Current Issue : April - June Volume : 2012 Issue Number : 2 Articles : 5 Articles
This article proposes a real-time test and verification system for full-reference automatic image quality assessment\r\nand verification of digital TV sets. Digital camera is used for acquisition of the TV screen content in order to ensure\r\nquality assessment of the content as perceived by the user. Test has been executed in three steps: image\r\nacquisition by camera, TV screen content extraction and full-reference image quality assessment. The TV screen\r\ncontent is extracted from the captured image in two steps: detection of the TV screen edge and transformation of\r\nthe TV screen content to dimensions of the reference image. Three image comparison methods are incorporated\r\nto perform full-reference image quality assessment. Reference image for quality assessment is obtained either by\r\ngrabbing the image from TV set or by capturing the TV screen content on the golden sample. Digital camera was\r\nlater replaced with DSP-based camera for image acquisition and algorithm execution which brought significant\r\nperformance improvements. The comparison methods were tested under constant and variable illumination\r\nconditions. The proposed system is used to automate the verification step on the final production line of digital TV\r\nsets. The time required for verification step decreased by a factor of 5 when using the proposed system on the\r\nfinal production line instead of a manual one....
In this article, we propose a multiple-input-multiple-output, orthogonal frequency division multiplexing, codedivision\r\nmultiple-access (MIMO OFDM-CDMA) scheme. The main objective is to provide extra flexibility in user\r\nmultiplexing and data rate adaptation, that offer higher system throughput and better diversity gains. This is done\r\nby spreading on all the signal domains; i.e, space-time frequency spreading is employed to transmit users� signals.\r\nThe flexibility to spread on all three domains allows us to independently spread users� data, to maintain increased\r\nsystem throughput and to have higher diversity gains. We derive new accurate approximations for the probability\r\nof symbol error and signal-to-interference noise ratio (SINR) for zero forcing (ZF) receiver. This study and simulation\r\nresults show that MIMO OFDM-CDMA is capable of achieving diversity gains significantly larger than that of the\r\nconventional 2-D CDMA OFDM and MIMO MC CDMA schemes....
Image fusion is a fundamental technique for integrating high-resolution panchromatic images and low-resolution\r\nmultispectral (MS) images. Fused images may enhance image interpretation. Empirical mode decomposition (EMD)\r\nis an effective method of decomposing non-stationary signals into a set of intrinsic mode functions (IMFs). Hence,\r\nthe characteristics of EMD may apply to image fusion techniques. This study proposes a novel image fusion\r\nmethod using a pyramid-based EMD. To improve computational time, the pyramid-based EMD extracts the IMF\r\nfrom the reduced layer. Next, EMD-based image fusion decomposes the panchromatic and MS images into IMFs.\r\nThe high-frequency IMF of the MS image is subsequently replaced by the high-frequency IMF of the panchromatic\r\nimage. Finally, the fused image is reconstructed from the mixed IMFs. Two experiments with different sensors were\r\nconducted to validate the fused results of the proposed method. The experimental results indicate that the\r\nproposed method is effective and promising regarding both visual effects and quantitative analysis....
This article proposes an efficient median filter based algorithm to remove transient noise in a speech signal. The\r\nproposed algorithm adopts a modified long-term predictor (LTP) as the pre-processor of the noise reduction\r\nprocess to reduce speech distortion caused by the nonlinear nature of the median filter. This article shows that the\r\nLTP analysis does not modify to the characteristic of transient noise during the speech modeling process.\r\nOppositely, if a short-term linear prediction (STP) filter is employed as a pre-processor, the enhanced output\r\nincludes residual noise because the STP analysis and synthesis process keeps and restores transient noise\r\ncomponents. To minimize residual noise and speech distortion after the transient noise reduction, a modified LTP\r\nmethod is proposed which estimates the characteristic of speech more accurately. By ignoring transient noise\r\npresence regions in the pitch lag detection step, the modified LTP successfully avoids being affected by transient\r\nnoise. A backward pitch prediction algorithm is also adopted to reduce speech distortion in the onset regions.\r\nExperimental results verify that the proposed system efficiently eliminates transient noise while preserving desired\r\nspeech signal....
This article proposes an efficient two-channel time delay estimation method for tracking a moving speaker in noisy\r\nand re-verberant environment. Unlike conventional linear regression model-based methods, the proposed multiple\r\nlinear regression model designed in the expanded phase domain shows high estimation accuracy in adverse\r\ncondition because its the Gaussian assumption on phase distribution is valid. Therefore, the least-square-based\r\ntime delay estimator using the proposed multiple linear regression model becomes an ideal estimator that does\r\nnot require a complicated phase unwrapping process. In addition, the proposed method is extended to the twostage\r\nrecursive estimation approach, which can be used for a moving source tracking scenario. The performance of\r\nthe proposed method is compared with that of conventional cross-correlation and linear regression-based\r\nmethods in noisy and reverberant environment. Experimental results verify that the proposed algorithm\r\nsignificantly decreases estimation anomalies and improves the accuracy of time delay estimation. Finally, the\r\ntracking performance of the proposed method to both slow and fast moving speakers is confirmed in adverse\r\nenvironment....
Loading....