知识点一：视频格式，视频特性

1． Video Formats （视频格式）

    Video versions of the moving image are recorded on tape or disc,each packaged in forms that vary in size,shape,speed,recording method,and playback mechanism.The most common video formats are Videotape 、 Digital Video 、 DVD 、 Internet Vedio .

1.1 Videotape （录像带）

    The VHS1/2-inch format is the preferred medium for commercial distribution of moving images.

    Sayings:most of people have recorded a TV program on VHS for later or repeated viewing .

1.2 Digital Video （数字视频）

Advantages:

• The good quality of the image.It is the highest quality of image availabie,relying on 500 lines of resolution,double that of analog video.
• Editing can be done on a computer using software that makes it ease to manipulate the sequence of images.
• Finally,it is quick and easy to transfer video to the computer using a high-speed connection such as FireWire.

1.3 DVD （数字视盘）

    DVD (Digital Video Disk)， is a media offering digital storage and playback of full-motion video. DVD 的全称是 Digital Video Disk ，即数字视盘。

    Digital Video images can be manipulated (.e.g., content ,size ,and color can be changed ),stored, duplicated, and replaced without loss of quality.

    Video-based courses with multiple soundtracks can be aimed at different types of students.

    Sayings: The disc is the same physical size as an audio CD or a CD-ROM but can hold enough data for four full length feature films.

1.4 Internet Vedio （网络视频）

    Video also can be delivered via the internet, usually using streaming video.

    Sayings: The same technology can also be used with sound alone .streaming means that the file doesn ’ t have to be completely downloaded before it starts playing. Any video (or audio) materials can be delivered over the internet using then streaming technique. The content is not stored on your computer . It “ flows ” into your active memory, is displayed ( or played) , and then is erased.

2. Special Attributes of Vedio( 视频特性)

The basic attribute of motion media is the ability to manipulate temporal and spatial perspectives. 视频的基本特性是它可以对时间和空间进行特殊的处理，这些处理不仅能够体现出戏剧化、创造性的效果，在教学中也发挥了作用。

2.1 Manipulation of time （时间处理）

    Video permits use to increase or decrease the amount of time required to observe an event;

    (1)Compression of time 压缩时间： 花朵静静地绽放，星星划过夜空，由蚕蛹变成蝴蝶的过程；

    (2)Expansion of time 拉长时间： 利用慢镜头扩展观察事物的时间。

2.2 Manipulation of Space （空间处理）

    Motion media permit us to view phenomena in microcosm and macrocosm—that is, at extremely close range or from a vast distance. And video and live television allow us and our students to observe two events occurring simultaneously but many miles apart using split screen.

    Examples: students can view the earth from the space shuttle (macro view ) . At the other extreme ,the can observe cell division under a microscope (micro view).

2.3 Animation （动画）

    This is a technique in which the producer takes advantage of persistence of vision to give motion to otherwise inanimate objects .

    Think: What is persistence of vision ?

2.4 Understanding video conventions （理解视频表达规则）

    The devices and techniques use in video to manipulate time and space employ what are for most of is readily accepted conventions.

    Examples:we understand that the athlete whose jumps is stopped in midair is not actually frozen in space, that the flashback is not an actual reversal of our normal time continuum, that the light bulb does not really disintegrate slowly enough for us to see that it implodes rather than explodes;