One of the most frequently used coding mode in H.264 is skip mode. In the conventional approach, after the best RD
mode has been computed and the resultant predicted error coefficients block is all quantized to zero, it is switched to
skip mode. This is a waste of computational resources because skip mode doesn't require forward transform and
quantization. In this paper, skip mode condition is checked for the macroblock prior to multi-block motion estimation.
Motion estimation will not be performed if the condition is satisfied which will drastically reduce the computations. The
condition considers zero-block property after 4x4 block transform/quantisation and caters for noise inherent in natural
video images. In addition, color components are also taken into consideration for skip mode decision. The experimental
results show that the approach can improve encoder speed greatly with negligible bit rate increase or PSNR degradation.
KEYWORDS: Video, Scalable video coding, Switches, Internet, Data storage, Network architectures, Signal to noise ratio, Computer programming, Data storage servers, Multimedia
In this paper, we consider the delivery of layered video from parallel heterogenous servers within a video-on-demand
infrastruture. A parallel server architecture enables the service of requests by more than one server, thus
reducing load at individual servers and dispersing network load. Serving requests for a single video through all
or a subset of servers in the system reduces the probability of server overload brought about by a large number of
requests for popular content; more clients may also be admitted for the retrieval of video data. Delivery through
multiple servers requires that the video data be partitioned. Ideally, the data should be partitioned such that
multiple server retrieval provides the same download and access time performance possible when retrieving from
a single server of the same total bandwidth. We design and analyse play-while-retrieve strategies that involve
streaming layers from different servers and show how access time can be reduced through these strategies. While
system wide data striping can completely remove the problem of hotspotting, the method does not scale well
and problems may be encountered when the system grow in size or when heterogenous disks have to be used.
Since our proposed scheme takes into consideration heterogenous upload bandwidth and layer bitrates, it may
be suitable for a peer to peer network where peer upload bandwidth is limited and varied.
In spatial error concealment (SEC), methods like bilinear interpolation (BI) and directional interpolation (DI) are commonly used to estimate the missing pixel values resulting from losses occurring in video streams. Despite being able to preserve spatial smoothness, BI produces a blurring effect and is unable to preserve structural information. DI produces spurious edges in regions with no strong edges, resulting in visible artefacts. In this paper, we propose a SEC algorithm that addresses the above drawbacks by formulating a weighted sum of candidate macroblocks produced from DI and BI, with weights derived adaptively through local information. We demonstrate that the proposed algorithm offers visual improvements over both DI based algorithms and the SEC algorithm based on BI in the H.264/AVC reference software JM 12.0. Most importantly, this unique approach preserves edge information and spatial smoothness in the error concealed macroblock due to the integration of both BI and DI.
KEYWORDS: Motion estimation, Computer programming, Video, Video coding, Quantization, Diamond, Standards development, Video processing, Distortion, Digital signal processing
It is well known that motion estimation is the most computationally intensive processing unit of the H.264 video
encoder. Various fast motion estimation algorithms have been proposed to reduce its complexity. Generally, these
approaches achieve speedup by reducing the number of candidate search points within the search window. In this paper,
we propose a new method, which uses the Sum-of-Absolute-Differences mapping (SAD map) to dynamically cache the
SAD values and then reuse them for different block sizes. Experimental results on standard video sequences verified
that the proposed method is capable of increasing the encoder speed by up to 15% without any loss in PSNR value or
increase in bit rate. Due to its generic nature, this method can be applied in any fast motion estimation methods although
it is especially effective in the full search motion estimation method.
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