Introduction to Multimedia

1. Introduction to Multimedia VIDEO

2. 6.1 Video Concept • Video is an excellent tool for delivering multimedia. • Video places the highest performance demand on computer and its memory and storage. • Digital video has replaced analog video as the method of choice for making and delivering video for multimedia.

3. 6.1 Video Concept • Digital video device produces excellent finished products at a fraction of the cost of analog. • Digital video eliminates the image-degrading analog-to-digital conversion. • Many digital video sources exist, but getting the rights can be difficult, time-consuming, and expensive.

4. 6.2 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.

5. 6.2 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, difficult to edit. DIGITAL ANALOGUE

6. Digitizing Video • Digital video combines features of graphics and audio to create dynamic content for multimedia products. • Video is simply moving pictures. • Digitized video can be edited more easily. • Digitized video files can be extremely large.

7. VCR Digitizing Video • Digital video is often used to capture content from movies and television to be used in multimedia. • A video source (video camera ,VCR, TV or videodisc) is connected to a video capture card in 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). Video Overlay Board / Video Capture Card • PC

8. Analogue signal from VCR Converted to DIGITAL by VIDEO CAPTURE CARD The converted signal is entered inside a computer Signal is processed Video is edited using video editing software software

9. 6.3 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

10. 6.3 Digital Video • Video clip stored on any mass-storage device can be played back on a computer’s monitor without special hardware. • Setting up a production environment for making digital video, requires some hardware specifications. • Some specifications include computer with FireWire connection and cables, fast processor, plenty of RAM, fast and big hard disk.

11. File Size and Formats • There is an important consideration: • file size in digitized video which included • frame rate • image size • color depth.

12. File Size and Formats • Frame Rate • animation is an illusion caused by the rapid display of still images. • television and movies play at 30 fps but acceptable playback can be achieved with 15 fps.

13. File Size and Formats • Image Size • A standard full screen resolution is 640x480 pixels but to safe storing space a video with 320x240 for a computer display is still acceptable. • New high-definition televisions (HDTV) are capable of resolutions up to 1920×1080p60, • 1920 pixels per scan line by 1080 scan lines, progressive, at 60 frames per second.

14. File Size and Formats • Color Depth • The quality of video is dependent on the color quality (related to the number of colors) for each bitmap in the frame sequence.

15. File Size and Formats • Color Depth • The color depth below 256 colors is poorer-quality image. • The frame rate to below 15 fps causes a noticeable and distracting jerkiness that unacceptable. • Changing the image size and compressing the file therefore become primary ways of reducing file size. 24 bit 16 bit 8 bit (256 colors)

16. Video Editing Terminology • Linear • It plays end to end in one direction, usually pertains to videotape editing specifically the editing of linear tape segments into one final master tape.

17. Video Editing Terminology • Non-linear • Refers to the editing of disk-based digital video. • The software provides an on screen map of what the final video sequences should look like incorporating the edits, splices, special effects, transitions and sound tracks.

18. Special Effects • Transitions • Such as fading, wiping, splatters, scrolling, stipple and many more are available by simply dragging and dropping that transition between the two video clips.

19. Special Effects • Superimposing • The ability to superimpose one clip over another is a valuable technique. • The technique of green screening is identical except that the color green is used for the screen and later digitally removed. • The blue screen and green screen superimposing are just two of the superimposing technique available.

20. Special Effects • Superimposing • Digital video editing applications provide special effect filters to create lens flares and emboss, tint, pan, twist and zoom the video image. • These special effects can often be set up to change over the duration of the video clip.

21. Compresses when saved CODEC File format used such as: Avi, Mpeg, Mov Decompresses when needed for display 6.4 Video Compression • The video compression/decompression programs are used so that video can fit on a single CD and the speed of transferring video from a CD to the computer can be increased. • 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 secondt • To overcome large video size, CODECS were developed.

22. FULL VIDEO Taken from the CD into memory buffer DISPLAY ON SCREEN MEMORY BUFFER 6.4 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 to the user’s computer to sustain this playback.

23. 6.4 Video Compression • Two types of COMPRESSION: • Lossless compression. • Preserves the exact image throughout the compression and decompression process. E.g: text images is to identify repeating words and assign them a code.

24. 6.4 Video Compression • Two types of COMPRESSION: • Lossy compression. • Eliminates some of the data in the image and therefore provides greater compression ratios than lossless compression. • Applied to video because some drop in the quality is not noticeable in moving images.

25. 6.4 Video Compression • Two types of CODEC (lossy): • Spatial compression • a digital compression of video data that compresses the size of the video file by compressing the image data of each frame • Compression is done by removing redundancy from data in the same frame.

26. 6.4 Video Compression • Two types of CODEC: • Temporal compression • a digital compression of video data that uses similarities of sequential frames over time to determine and store only the image data that differs from frame to frame. • Compression is done by removing similarity between successive video frames

27. 6.4 Video Compression • Flavors of file formats brand to choose: • Microsoft’s AVI format • QuickTime • MPEG • Div-X • Wmv (Windows Media Video)

28. 6.4 Video Compression • Standards have been established for compression programs, including JPEG (Joint Photographic Experts Group) and MPEG (Motion Picture Experts Group).

29. JPEG (Spatial) • Often areas of an image (especially backgrounds) contain similar information. • JPEG compression identifies these area and stores them as blocks of pixels instead of pixel by pixel reducing the amount of information needed to store the image. • These program reduce the file size of graphic images by eliminating redundant information.

30. MPEG (Temporal) • The changes in the image from frame to frame. • Key frames are identified every few frames the changes that occur from key frame. • Provide greater compression ratios than JPEG. • Initially, it requires extra hardware for multimedia.

31. VCR Video Hardware and Software MULTIMEDIA PC Video Overlay Board / Video Capture Card Video digital Editing Software

32. Video Editing Software • Incorporating transitions such as dissolves, wipes and spin. • Superimposing titles and animating them, such as fly-in logo. • Applying special effects to various images, such as twisting, zooming, rotating and distorting. • Synchronizing sound with the video. • Apply filters that control color balance, brightness & contrast, blurring, distortions and morphing.

33. Advantages of using Video • Captures interest • Increase retention • Clarifies complex physical actions and relationships • Can incorporate other media

34. Disadvantages of using Video • Is expensive to produce • Requires extensive memory and storage • Requires special equipment • Does not effectively illustrate abstract concepts and static situations

35. Summary • Digital video method is used for making and delivering video for multimedia. • Compression techniques help to reduce the file sizes to more manageable levels • Two types of compression lossless and lossy. • Standards for compression program are JPEG and MPEG.