Video Analog Vs Digital

http://cbdd.wsu.edu/kewlcontent/cdoutput/TR502/page8.htm

Video combines pictures and sounds displayed over time. Video (as opposed to animation) starts with a continuous event and breaks it up into frames, whereas an animation starts with frames.

Video Formats Video formats are made up of:

• the container• the codec(s) used inside that container.

The container describes the structure of the file: where the various pieces are stored, how they are interleaved, and which codecs are used by which pieces.  It may specify an audio codec as well as video.

A codec ("coder/decoder") is a way of compressing the file to decrease file size, while maintaining quality

Examples Video Formats (Containers)

• AVI (.avi)• Quicktime• WMV (.wmv)

Video Codecs • MPEG(Moving Pictures Expert Group)• RM (Real Media)• DivX

Comparison of CodecsCodec Quality Speed Comment

MPEG 4

Div X

RM

Video Processing Analog signals (pictures and audio)

are converted to digital signals via a video capture card

A video or animation is made up of frames: individual pictures that are put together to create the illusion of movement.

Video Video files are very large, which is an

important factor in deciding what hardware to use to store the video files.

Speed is an issue in video and animation…the frame rate is the number of frames per second that are shown

Higher frame rate = higher quality, smoother video= more file size needed

Frame ratesFrames per second

Examples

30 Screen refresh rate of monitors

24 Film speed for motion pictures

12 Cartoon animation speed

8 Minimum speed for the illusion of motion

Calculations File size in Kb of a 30 minute

Simpson’s episode at 24 frames per second.

How many frames are there?

Number of frames=frame rate x time in seconds

File size of each frame Each frame is 2048 by 872 pixels and

a bit depth of 8

File Size for the episode Number of frames x File size of each

frame

Why is this important? BECAUSE file size will effect the

requirements of a system for primary and secondary storage

Higher file size = greater storage requirements

Higher file size = greater primary memory requirements (bigger, faster computer)

Video – File Types MPEG (The Moving Picture Experts Group)

The MPEG standards consist of different Parts. Each part covers a certain aspect of the whole specification. MPEG has standardized the following compression formats and ancillary standards:

Video – File Types AVI

Audio Video Interleave, is a multimedia container format introduced by Microsoft in November 1992 as part of its Video for Windows technology. AVI files can contain both audio and video data in a file container that allows synchronous audio-with-video playback. Like the DVD video format, AVI files support multiple streaming audio and video, although these features are seldom used.

Video – File Types MP4

MPEG-4 (1998): Coding of audio-visual objects. MPEG-4 uses further coding tools with additional complexity to achieve higher compression factors than MPEG-2. In addition to more efficient coding of video, MPEG-4 moves closer to computer graphics applications. In more complex profiles, the MPEG-4 decoder effectively becomes a rendering processor and the compressed bitstream describes three-dimensional shapes and surface texture. MPEG-4 also provides Intellectual Property Management and Protection (IPMP) which provides the facility to use proprietary technologies to manage and protect content like digital rights management.

MPEG-4 is a multimedia container format. It is most commonly used to store digital video and digital audio streams, especially those defined by MPEG, but can also be used to store other data such as subtitles and still images. Like most modern container formats, MPEG-4 Part 14 allows streaming over the Internet.

Video video editing: import/export transitions Titles

special effects, eg: twisting zooming rotating slow motion time lapse distorting synchronising sound

filters: colour balance brightness contrast blurring morphing

This will be done in class with video software