標題: 以基因法則設計通道匹配向量量化之研究
Channdel-Matched Vector Quantization Based on Genetic Algorithm
作者: 吳建生
Wu, Chien-Sheng
張文輝
Chang Wen-Whei
電信工程研究所
關鍵字: 基因法則;通道匹配;向量量化;genetic algorithm;channel-matched;vector quantization
公開日期: 1997
摘要: 向量量化是一項重要的影音資料壓縮技術。然而傳統的碼書設計方式
,卻會在訓練的過程中陷入區域最佳值。本論文首先希望應用基因法則的
全域平行隨機搜尋特性,利用染色體配對與基因突變的遺傳演化設計更有
效的向量量化碼書。接著我們將基因演化的設計成功地延伸,以有效對抗
通道雜訊的碼書訓練。另外,我們也發現能匹配通道雜訊的碼字索引排列
也能減小碼字傳送的平均失真。針對這個索引配置問題,我們結合了二元
交換技術以及基因演算法則來求取最佳的索引配置,並妥善處理染色體編
碼模式,以避免基因配對與突變所衍生的不合法索引排列。在本論文的最
後,將我們發展的碼書訓練技術,應用在交大語音傳輸實驗室建構的電子
郵件語音轉換系統上。
Vector quantization (VQ) has been widely used in speech and
image coding for data compression. It operates by encoding a
sequence of input vectors with a codebook and by transmitting
the index of the nearest codevector to the receiver.Thus, the
effects of channel errors on transmitted codevector indices can
result in significant distortion in decoded vectors. In this
work we explore the benefits of genetic algorithm for use in
designing a VQ with increased robustness to channel errors. The
first part of this investigation is concerned with the accuracy
of the codebook training. The well-known GLA algorithm
iteratively updates the codebook according to the nearest
neighbor and centroid conditions. However, its simple downhill
search transitions can easily become trapped in local optima and
thus miss finding the globally optimal codebook. To compensate
this shortage, we develop a codebook training technique based on
the genetic algorithm. The main attraction of genetic algorithm
arises from the fact that the given search space is explored in
parallel by means of iterative modifications of a population of
potential solutions (chromosomes). An alternative approach to
achieving robustness is that of index assignment. Here the
redundancy-free error protection is achieved by using a hybrid
strategy which merges the most appealing features of two
algorithms, the genetic algorithm helps to identify the hills
and the binary switching algorithm goes and climbs them. To
match the index assignment problem, the encoding of chromosomes
must be carefully designed to eliminate the illegality of the
offsprings following the crossover and mutation operators.
Finally, we apply the enhanced VQ technique to develop a voiced
mail system that uses touch tones as input and synthetic speech
as output to provide remote telephone access to electronic
mails.
URI: http://140.113.39.130/cdrfb3/record/nctu/#NT860435034
http://hdl.handle.net/11536/63055
Appears in Collections:Thesis