1.OVERVIEW Introduction to Video Analogue Video Digital Video2

2. INTRODUCTION TO VIDEO Moving pictures film and video: a series of still images presented at a speed that givesthe illusion of motion Film uses a photo emulsion that reacts to the differentwavelengths that reproduces images Analog film records images on transparent medium projected onto a screen Video uses electronic circuits to capture information Analog video records images as continuously varying electrical voltages that produce images on a CRT or projection screen Film and video rely on the trick of human eyes 3persistence of vision 3. INTRODUCTION TO VIDEO CONT What is video? A series of electronically captured still imagesdisplay in rapid succession to achieve the illusion ofmotion Two types of video: Analogue Digital Video vs. Animation? Recall topic 1.1 4 4. VIDEO SIGNAL Light = electromagnetic radiation The variation in light wavelength that representbrightness and colour can be rendered accuratelyby electronic circuit. Electronic waveforms signal = analogue signal Analogue video utilizes fluctuations in the electronicwaveform to represent brightness and colour. Analogue video signal continuous signal 5 5. VIDEO SIGNAL CONT To capture the electronic waves form digitally, wehave to represent them as finite binary numbers. The transformation from waveforms to numbers isnever always 100% correct. Digital representation of analog signal has to bebalanced between accuracy and functionality. 6 6. VIDEO FRAMES AND FRAME RATE Frame rate (Scan rate) how fast the frames aredisplayed. Standard frame rate: film = 24 fps 25 or 29.97 fps (depending on video standard) Lowering frame rate (e.g. 8 fps) can result in video withjerky movements or flickers. Generally, frame rate of 15 fps = natural movement; usefor Internet.What happens if weraise the framerate? 7 7. VIDEO RESOLUTION AND ASPECT RATIO Resolution = number of scan lines that fit on screen Aspect ratio = width divided by height 8 8. VIDEO IMAGE Video image is created by an electron gun in theCRT. The electronic signal illuminates lines ofphosphorus dots on the screen. Methods to illuminate or scan the image: Interlaced scan alternates the scanning between oddnumbered lines in the frame and even numbered lines inthe frame (NTSC). Progressive scan scans each line of the imagesequentially (computer monitor). 9 9. VIDEO COLOUR SIGNALSComposite VideoComponent Video Combines two signals: Colors are represented Luminance or amountseparately.of brightness in the Red, Green, Blue lightimage. signals combine to Chrominance or color create color range.hue in the image. Better color quality. Inexpensive to createand transmit. Video captured in component color. NTSC standard = composite color. 10 Computer monitors = component color. 10. ANALOGUE VIDEO11 11. ANALOGUE VIDEO Analogue video consist of series of imagesproduced by continuous analogue signals.Ref: http://www.danalee.ca/ttt/analog_video.htm12 12. ANALOGUE VIDEO In an analogue video signal, each frame isrepresented by a fluctuating voltage signal. This is known as analogue waveform. Composite analogue video has all its components(brightness, colour, synchronisation information, etc.)combined into one signal.13 13. ANALOGUE VIDEO FORMATS & STANDARDS A broadcast television standard: NTSC - National Television Standards Committee Developed in the US and first used in 1954 The oldest existing broadcast standard. Consists of 525 horizontal lines of display and 60 vertical lines. Scanning method (interlacing) Only one type exists - NTSC M. PAL - Phase Alternating Line Developed in Germany and first used in 1967.A variant of NTSC, PAL uses a 625/50-line display. Different types use different video bandwidth and audio carrierspecifications. Common types are B, G, and H. (Less common - D, I, K, N, & M) These different types are generally not compatible with one another. In England and much of Europe14 14. ANALOGUE VIDEO FORMATS & STANDARDS CONT SECAM - Systme lectronique pour Couleur avec Mmoire. Developed in France and first used in 1967. Uses a 625/50 line display. Different types use different video bandwidth and audio carrier specifications. Types B and D are usually used for VHF. Types G, H, and K are used for UHF. Types I, N, M, K1 and L are used for both VHF and UHF. These different types are generally not compatible with oneanother. Whats the TV standard in Malaysia?15 http://countrycode.org/tv-standards 15. DIGITAL VIDEO16 16. DIGITAL VIDEO Digital video uses binary numbers to representimage data Two sources of digital video: Convert existing analog video to digital. Create or purchase digital footage. 