This document discusses digital video techniques for multimedia, including video digitizing, compression standards like JPEG and MPEG, file formats, editing and special effects. Digital video has replaced analog as it produces high quality output at low cost without quality degradation from conversions. Proper compression is needed to optimize file sizes for delivery mediums like CD-ROM.

1. Chapter 7-Video

2. Objectives
 Consider the implications of using digital video in multimedia.
 Discuss video recording and how it relates to multimedia
production.
 Prepare digital video and images for conversion to television.
 Prepare for shooting and editing video for use in multimedia.
 Select the best video recording formats for your multimedia
project.
 Begin preparing video for the Web and CD-ROM.

3. Overview
 Concept of video
 How video works?
 Analog video
 Digital video
 Video digitizing
 Shooting and editing video
 Optimizing video files for CD-ROM
 Broadcast video standards

4. Concept of Video
 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 as the method of choice
for making and delivering video for multimedia.

5. Concept of Video
 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.

6. How Video Works
 Light reflected from an object through the camera’s lens is
converted into electronic signal by charge-coupled device
(CCD).
 This electronic signal contains three channels of color
information and synchronization pulses (sync).
 Several video standards exist that deal with the amount of
separation between the components of the signal.

7. Analog 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.

8. Analog 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

9. Analog Video
Video color:
 Television sets use composite input. Hence colors are
less pure and less accurate than computers using RGB
component.
 NTSC television uses a limited color palette and
restricted luminance (brightness) levels and black levels.
 Some colors generated by a computer that display fine
on a RGB monitor may be illegal for display on a NTSC
TV.
 While producing a multimedia project, consider whether
it will be played on a RGB monitor or a conventional
television set.

10. Analog Video
Interlacing effects:
 In television, the electron beam makes two passes on the
screen while drawing a single video frame.
 It first lays down all the odd-numbered lines, and then all the
even-numbered lines, hence they are interlaced.
 While capturing images from a video signal, they can be
filtered through a de-interlacing filter provided by image-
editing applications.

11. Analog Video
Text and titles for television and taking care of analog tapes:
 Titles for video productions can be created with an analog
character generator.
 Computers can create titles digitally using video and image-
editing software.
 New tapes should always be fast-forwarded to the end and
then rewound, to ensure even tape tension.

12. 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

13. 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.

14. Video Digitizing
 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

15. 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
Video Digitizing

16. Digital Video Architecture
 Digital video architecture consists of a format for encoding
and playing back video files by a computer.
 Architecture includes a player that can recognize and play
files created for that format.

17. Digital 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

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

19. Digital 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.

20. Digital Video 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.

21. Digital 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.

22. Digital Video Compression
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

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

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

25. 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.

26. 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.

27. MPEG (Temporal)
 MPEG is a real-time video compression algorithm.
 MPEG-4 includes numerous multimedia capabilities and is a
preferred standard.
 MPEG-7 (or Multimedia Content Description Interface)
integrates information about motion video elements with
their use.

28. File Size and Formats
 There is an important consideration:
 file size in digitized video which included
1. frame rate
2. image size
3. color depth.

29. File Size and Formats
1. 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.

30. File Size and Formats
2. 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.

31. File Size and Formats
3. 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.

32.  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.
File Size and Formats
24 bit 8 bit (256 colors)
16 bit

33. Optimizing Video Files for CD-
ROM
 CD-ROMs provide an excellent distribution medium for
computer-based video.
 When preparing video for CD-ROM distribution, interleave
the audio track(s) with the video track.
 Key frames should be used every 10 to 15 frames and the
size of the video window must be kept small.
 The Sorenson codec is optimized for CD-ROM playback.

34. Broadcast Video Standards
National Television Standards Committee (NTSC):
 These standards define a method for encoding information into
electronic signal that creates a television picture.
 It has screen resolution of 525 horizontal scan lines and a scan
rate of 30 frames per second.

35. Broadcast Video Standards
Phase Alternate Line (PAL) and Sequential Color and
Memory (SECAM):
 PAL has a screen resolution of 625 horizontal lines and a
scan rate of 25 frames per second.
 SECAM has a screen resolution of 625 horizontal lines and
is a 50 Hz system.
 SECAM differs from NTSC and PAL color systems in its
basic technology and broadcast method.

36. Broadcast Video Standards
Advanced Television Systems Committee (ATSC) Digital
Television (DTV):
 This digital standard provides TV stations with sufficient
bandwidth to present four or five Standard Television (STV)
signals or one High Definition TV (HDTV) signal.
 This standard allows for transmission of data to computers
and for new Advanced TV (ATV) interactive services.

37. Shooting and Editing Video
 Import video and sound at the highest resolution and with
the least amount of compression possible.
 Resolution should be reduced and footage must be
compressed later according to the requirements.
 A steady shooting platform should always be used.

38. Shooting and Editing Video
 Good and even lighting is extremely important.
 Blue screen in digital video editing applications is a popular
technique for making multimedia.
 Wide panoramic shots and camera motion should be
avoided when shooting for a small computer window on
CD-ROM or the Web.

39. 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.

40. 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.

41. 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.

42. 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.

43. Special Effects
 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.

44. 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.