问题 单项选择题

多媒体数据可以进行压缩的依据是信息量等于()。

A.数据量与冗余量之和

B.数据量与冗余量之差

C.数据量与存储量之和

D.数据量与存储量之差

答案

参考答案:B

解析:

本题考查多媒体数据压缩的可能性。

视频是由一帧一帧的图像组成的,图像的各像素之间,无论在行方向还是在列方向,都存在着一定的相关性,即冗余度。应用某种编码方法提取或减少冗余度,便可以达到压缩数据的目的。根据题意,多媒体数据可以进行压缩的依据是信息量等于数据量与冗余量之差。

常见的图像数据冗余情况介绍如下。

(1)空间冗余

空间冗余是静态图像存在的最重要的一种数据冗余。一般通过改变物体表面颜色的像素存储方式来利用空间连贯性,达到减少数据量的目的。

(2)时间冗余

时间冗余是序列图像(电视图像、运动图像)表示中经常包含的冗余。序列图像是位于一时间轴区间内的一组连续画面,其中的相邻帧往往包含相同的背景和移动物体,这种共同性是由于相邻帧记录了相邻时刻的同一场景画面。

(3)结构冗余

在许多图像的纹理区,图像的像素值存在明显的分布模式,或是图像的各个部分存在强相似性。

(4)知识冗余

有些图像的理解与某些基础知识有相当大的相关性。根据已有的知识,对某些图像中所包含的物体,可以构造其基本模型,并创建对应各种特征的图像库,进而图像的存储只需要保存一些特征参数,从而可以大大减少数据量。知识冗余是模型编码主要利用的特征。

(5)视觉冗余

人类的视觉系统对于图像的感知是非均匀和非线性的,人眼对一般图像中的许多信息并不敏感,并不是对图像中的任何变化都能察觉到。然而在获取原始图像数据时,通常假定视觉系统是线性的和均匀的,对视觉敏感与否不进行设定,这样就会产生比较多的数据,这就是视觉冗余。

(6)图像区域的相同性冗余

它是指图像中的两个或多个区域所对应的所有像素值相同或相近而产生的数据重复性存储,这就是图像区域的相似性冗余。

(7)纹理的统计冗余

有些图像纹理尽管不严格服从某一分布规律,但是它在统计的意义上服从该规律。利用这种性质也可以减少表示图像的数据量,所以称之为纹理的统计冗余。

阅读理解

阅读理解。

根据短文内容,从短文后的选项中,选出能填入空白处的最佳选项。选项中有两项为多余选项。

     My mother is a diligent and kind woman. She is very busy from morning till night. As a teacher, she

works hard.    1    Both my brother and I love her dearly as she loves us.

My mother has been teaching math at a middle school in my hometown. She goes to work early in the

morning and does not return home until late in the afternoon.    2    She treats them with patience and

teaches them well. For her excellent quality and very good teaching results, she has been elected as a

model teacher several times.

       3  .  Every day, when she comes back home from work, she sets about doing housework, sweeping

the living room and bedrooms or cleaning the furniture, and putting everything in good order. She seems

to be busy all the time. As she has been very busy working every day, she looks older than her age. But

she looks as cheerful and happy as ever. Mother never buys expensive dresses for herself, but she often

buys some inexpensive but high quality clothes for us.    4    She just eats a plain meal outside when she is

too busy to cook herself. She lives a busy yet simple life, without any complaints.

     Often she says to us, "work while you work, and play while you play. That is the way to be happy

and gay. If you do not work, you will become lazy and be of no use to society". What a piece of good

advice this is!    5  .  This advice of hers will always serve as a guide to my behavior. My mother is great

indeed, and I always feel proud of her.

A. She enjoys listening to classic music.

B. As a mother, she takes good care of us and gives us every comfort.

C. She loves her students and cares for them.

D. She never goes to expensive restaurants to enjoy meals.

E. My mother is hard-working and never wastes money.

F. I never forget it and always bear it in my mind.

G. Can you tell us something about your mother?

单项选择题