Digital Video Theory

Three characteristics of digital video

The three main characteristics are: proportionality, bit rate and resolution.

proportionality: is the reason between the height and width of the image.

bit rate: indicates the amount of information bits that are transmitted in the video

resolution: the amount of pixels in width and height of the capture.

Difference between codec and file format

CODEC: is made of 2 components COder (i.e. Encoder) – DECoder. Essentially, this signifies the encoding of the signal at the transmission end and corresponding inverse operation i.e. decoding at the receiving end.

File Format: Is a specification that describes how the content is stored or encapsulated prior to transmission over a channel. In some cases, file format is used interchangeably with some of the real-time encapsulation protocols which are used for streaming content.

Main types of video files

The main ones are: AVI (Audio Video Interleave), FLV (Flash Video Format), WMV (Windows Media Video), MOV (Apple QuickTime Movie), MP4 (Moving Pictures Expert Group 4).

AVI: Developed by Microsoft and introduced to the public in November 1992 as part of its Video for Windows technology, the AVI format is one of the oldest video formats.

FLV: it has become the most common online video viewing platform used on the Web today. As almost all video sharing sites such as Youtube stream videos in Flash, practically all browsers support and are compatible with the Flash Video format and can play the video with ease.

WMV: WMV files are the tiniest video files over the Web, as their file size decreases significantly after compression, which results in poor video quality. However, one advantage of this small file size is that it is probably the only video file format that allows users to upload and share their videos through the e-mail system.

MOV: popular type of video sharing and viewing format amongst Macintosh users, and is often used on the Web, and for saving movie and video files.

MP4: standard developed by the Motion Pictures Expert Group who was responsible for setting industry standards regarding digital audio and video, and is commonly used for sharing video files on the Web.

Main video resolution

There are two types of video resolution: Standard Definition (SD) and High Definition (HD). The most popular standard resolutions are 640×360 and 640×480 for video, and 720×480 and 720×576 for DVD.