Sharif Digital Repository

This paper introduces a novel scalable speech coding scheme based on embedded matrix quantization of LSF parameters in an LPC model. In the proposed quantizer, codewords are organized based on a tree structure through a cell-merging process, which leads to a fine-grain scalable coder at rates below 900 bps. Near natural sounding is achieved at very low rates by employing an efficient adaptive dual-band scheme to approximate the LPC excitation signals. Evaluation results, obtained from both overall quality measurement and intelligibility assessment, show that the proposed coder could be a reasonable choice for improving the bottom-line speech quality in low bit rates. © 2008 IEEE  

Fractional-pixel accuracy Motion Estimation (ME) has been shown to result in higher quality reconstructed image sequences in hybrid video coding systems. However, the higher quality is achieved by notably increased Motion Field (MF) bitrate and more complex computations. In this paper, new half-pixel block matching ME algorithms are proposed to improve the rate-distortion characteristics of low bitrate video communications. The proposed methods tend to decrease the required video bandwidth, while improving the motion compensation quality. The key idea is to put a deeper focus on the search origin of the ME process, based on center-bias characteristics of low bitrate video MFs. To employ the... 

In recent years, the demand for video transmission over wireless communication networks is growing very fast. The H.264 video compression standard which offers high quality at low bit rates, is a suitable codec for applications that require efficient video transmission over wireless networks. While the compressed videos are transmitted through error-prone networks, error robustness becomes an important issue. In this paper, a joint source-channel Lagrange optimization method in which the distortion of the decoder is estimated without using feedback which can be used for both multicast and point-to-point applications is proposed. The experimental results show that the new algorithm has a good...