• Journal of Korea Multimedia Society
• /
• v.7 no.9
• /
• pp.1246-1254
• /
• 2004

This paper presents a image coding method that is well adaptive to close-range video transmission because of its low titrate and simple coding procedure. At first, it reduces temporal redundancies by performing image DPCM between previous frame and current frame, and makes wavelet transformed image of this difference image. Then, the coefficients are quantized selectively by using the coefficient values of base level and mid-frequency level because inter-level redundancies are widely exists in multi-resolution images. Finally quantized coefficients are made iron the function that implies the target bitrate, the average coefficient energy, and the value of the level. The proposed method shows the effective Performance in the experiments using the continuous motion images and transition images.

• Journal of KIISE:Information Networking
• /
• v.29 no.6
• /
• pp.749-754
• /
• 2002

In this paper, We propose a titrate allocation method in which the bitrates of the videos for the lower layer are restricted by constant titrate, but those of the higher layer are assigned to have the uniform picture quality, for the multiplexing system of multiple spatial scalable video sources. We first find an approximated model of distortion-bitrate for the MPEG-2 spatial scalable video coding system, then we obtain the bitrate for each source to have constant distortion ratio among the sources by using the approximated model parameters for real-time simple implementation. It is shown by simulation that the proposed bandwidth allocation can keep almost constant picture Quality ratio among the sources of higher layer.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.12 no.8
• /
• pp.3856-3872
• /
• 2018

HTTP-based adaptive streaming (HAS) has recently been widely deployed on the Internet. In the HAS system, a video content is encoded at multiple bitrates and the encoded video content is segmented into small parts of fixed durations. The HAS client requests a video segment and stores it in the playout buffer. The rate adaptation algorithm employed in HAS clients dynamically determines the video bitrate depending on the time-varying bandwidth. Many studies have shown that an efficient rate adaptation algorithm is critical to ensuring quality-of-experience in HAS systems. However, existing algorithms have problems estimating the network bandwidth because bandwidth estimation is performed on the client-side application stack. Without the help of transport layer protocols, it is difficult to achieve accurate bandwidth estimation due to the inherent segment-based transmission of the HAS. In this paper, we propose an alternative approach that utilizes the playout buffer occupancy rather than using bandwidth estimates obtained from the application layer. We start with a queueing analysis of the playout buffer. Then, we present a buffer-aware rate adaptation algorithm that is solely based on the mean buffer occupancy. Our simulation results show that compared to conventional algorithms, the proposed algorithm achieves very smooth video quality while delivering a similar average video bitrate.

• Journal of Broadcast Engineering
• /
• v.10 no.3
• /
• pp.328-338
• /
• 2005

Technology for compressing low-bitrate multichannel audio coding is being standardized owing to the increasing need of consumer for multichannel audio contents. In this paper we propose the sound source location cue coding (SSLCC) for extremely compressing multichannel audio to be suitable at the narrow bandwidth transmission environment. To improve the compression capability of the conventional binaural cue coding(BCC), the SSLCC adopts the virtual source location information (VSLI) as a spatial cue parameter, a symmetric uniform quantizer, and Huffman coder. The objective and subjective assessment results show that the SSLCC provides lower bitrate and better audio quality than conventional BCC method.

• Journal of Broadcast Engineering
• /
• v.10 no.3
• /
• pp.348-356
• /
• 2005

In this paper, we propose a fast bitrate reduction transcoding method to convert a bitstream coded by H.264 into a lower bitrate H.264 bitstream. Block mode informations and motion vectors generated by H.264 decoder are used for probability-based block mode determination in the proposed transcoding method. And the motion vector reuse and motion vector refinement process are applied in the proposed transcoding. In the experiment results, the proposed methods achieves approximately 40 times improvement in computation complexity compared with the cascaded pixel domain transcoding, while the PSNR(Peak Signal to Noise Ratio) is degraded with only $0.1\~0.3$ dB.

• Journal of Broadcast Engineering
• /
• v.10 no.4 s.29
• /
• pp.488-504
• /
• 2005

In this paper, we propose a new bitrate control scheme to improve the quality of image encoded by SVC and to resolve the problems of conventional scheme. In JSVM2.0, bitrate of a frame is controlled by an initial quantization parameter and scaling factor that it hasdifferent value according to frame. Itis difficult to get the best of video quality at arbitrary bitrate because the conventional scheme has two defects. One is that we have to know proper initial QP's fur all sequences. Another is that QP's control skill for macroblocks is very inefficient. In this paper, we propose an efficient bit allocation algorithm to reduce the effect of the initial QP and to increase the efficiency of bit allocation by using proper QP's for macroblocks. In simulation results, it can be seen that using the proposed scheme enables the SVC encoder to control the bitrate by the macroblock unit and outperforms the conventional schemes in the respect of rate-distortion.

• Proceedings of the IEEK Conference
• /
• 2005.11a
• /
• pp.525-528
• /
• 2005

Adaptive streaming algorithm for the realtime video decoder that can be dynamically adaptable to the network channel status or terminal environment is described and performance analyzed. An LMS filter is used to predict the bitrate and predicted bitrate is used to optimize based prediction filter is used to adapt and optimize the quality of the decoded pictures. The quality of the output pictures are about 48dB.

• Journal of Korea Multimedia Society
• /
• v.20 no.3
• /
• pp.446-455
• /
• 2017

A color image compression based on saliency map was proposed. The proposed method provides higher quality in saliency blocks on which people's attention focuses, compared with non-saliency blocks on which the attention less focuses at a given bitrate. The proposed method uses 3 different quantization tables according to each block's saliency level. In the experiment using 6 typical images, we compared the proposed method with JPEG and other conventional methods. As the result, it showed that the proposed method (Qup=0.5*Qx) is about 3.1 to 1.2 dB better than JPEG and others in saliency blocks in PSNR at the almost similar bitrate. In the comparison of result images, the proposed one also showed less error than others in saliency blocks.

• Journal of Korea Multimedia Society
• /
• v.8 no.6
• /
• pp.744-752
• /
• 2005

When the multiple video sources are transmitted together through the channel of fixed bandwidth, an efficient picture quality control is necessary. This paper presents a joint picture quality control method to satisfy the user requirement by priority among the video sources. The better picture quality is assigned to the source of higher priority compared to lower priority. We obtain the bitrate for each source to have a required distortion level among the sources by using an approximate distortion-bitrate model for simple implementation. It is shown by simulation that the proposed bandwidth allocation method can keep almost the user-required picture quality among the sources in comparison to an independent bandwidth allocation method.

• The Transactions of the Korean Institute of Electrical Engineers D
• /
• v.51 no.7
• /
• pp.302-307
• /
• 2002

Digital watermarking is the technique, which embeds an invisible signal including signal including owner identification and copy control information into multimedia data such as audio, video, and images for copyright protection. A new MPEG watermark embedding algorithm using complex block effect based on the Human Visual System(HVS) is introduced in this paper. In this algorithm, $8{\times}8$ dark blocks are selected, and the watermark is embedded in the DC component of the discrete cosine transform(DCT) by using quantization and modulus calculation. This algorithm uses a blind watermark retrieval technique, which detects the embedded watermark without using the original image. The experimental results show that the proposed watermark technique is robust against MPEG coding, bitrate changes, and various GOP(Group of Picture) changes.