Multimedia System & Design Ch 5 video

Multimedia System and Design
(Video)

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.
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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.

Video Concept
• However digital is much cheaper. Recording
an album with analog technology can
require a whole studio full of equipment,
but with digital recording technology, it’s
possible to record a whole album in a
bedroom on a laptop.

Broadcast Video Standards
National Television Standards Committee
(NTSC):
Named after the National Television Systems
Committee, which developed it, this standard
is used in all of North and South America,
except Brazil, and in much of East Asia.
– 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.

Phase Alternate Line (PAL) and Sequential Color and Memory (SECAM):
PAL standard is used in western Europe, including the United
Kingdom but excluding France, and in East Asia, including
Australia.
SECAM standard is used in France, eastern Europe, the Near East and Mideast, and
parts of Africa and the Caribbean.
• 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.

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.

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.

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,
difficult to edit.

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.

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

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

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

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.

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.

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.

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.

image resolution mean
• Resolution refers to the number of pixels in an
image.
• Resolution is sometimes identified by the width
and height of the image as well as the total
number of pixels in the image.
• For example, an image that is 2048 pixels wide
and 1536 pixels high (2048X1536) contains
(multiply) 3,145,728 pixels (or 3.1 Megapixels).

How big a print can I make?
• Example, you have a 640X480 image and you
want to print it at 200 dpi (dots or pixels per
inch).
• 640 divided by 200 equals 3.2 and 480 divided
by 200 equals 2.4 so if you print this picture at
3.2"X2.4" you will get a print with 200 dots
per inch.
• We recommend 200 dpi as a minimum for
good quality prints.

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.

3. 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 8 bit (256 colors)16 bit

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.

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.

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

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

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.

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.

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

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
compression programs, including JPEG (Joint
Photographic Experts Group) and MPEG
(Motion Picture Experts Group).

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.

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.

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

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.

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 and static situations

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.

Analog Vs Digital

Multimedia System & Design Ch 5 video

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