Standard Video Codecs Research Articles

POCS-based error concealment for packet video using multiframe overlap information

This paper proposes a new error concealment algorithm for packet video, effectively eliminating error propagation effects. Most standard video codecs use motion compensation to remove temporal redundancy. With such motion-compensated interframe processing, any packet loss may generate serious error propagation over more than ten consecutive frames. This kind of error propagation leads to perceptually annoying artifacts. Thus, proper error concealment algorithms need to be used to reduce this effect. The proposed algorithm adopts a one-pixel block overlap structure. With the redundancy information from the damaged frame and the following frames, the proposed POCS-based method can have consistently high performance in error concealment. According to the experimental results, the proposed algorithm can successfully eliminate visible error propagation. In addition, the proposed algorithm is very robust. Experimental results show that it can have good error concealment results, even when the damaged frame loses all the DCT coefficients.

Adaptive Early Jump-Out Technique for Fast Motion Estimation in Video Coding

An adaptive early jump-out technique for speeding up the block-based motion estimation is proposed. By using the new technique, we can speed up the full range search several times without losing the picture quality significantly. The proposed technique can also be embedded in almost all the existing fast motion estimation algorithms to speed up the computation further. Since the proposed technique can be embedded in the existing motion estimation algorithms, it can be applied to almost all the standard video codecs, such as the MPEG coder, and improve the coding speed of such codecs significantly. Our technique has been tested on the H.261, the H.263, and the MPEG-I codecs, and the coding speed does improve significantly.

Postprocessing of late cells for packet video

A method for preventing accumulation of image artifacts due to cell loss in packet video is presented. At each ATM switching node an auxiliary buffer is used to store the overflow traffic of the main switching buffer. The main buffer is served with an absolute priority over the auxiliary buffer. Decoded pictures are normally reconstructed from the cells of the main buffer. The late cells received from the auxiliary buffer are processed and properly added to the current decoded picture. Postprocessing of these cells for the standard video codecs such as H.261 and MPEG is presented. It is shown that although the picture quality due to cell loss is temporarily degraded, it is immediately brought back to its original quality upon the reception of the late cells, as if no loss has occurred.

Low bit-rate video coding with spatio-temporal geometric transforms

A low bit-rate video coding technique that uses spatio-temporal geometric transforms is presented. Motion compensation based on the bilinear transform is employed to reduce the temporal redundancy of the video. The spatial redundancy of the motion compensated error images is reduced by a combination of fractal and DCT. It is shown that in the objects boundaries of the motion compensated error image fractal outperforms DCT, while in the smooth areas DCT is better than fractal. A hybrid combination of fractal and DCT gives the best result. The performance of this hybrid codec with geometrically transformed motion compensation is compared against the H.261 standard video codec at 64 kbit/s.

Investigation of a visual telephone prototyping on personal computers

An investigation of a visual telephone prototyping is presented. All the related standards such as system requirements, video codec, and speech codec are introduced. Since the most time-consuming task is video encoding, more details about the H.263 video codec standard are explained. In addition, the strategies for real-time transmission and processing are discussed. From the simulation results, the suggested prototype on personal computers shows the potential on multimedia communication for consumer products.

An adapted H.261 two-layer video codec for ATM networks

An adaptive video codec which can maintain compatibility between the existing digital circuit switched networks and future ATM networks is described. It is based on two-layer coding principles, where in the base layer the H.261 standard video codec is employed. It is shown that a discrete cosine transform (DCT) in the second layer is unnecessary and can be replaced by a simple requantizer which finely quantizes the residue quantization distortions of the transform coefficients of the base layer. Characteristics of this quantizer in terms of nature of quantization and step sizes are studied. Efficient coding and addressing of residual distortions are described. Finally, a two-dimensional variable length code for the quantized residual distortions is given.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>