Digital Audio Amplifier Processing and Image Impulse Noise Removal
Date Issued
2005
Date
2005
Author(s)
Yeh, Chien-Hung
DOI
en-US
Abstract
As the multimedia getting more and more common and popular, many color images and video are largely produced and transmitted everyday and everywhere. For audio part, because original audio signal is so small and must be amplified. However, there is usually distortion at traditional analogy amplifier. Until 1970’s, new amplifier technique, which is Class D amplifier, has been developed. Class D audio amplifier has gained preponderance over analogy amplifier. Never the less, for some operations, there is still the room for improving.
On the other hand, for image processing, people are usually transfer video by using net due to popularity of the Internet. At the process of transmission, there is often some noise. In the past, people is use median filter for removal noise. But median filter may blur the image and it can’t effectively eliminate noise for heavy corrupted image. It is necessary to propose an effective method for removal noise while retain image details. Some techniques are proposed for improving median filter.
We divide this thesis into two parts. In part one, we first introduce the complete Class D amplifier processing. The first step of Class D amplifier processing is PWM process. The PCM-PWM conversion is necessary, but we can’t directly covert the PCM signal to NPWM signal. In tradition, we are use linear interpolation to estimate NPWM signal and there is exist distortion problem. For improve the performance of PCM-PWM conversion, some conversion algorithm is proposed. We will introduce those previous methods for conversion. These methods are very helpful to our thesis investigation. We will propose our algorithms for PCM-PWM conversion, including two algorithms. Our algorithm is based on up- sampling. Experimental result shows Class D amplifier by using PWM, which produced by our proposed parabolic interpolation method drastically, reduces crossover distortion while maintaining most of the linear interpolation efficiency.
In addition, we will analyze for image restoration. In the part two, we will review the characteristic of impulse noise and the principle of median filter. To study some Detect Noise Algorithm, and in last, we will propose a new De-Noising technique and further generalize this technique for color image processing. For Noise Detection, we propose two new methods, which are named as Gap Detection and Minimum Edge Median Detection. The former detects strong impulse noise in highly corrupted images and the latter can detect any type noise. Out detection is based on gap values, which are obtained through exploiting characteristics of impulsive noise. In addition, we present a new techniques, Dynamic Median Restoration, to remove noise that is detected by our noise detection. It is efficient, very fast, and can remove noise even when noise ratio is very high.
Subjects
數位音訊放大器
雜訊消除
Digital Audio D Amplifier
Noise Removal
Type
thesis
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