Chapter 6 Multimedia

Three analog video standards:

- Composite Video - Separate Video (S-Video) - Component Video

Factors that Determine Digital Video Quality

- Frame Rate - Image Size - Colour Depth

Category of Video Compression

- Lossless: Video files that are compressed but doesn't lose any quality to the file (MPEG-4 AVC H.264). - Lossy: Video files that lose some quality when its being compressed (.mkv, .flv, .mp4...).

Calculate Video File Size

Video File Size = Frame Size (W x H in pixel) x Frame Rate (fps) x Colour Depth (byte) x Duration (second)

What is a container?

• A container is a collection of files that stores information about the digital file. • It consists of video data in a video coding format (e.g. VP9) alongside audio data in an audio coding format (Opus). • It can also contain synchronization information, subtitles, and metadata such as the title.

Frame Rate

• A number of images displayed within a specified amount of time to convey a sense of motion. - Animation is an illusion caused by the rapid display of still images. • Usually measured in frames per second (fps).

Digital Video File Format

• A video file normally consists of a container. • A video file's format determines: - Which programs can open and play it. - How much space it occupies on a disk. - How fast it travels over an Internet connection. • Most video file format support lossy compression.

Component Video

• A video signal that has been split into two or more component channels. • In popular use, it refers to a type of component analog video (CAV) information that is transmitted or stored as three separate signals.

Analogue Video

• Analog video is a video signal transferred by an analog signal. • An analog color video signal contains luminance (Y) and chrominance (C) of an analog television image. • In an analog system, the output of the CCD is processed by the camera into three channels of color information (RGB), synchronization pulses (sync) and signals are recorded onto a magnetic tape.

Form of Video Signal

• Analog video is essentially a product of the television industry and therefore conforms to television standards. • Digital video is a product of the computing industry and therefore conforms to digital data standards. • Digital video has replaced analog video as the method of choice for making and delivering video for multimedia.

Video Compression

• Because of the large sizes associated with video files, video compression/decompression programs, known as CODECS, have been developed. • These programs can substantially reduce the size of video files, which means that more video can fit on a single CD and that the speed of transferring video from a CD to a computer can be increased.

Composite Video

• Composite video produces the lowest quality video and is most susceptible to generation loss. • Generation loss is the loss of quality that occurs while moving from original footage to editing master to copy. • A video signal that combines the luminance and chrominance, and sync (horizontal and vertical synchronizing signals) into a single waveform carried on a single wire pair.

Digital Video

• Digital video is the digitisation of analogue video signals into numerical format • It creates the illusion of full motion by displaying a rapid sequence of changing images on a display device. • Conversion from analogue to digital format requires the use on an Analogue to Digital Converter (ADC) • A Digital to Analogue Converter (DAC) can be used to output digital video on analogue equipment

Separated Video (S-Video)

• It has a lower color resolution than component video. • A video signal that separated the luminance (Y) and chrominance (C) on two separate tracks to improve the picture quality. - Y is the luma signal, which carries the luminance - or black-and-white - of the picture, including sync (horizontal and vertical synchronizing signals). - C is the chroma signal, which carries the chrominance or coloring-in - of the picture. This signal contains both the saturation and the hue of the video.

Digitizing the Video Signal

• It is usually recorded and played as an analog signal. • It must, therefore, be digitized in order to be incorporated into a multimedia title. • A video source (video camera, VCR, TV or videodisc) is connected to a video capture card on a computer. • As the video source is played, the analog signal is sent to the video card and converted into a digital file (including sound from the video).

How Video Works and Is Displayed

• Light reflected from an object through the camera's lens is converted into an electronic signal by a special sensor called a charge-coupled device (CCD). • This electronic signal contains three channels of color (RGB) information and synchronization pulses (sync).

Lossless Compression

• Lossless compression techniques do not lose information throughout the compression and decompression process - Example use in-text images - Exactly same before and after compression - The technique is to identify repeating words and assign them a code. - Decompression, the code would be changed back to the actual word.

Lossy Compression

• Lossy compression techniques cause some information to be lost from the original image - Redundant information - Example: Image and video - JPEG and MPEG - Intraframe and Interframe

Advantages of Digital Video

• One of the advantages of digitized video is that it can be easily edited. (noise removal, cut, and paste, .etc) • The video is stored as a standard computer file. • Software motion video does not require specialized hardware for playback. • Digital video requires neither a video board in the computer nor an external device (which adds extra costs and complexity) such as a video disc player. • Direct access is possible, which makes non-linear video editing achievable as a simple, rather than a complex, task. • Repeated recording does not degrade image quality • Long-lasting.

Disadvantages of Digital Video

• Requires large storage capacity devices. • Copies can be made illegally. • Need a fast computer system for playback and capture. • Requires knowledge of digital compression technology.

Introduction to Video

• The recording, reproducing, or broadcasting of moving visual images. • Video is very hardware-intensive (require the highest performance demand on your computer) • Storage issue: full-screen, uncompressed video uses over 20 megabytes per second (MBps) of bandwidth and storage space. • Processor capability in handling very huge data on real-time delivery

Image Size / Resolution

• The width and height of each individual frame or image. • Determines the quality of the image displayed and the processing involved to display that image.

Analogue Video Standards

• There are several video standards for managing analog CCD output, each dealing with the amount of separation between the components. - the more separation of the color information, the higher the quality of the image (and the more expensive the equipment).

Multimedia Video

• Video is an excellent tool for delivering multimedia. - The advantage of integrating video into a multimedia presentation is the capacity to effectively convey a great deal of information in the least amount of time. • Video makes use of all of the elements of multimedia, bringing your products and services alive but at a high cost.

Definition of Video

• Video is the technology of electronically capturing, recording, processing, storing, transmitting, and reconstructing a sequence of still images representing scenes in motion.

Uses of Video in Multimedia

• Video simulations show procedures and interactions that would be dangerous to perform unprofessionally • Games use video to simulate flight, car racing, and other action • Used as reference material in Web sites and CD-ROMs • Video conferences enable participants to see each other and witness demonstrations