17 17. ANALOGUE VS. DIGITALAnalogue VideoDigital Video Continuous signal Digital or discrete-timefluctuating voltage signal in binarysignalnumber Reduces in quality over Stable/enduring qualitythe time or when Random accessduplicates Linear access 18 18. DIGITAL VIDEO QUALITY Factors contribute to quality Screen resolution Number of horizontal and vertical pixels used to present the video image. Colour resolution the number of colours displayed on the screen at one time. Frame rate - Number of individual video framesdisplayed per second. The higher the frame rate, the smoother the video Compression method Algorithm used to compress and decompress the video.Developers can adjust these factors to optimize delivery of digital video. 19 19. SCREEN RESOLUTION Screen resolution (or output resolution) - number ofhorizontal and vertical pixels used to present thevideo image. impacts processing, storage, and transmissionrequirements. High quality digital video (DV) format is 720 X 480 (or350,000 pixels at rates of 30fps). CD-Rom and Internet are too slow to deliver that muchdata. Solution: reduce the display size, which reduces thenumber of pixels/second to output. Why does thevideo degradeWhy is YouTubewhen viewed at fullvideos are best atscreen? 20smaller size? 20. DIGITAL VIDEO - COMPRESSION Compression is key to successful delivery of digitalvideo. Three strategies for compressing video: Intra-frame: re-encodes within the frame. Inter-frame: eliminates intervening frames saving onlychanges between the frames. Variable bit rate (VBR) CBR (constant bit rate) assigns same number of bits persecond to all parts of the video. VBR assigns more bits to complex scenes and fewer bits tosimpler scenes.21 21. DIGITAL VIDEO COMPRESSION Choosing compression depends on: Output destination DVD Internet Editing capability Detailed editing tasks Limited editing tasks Type of images in video Complex scenes Similar scenes 22 22. INTRA-FRAME Lossless strategy could be Run-length encoding(RLE). Result: smaller more efficient file with all the originaldata. Lossy strategy commonly used is M-JPEG. Individual images are compressed and linked togetheras motion sequences. Best for video editing as every frame is preserveddespite data being lost from each separate frame.23 23. INTER-FRAME MPEG compression identifies: I-frames: "intra-frame" or complete compressedframes P-frames: predictive frames record moresignificant changes. B-frames: bidirectional frames record smallerchanges between the I and P frame. Good choice for distributing video. Not appropriate for recording and editing video 24 24. VARIABLE BIT RATE Constant Bit Rate encoding uses same number ofbits per second for simple and complex video. Variable Bit Rate assigns more bits to complexscenes and fewer bits to simpler scenes. Common option in video editing software. 25 25. COMMON VIDEO CODECS MPEG MPEG-1 (short videos on Video CDoptical discformat). MPEG-2 (transmission of video for television). MPEG-4 (video over the web). M-JPEG (less-compressed higher quality fileswithout inter-frame loss) RealVideo (proprietary codec for streaming videoon web) DV (uses M-JPEG, suitable for authoring or 26archiving) 26. DIGITAL VIDEO - FORMATS & STANDARDS Developers use these Common video fileformats to render the finalformatsproject in a form suitable for Windows Video file (.avi)delivery D1 Movie file (.mpg or .mpeg) D2 and D3 Windows Media Video file (.mwv) DV CD Video MPEG-4 file (.mp4) DVD video QuickTime Movie file Quicktime (.mov, .qt) Video for Windows Any others? Real Video.27 27. DIGITAL VIDEO CHALLENGES Large file sizes Every second of uncompressed digital video requires30MB of storage. Hardware performance Computer processors, memory and bus size must deliverdigital video to the screen at full motion frame rates. Distribution methods DVD players. High speed network bandwidth Digital video made possible by: Compression algorithms Fast computer hardware DVD storage Gigabit bandwidth. 28 28. DIGITAL VIDEO Quality is long lasting Quality for duplicates is almost the same as theoriginal Allow random search/access of content Can be compressed for better and easier storage anddistribution29 29. MORE ON VIDEO..Things to consider: When to use When video can say something that would beimpossible or difficult to say with medium such asgraphics, photos, or text. Where to place In the page In a separate context User Interaction with Video No control video play immediately User control play/stop buttons 30 30. USES OF VIDEO Consumer use Corporate Use Television Corporate video Home entertainment Live video / video on Etc.. ?demand Video surveillance system 31 31. SUMMARY Introduced video definition and concept Two categories of video Ref and Readings: https://learningnetwork.cisco.com/docs/DOC-6492 http://www.danalee.ca/ttt/analog_video.htm Barfield, L. (2004). Design for New Media: Interactiondesign for multimedia and the web. Essex, England:PearsonAddison Wesley. 32