Video

Learning Outcomes Pada akhir pertemuan ini, diharapkan mahasiswa akan mampu : Menunjukkan Penggunaan Video pada Aplikasi Multimedia

Outline Materi Different Kind of Movies Analogue Video Digital Video Compression Technique Broadcast Video Standards Digital Video Format Using Digital Video

Different Kind of Movies Movies from Film Analog Video Digital Video

Movie From Film Sequential image frames are recorded on film using a light sensitive technology similar to still photography. Film must be chemically developed Editing requires physically cutting and splicing the film

Analogue video Video information that is stored using television video signals, film, videotape or other non-computer media Each frame is represented by a fluctuating voltage signal known as an analogue wave form or composite video. Composite analogue video has all the video components: brightness, colour and synchronization Then, combined into one signal for delivery Usage : television Problems: colour blending, low clarity, high generation lost, difficult to edit

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 ADC (Analogue to Digital Converter) A Digital to Analogue Converter (DAC) can be used to output digital video on analogue equipment

File Size Considerations Several elements determine the file size, in additional to the length of the video. These including: Frame rate Number of images displayed within a specified amount of time to convey a sense of motion Usually measured in frames per second Standard video movie  30 fps, movie film  24 fps Video digital  at least 15 fps Frame or Image size 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 Standard full screen resolution is 640x480 pixels Video screen display is one fourth the size of the full window screen (320x240) Color depth/Resolution Number of colors displayed on the screen at one time Ranging from 1 bit to 8 bit, 16 or 24 bit per pixel

File Size Considerations Quality directly related to frame size, image size and color depth. Quality also depends on content. Motion picture needs higher frame rate File size = Frame Size x Frame Rate x Color Depth x Time Where: Frame size = image size ( width x height in pixels) Frame rate = frames per second Color depth = measured in bytes Time = time in seconds This does not include any sound data !

Compression techniques Since the size of raw digital video is so prohibitively large we need some means to compress the information Video compression and decompression program, known as Codecs 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 Lossless compression techniques do not lose information throughout the compression and decompression process Example use in text images Exactly same before and after compression Technique is identify repeating words and assign them a code. Decompression, the code would be changed back to the actual word.

Digital video editing Analogue tape editing is a linear process To find the section you want, you may have to forward or rewind the video tape To move a section to another place in the sequence you have to either re-record the section onto another tape or physically cut and splice the video tape Digital video editing can be non-linear process You can move sections around inside the computer and play those sections back in any order

Broadcast Video Standards NTSC North America, South America, Japan 525 interlaced resolution lines 30 frames per second (fps) PAL (Phase Alternate Line) Australia, South Africa, Europe 625 interlaced resolution lines 25 frames per second (fps) SECAM France, Russia 625 interlaced resolution lines 25 frames per second (fps) HDTV Six different formats Aspect ratio is 16:9

Overscan

Digital Video File Formats .MOV signifies Quicktime, an Apple standard. It is playable on Macintosh and Windows machines. .AVI is a Microsoft standard that is playable on Windows and Macintosh machines. .MPEG (.MPG) is playable on Unix and Windows machines. Macintoshes can play MPEG, but may have trouble with the audio track. .RM files are used by RealNetworks streaming. They are playable on Windows, MacOS, and Unix computers. .ASF files are a Microsoft streaming format, and play on Windows, MacOS, and Solaris. .WMV files are a Microsoft format used in Microsoft MovieMaker

MPEG video Named after the Moving Picture Experts Group who devised the compression and file formats There are a number of MPEG formats: MPEG-2 is used for digital TV broadcasts and DVDs MPEG-1 is a format used for low quality video (generally displayed on computers) MPEG-1 Layer 3 is the popular encoding mechanism for MP3 audio files (more on this later in this course) MPEG-4 is a new format for multimedia presentations Can require separate hardware to decode higher quality MPEG video data

MPEG compression example A simple scene showing a car moving across a desert landscape Only the difference between the current and next frame needs to be stored This is called intraframe coding

QuickTime Developed by Apple, Inc. Primarily for playback without any hardware assistance Can achieve compression ratios of 25 to 200:1 The QuickTime format can also store audio, graphics, 3D and text making it more much versatile for multimedia applications

Microsoft AVI Audio Video Interleave format Interleaving is a technique used to embed two or more things into the same stream of information In every chunk of information you will find some video data and some audio data 001001010010010101010011110101... ... 8, 16 or 24 bits Video information Audio information 001001010010010101010011110101...

Consumer desktop video Typified by the Apple iMac DV computer IEEE 1394 or FireWire interface Digital camcorders

How Video can be used effectively Showing physical procedures. Some uses are: Installing a board in a PC Adjusting engine timing Attracting and holding attention. Some uses are: Advertising products and services Teaching new skills to busy employees Presenting scenarios. Some uses are: Training technicians to respond to equipment malfunctions Demonstrating possible uses for a product Analyzing motion . Some uses are: Body motion to improve athletic performance Traffic patterns for transportation planning

Advantages and Disadvantages of using video Carefully planned, well-executed video clips can make a dramatic difference in a multimedia project Use video only when all other methods (text, still images) are not enough; don’t use it just because it’s possible Video adds visual impact to multimedia applications: Advantages Captures interest Increase retention Clarifies complex physical actions and relationships Can incorporate other media Disadvantages Is expensive to produce Requires extensive memory and storage Requires special equipment Does not effectively illustrate abstract concepts and static situations