Shinya Kadono

Frame-rate up-conversion using reliable analysis of transmitted motion information

We propose a new frame-rate up-conversion algorithm using a vector reliable analysis scheme that reduces artifacts caused by the use of inaccurately transmitted motion vectors (MVs). In conventional up-conversion algorithms using motion estimation (ME), ME is performed between two adjacent decoded frames to construct MVs that allow the frame to be interpolated, irrespective of the amount of calculation for ME required. On the other hand, in conventional up-conversion algorithms using transmitted MVs, the quality of the interpolated frame depends largely on the MV that is derived by the encoder. In our proposed scheme, transmitted MVs are first analyzed to decide whether or not they are usable for constructing interpolation frames. The interpolation method is then adaptively selected from three methods: local motion-compensated interpolation, global motion-compensated interpolation and frame-repeated interpolation. The proposed method provides high quality interpolated frames and decreases the volume of calculation needed, making it especially well suited to multimedia mobile devices that depend on low-power processing.

Tree structured hybrid intra prediction

This paper proposes a new method to generate intra prediction images in intra coding, tree structured hybrid intra prediction. When generating intra prediction images, the proposed method selects the most suitable one from intra prediction images generated using two methods, pixel-based and block-based intra prediction. This selection is performed on macroblock or sub macroblock level based on a rate distortion optimization scheme. In addition, information indicating which prediction method is selected is described in the bitstream using a tree structure. The proposed method is initially described, and then the results of evaluation experiments are shown by comparison to conventional methods. Evaluation is carried out by implementing the proposed method in an H.264-based intra picture codec. The results of evaluation confirm that the proposed method improves PSNR by up to nearly 0.7 dB compared to conventional methods over a wide range of bit rates.

Rationality of restricted re-quantization for efficient MPEG transcoding

A macroblock-based optimization method is described for selecting quantization parameters so as to reduce the re-quantization errors in MPEG transcoding. Analysis has shown that re-quantization using a parameter larger than the original input quantization parameter but smaller than twice the original causes significant information loss in transcoding. This problem can be avoided by using a parameter larger than twice the original. The optimization method was thus extended based on a rate-distortion model to enable the re-quantization parameter to be selected from ones larger than twice the original input quantization range. This improved method outperformed a typical non-optimized transcoding scheme, improving the PSNR by about 1 dB.

Complexity and memory reduction for high-quality interlace video coding in H.264/AVC

We propose two techniques for an H.264/AVC hardware encoder, maximum three reference fields selection and restriction of the number of MC size based on picture coding type. The proposed method can reduce complexity by more than 40% and the amount of memory by 25% without visual degradation.

A study on high efficiency coding of HDTV at 50 Mbps

High-efficiency techniques for encoding HDTV signals at 50 Mb/s are proposed. An adaptive chrominance interpolation method and an adaptive chrominance decimation method are discussed. It is shown that the distortion of decimation can be decreased and visible distortion can be reduced. Some pictures using these schemes were encoded by computer simulation, and it was confirmed that the processed pictures are adequate for consumer use. >

Technologies in MPEG-4 AVC FRExt for improving subjective picture quality in high-definition video compression

This work presents our new coding tools adopted by the latest MPEG-4 AVC standard, i.e., the fidelity range extensions amendment. These tools have significantly improved subjective picture quality especially for HD applications, e.g., the next-generation optical disc packaged media such as the Blu-ray disc (BD) ROM.

Optimization of requantization parameter for MPEG transcoding

This paper considers transcoding in which an MPEG stream is converted to a low-bit-rate MPEG stream, and proposes a method in which the transcoding error can be reduced by optimally selecting the quantization parameter for each macroblock. In transcoding with a low compression ratio, it is crucial to prohibit transcoding with a requantization parameter which is 1 to 2 times the quantization parameter of the input stream. Consequently, as the first step, an optimization method for the requantization parameter is proposed which cares for the error propagation effect by interframe prediction. Then, the proposed optimization method is extended so that the method can also be applied to the case of a high compression ratio in which the rate—distortion curve is approximated for each macroblock in the range of requantization parameters larger than 2 times the quantization parameter. It is verified by a simulation experiment that the PSNR is improved by 0.5 to 0.8 dB compared to the case in which a 6 Mbit/s MPEG stream is not optimized by twofold recompression.

Motion compensation method for moving pictures with binary shape

This paper describes a motion compensation method for arbitrarily shaped moving visual objects. To utilise both the inter-frame correlation and the texture-shape correlation, we use macroblock-based motion compensation for binary shape coding as well as texture coding. To efficiently achieve motion compensation for a moving binary shape, we introduce extra motion vectors for the shape coding in addition to the texture motion vectors, where the shape motion vectors are coded by referring to the texture motion vectors. The proposed method can successfully save more than 50% of the number of bits in comparison with the intra-only method. The effectiveness of the proposed method has been established through MPEG4 standardisation activity, and the proposed motion-compensation framework has been adopted by the MPEG-4 visual coding standard (ISO 14496-2).