By: Taj Elsir Hassan SulimanComputer Department2013MultimediaFundamental concepts in video
Video Concept Video is an excellent tool for delivering multimedia. Video places the highest performance demand on computer and itsmemory and storage. Digital video has replaced analog video as the method of choice formaking and delivering video for multimedia.
Video Concept Digital video device produces excellent finished products at afraction of the cost of analog. Digital video eliminates the image-degrading analog-to-digitalconversion. Many digital video sources exist, but getting the rights can bedifficult, time-consuming, and expensive.
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 ananalogue wave form or composite video.
Analogue Video Composite analogue video has all the video components: brightness, colour and synchronization Then combined into one signal for delivery Example : traditional television Problems: colour blending, low clarity, high generation lost, difficultto edit.DIGITAL ANALOGUE
Digitizing Video Digital video combines features of graphics and audio to createdynamic content for multimedia products. Video is simply moving pictures. Digitized video can be edited more easily. Digitized video files can be extremely large.
Digitizing Video Digital video is often used to capture content from movies and television to be usedin multimedia. A video source (video camera ,VCR, TV or videodisc) is connected to a video capturecard in a computer. As the video source is played, the analog signal is sent to the video card andconverted into a digital file (including sound from the video).VCRVideo Overlay Board /Video Capture CardPC
Analogue signal from VCRConverted to DIGITALby VIDEO CAPTURE CARDThe convertedsignal isentered inside acomputerSignal is processedVideo is editedusing video editingsoftware software
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 changingimages on a display device. Conversion from analogue to digital format requires the use on an ADC (Analogueto Digital Converter) A Digital to Analogue Converter (DAC) can be used to output digital video onanalogue equipment
Digital Video Video clip stored on any mass-storage device can be played back on a computer’smonitor without special hardware. Setting up a production environment for making digital video, requires somehardware specifications. Some specifications include computer with FireWire connection and cables, fastprocessor, plenty of RAM, fast and big hard disk.
File Size and Formats There is an important consideration: file size in digitized video which included1. frame rate2. image size3. color depth.File Size (bytes)= Frame Size(bytes) x FrameRate (fps) x Video Time(sec)
File Size and Formats1. Frame Rate animation is an illusion caused by the rapid display of stillimages. television and movies play at 30 fps but acceptable playbackcan be achieved with 15 fps.
File Size and Formats2. Image Size A standard full screen resolution is 640x480 pixels but to safe storingspace a video with 320x240 for a computer display is still acceptable. New high-definition televisions (HDTV) are capable of resolutions upto 1920×1080p60, 1920 pixels per scan line by 1080 scan lines, progressive, at 60frames per second.
File Size and Formats3. Color Depth The quality of video is dependent on the color quality (related to thenumber of colors) for each bitmap in the frame sequence.
3. Color Depth The color depth below 256 colors is poorer-quality image. The frame rate to below 15 fps causes a noticeable and distractingjerkiness that unacceptable. Changing the image size and compressing the file therefore becomeprimary ways of reducing file size.File Size and Formats24 bit 8 bit (256 colors)16 bit
A video clip is captured with a resolution of320 x 240, and using a color depth of 16bits, the frame rate is 25 fps , and the clip hasa duration of 29 seconds, calculate the filesize of the video clip?Solutions:Give : depth=16 bit (2 bytes), t=29 sec, framerate = 25 fpsExample:
Frame Size = Total no of pixels x Depth= 320 x 240 x 2 = 153,600 bytesFile size (bytes) = frame size x frame rate x t= 153600 x 25 x 29 = 111360000 bytesFile size (MB) = 111360000/1024 x 1024= 10.6 MBExample:
Video Compression The video compression/decompression programs are used so that video can fit on asingle CD and the speed of transferring video from a CD to the computer can beincreased. Let us say that a sequence of 25fps video is about 25MB. CD-ROM transfer rate is calculated as follows: 1X= 150KB per second 10X=1.5 MB per second 100X= 15 MB per second To overcome large video size, CODECS were developed.Compresseswhen savedCODECFile format usedsuch as: Avi,Mpeg, MovDecompresseswhen needed fordisplay
Video Compression Digital video compression schemes or codecs is the algorithm used to compress(code) a video for delivery. The codec then decodes the compressed video in real-time for fast playback. Streaming audio and video starts playback as soon as enough data has transferred tothe user’s computer to sustain this playback.FULLVIDEOTaken from the CDinto memory bufferDISPLAY ONSCREENMEMORY BUFFER
Video Compression Two types of COMPRESSION: Lossless compression. Preserves the exact image throughout the compression anddecompression process. E.g: text images is to identifyrepeating words and assign them a code.
Video Compression Two types of COMPRESSION: Lossy compression. Eliminates some of the data in the image and thereforeprovides greater compression ratios than losslesscompression. Applied to video because some drop in the quality is notnoticeable in moving images.
Video Compression Two types of CODEC (lossy): Spatial compression a digital compression of video data that compresses the size ofthe video file by compressing the image data of each frame Compression is done by removing redundancy from data inthe same frame.
Video Compression Two types of CODEC: Temporal compression a digital compression of video data that uses similarities ofsequential frames over time to determine and store only the imagedata that differs from frame to frame. Compression is done by removing similarity between successivevideo frames
Video Compression Flavors of file formats brand to choose: Microsoft’s AVI format QuickTime MPEG Div-X Wmv (Windows Media Video)
Video Compression Standards have been established for compressionprograms, including JPEG (Joint Photographic ExpertsGroup) and MPEG (Motion Picture Experts Group).
JPEG (Spatial) Often areas of an image (especially backgrounds) containsimilar information. JPEG compression identifies these area and stores them as blocksof pixels instead of pixel by pixel reducing the amount ofinformation needed to store the image. These program reduce the file size of graphic images byeliminating redundant information.
MPEG (Temporal) The changes in the image from frame to frame. Key frames are identified every few frames thechanges that occur from key frame. Provide greater compression ratios than JPEG. Initially, it requires extra hardware for multimedia.
Video Hardware and SoftwareVCRVideo Overlay Board /Video Capture CardVideo digitalEditing SoftwareMULTIMEDIA PC
Advantages of using Video Captures interest Increase retention Clarifies complex physical actions and relationships Can incorporate other media
Disadvantages of using Video Is expensive to produce Requires extensive memory and storage Requires special equipment Does not effectively illustrate abstract concepts andstatic situations
H.W A video clip with size of 45 MB is found in the face book,suppose your friend Taj is going to download it , and he isusing Zain Connect with bandwidth of 2 MB, calculatethe download time?
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