Showing papers by "Mitsuji Muneyasu published in 2008"

Acoustic Echo Cancellation Algorithm Tolerable for Double Talk

Abstract: This paper proposes a step size control method capable of steadily canceling acoustic echo resisting double talk. The method is characterized by applying a sub-adaptive filter to the control. The step size and the number of taps of the sub- adaptive filter are larger and fewer than those of the main adaptive filter used for canceling the acoustic echo, respectively. Accordingly, the sub-adaptive filter can reduce the residual echo more rapidly than the main adaptive filter. The proposed method applies the step size calculated using the residual echo to the main adaptive filter, and thereby, quickly and steadily reduces the acoustic echo. This paper finally verifies that the proposed method can provide almost the same convergence speed as that obtained by applying a fixed large step size to the main adaptive filter.

Speech separation based on law of causality

Abstract: This paper proposes a microphone array system separating speech signals, based on a different principle from independent component analysis (ICA). This system applies linear prediction error filters to microphone outputs, and using the prediction errors, adjusts the coefficients of adaptive filters. In this case, only the prediction errors satisfying the low of causality become available for the adjustment; consequently, this system can steer a null toward a direction satisfying it. The permutation problem discussed in ICA can be thereby avoided. This system also can compensate the separated speech signals by using adaptive filters, and finally, can provide high quality speech signals. This paper moreover verifies the performance of the proposed system by using speech signal data measured in an ordinary room. This result shows that the proposed system works well even in reverberation environment.

A New Progressive Image Quality Control Method for ROI Coding in JPEG2000 Standard

Abstract: JPEG2000 still image coding standard has a feature called Region of Interest (ROI) coding. This feature can encode a restricted region in an image prior to than its background (BG) region. In low bit rate compression, the code of the ROI region occupies the most of the bit stream in the whole image and it causes the serious deterioration of the image quality in the BG region. This paper proposes a new image quality control method between the ROI region and the BG one by the one time encoding process and it can achieve more detailed image quality control. The use of ROI masks in the encoder makes it possible. The standard decoder of JPEG2000 part1 can decode the encoded data in the proposed method.