loss protection (ULP) for transmitting embedded bitstream over packet erasure networks has been extensively studied. However, most of the existing works focused on rate-distortion optimization of individual encoding unit, e.g., a group of pictures (GOP), which may lead to noticeable video quality variations due to varying channel conditions. In this paper, a novel sliding-window packetization scheme is proposed, which combat bursty packet loss through GOP interleaving. Two levels of rate allocation are introduced: intra-GOP rate allocation minimizes the distortion of individual GOP, and provides hybrid FEC/retransmission packet loss recovery; while inter-GOP rate allocation intends to reduce video quality fluctuations by adaptively allocating bandwidth according to video signal characteristics. Through this way, more consistent video quality can be achieved under various packet loss probability, as verified by our experimental results.
5064603
The ascending star subgraph decomposition of some star forests