In this paper, we propose the macroblock-level adaptive dynamic resolution conversion (DRC) technique usable by encoder to decide to reduce the resolution of input image on block-by-block basis for better compression efficiency. By reducing the spatial resolution of the block in the proposed scheme, it provides additional compression. As a proper resolution of a block is selected adaptively in the rate-distortion optimized way, more flexible coding is supported to adapt to the feature of image. Simulation based on the state of the art codec H.264 standard demonstrates that the proposed scheme has better performance than H.264 in terms of rate-distortion.
Compared to conventional video standards, the main features of H.264 standard are its high coding efficiency and its network friendliness. In spite of these outstanding merits, it is not easy to implement H.264 codec as a real-time system, due to its requirements of large memory bandwidth and intensive computation. Although the variable-block-size motion compensation using multiple reference frames is one of the key coding tools to bring about its main performance gain, its optimal use demands substantial computation for the rate-distortion calculation of all possible combinations of coding modes and estimation of the best motion vector. Many existing fast motion estimation algorithms are not suitable for H.264, which employs variable motion block sizes. We propose an adaptive motion search scheme utilizing the hierarchical block structure based on the deviation of subblock motion vectors. The proposed fast scheme adjusts the search center and search pattern according to the subblock motion-vector distribution.
The standardization for the scalable extension of H.264 has called
for additional functionality based on H.264 standard to support the
combined spatio-temporal and SNR scalability. For the entropy coding
of H.264 scalable extension, Context-based Adaptive Binary
Arithmetic Coding (CABAC) scheme is considered so far. In this
paper, we present a new context modeling scheme by using inter layer
correlation between the syntax elements. As a result, it improves
coding efficiency of entropy coding in H.264 scalable extension. In
simulation results of applying the proposed scheme to encoding the
syntax element mb_type, it is shown that improvement in
coding efficiency of the proposed method is up to 16% in terms of
bit saving due to estimation of more adequate probability model.
In this paper, we propose a multiple description coder for motion vector (MV-MDC) based on data partitioned bitstream of the H.264/AVC standard. The proposed multiple description (MD) encoder separates the motion vector (MV) into two parts having the same priority and transmits each part through an independent packet. The proposed MD decoding scheme utilizes two matching criteria to find the accurate MV estimate when one of the MV descriptions is lost. Simulation results show that compared to simply duplicated bitstream transmission, the proposed MV-MDC scheme reduces a large amount of data without serious visual quality loss of reconstructed picture.
The adaptive coding schemes in H.264 standard provide a significant coding efficiency and some additional features like error resilience and network friendliness. The variable block size motion compensation using multiple reference frames is one of the key H.264 coding elements to provide notable performance gain. However it is also the main culprit that increases the overall computational complexity. For this reason, this paper proposes a fast algorithm for variable block size motion estimation in H.264. In addition, we also propose a fast mode decision scheme by classifying modes based on rate-distortion cost. The experimental results show that the combined proposed methods provide significant improvement in processing speed without noticeable coding loss.