1. MULTIMEDIA TECHNOLOGY AND APPLICATIONS CHAPTER 5. INTRODUCTION TO VIDEO

2. 5.1 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. 5.1 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. 5.2 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. 5.2 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. 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).
VCR
Video Overlay Board /
Video Capture Card PC

8. The converted signal is entered inside a computer
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. 5.3 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. File Size and Formats There is an important consideration:
file size in digitized video which included
frame rate
image size
color depth.

11. 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.

12. 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.

13. 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.

14. File Size and Formats Color Depth 24 bit 16 bit 8 bit (256 colors)
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)

15. 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.

16. 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.

17. 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.

18. Decompresses when needed for display
5.4 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.
Compresses when saved
CODEC
File format used such as: Avi, Mpeg, Mov
Decompresses when needed for display

19. 5.4 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.
FULL VIDEO
Taken from the CD into memory buffer
DISPLAY ON SCREEN
MEMORY BUFFER

20. 5.4 Video Compression Flavors of file formats brand to choose:
Microsoft’s AVI format
QuickTime
MPEG
Div-X
Wmv (Windows Media Video)

21. 5.4 Video Compression
Standards have been established for compression programs, including JPEG (Joint Photographic Experts Group) and MPEG (Motion Picture Experts Group).

22. 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.

23. 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.

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

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

26. 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

27. 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.

28. Analog Video
Represented as a continuous (time varying) signal

29. Analog Video
From T1

30. NTSC (National Television System Committee)
It uses the familiar 4:3 aspect ratio (i.e., the ratio of picture width to its height)
Uses 525 scan lines per frame at 30 frames per second (fps).
NTSC follows the interlaced scanning system, and each frame is divided into two fields, with lines/field.
Thus the horizontal sweep frequency is 525x =15,734 lines/sec, so that each line is swept out in 63.6 µ sec (1/ x 103 sec )
63.6 µ sec = 10.9 µ sec for Horizontal retrace µ sec active line signal
For the active line signal during which image data is displayed

31. NTSC (National Television System Committee) [3]
NTSC video is an analog signal with no fixed horizontal resolution
Pixel clock is used to divide each horizontal line of video into samples. Different video formats provide different numbers of samples per line
Uses YIQ Color Model

32. PAL (Phase Alternating Line)
Widely used in Western Europe, China, India, and many other parts of the world.
Uses 625 scan lines per frame, at 25 frames/second, with a 4:3 aspect ratio and interlaced fields
Uses the YUV color model
Uses an 8 MHz channel and allocates a bandwidth of 5.5 MHz to Y, and 1.8 MHz each to U and V.

33. Digital Video Advantages over analog:
Direct random access --> good for nonlinear video editing
No problem for repeated recording
No need for blanking and sync pulse
Almost all digital video uses component video

34. High Definition TV (HDTV)
The main thrust of HDTV (High Definition TV) is not to increase the definition in each unit area, but rather to increase the visual field especially in its width.
The first generation of HDTV was based on an analog technology developed by Sony and NHK in Japan in the late 1970s.
Uncompressed HDTV will demand more than 20 MHz bandwidth, which will not fit in the current 6 MHz or 8 MHz channels
More than one channels even after compression.

35. High Definition TV (HDTV)
The salient difference between conventional TV and HDTV:
HDTV has a much wider aspect ratio of 16:9 instead of 4:3.
HDTV moves toward progressive (non-interlaced) scan. The rationale is that interlacing introduces serrated edges to moving objects and flickers along horizontal edges.

37. ©Some of the pictures and text are from internet online free resource and wikipedia