Page 80 - DCAP303_MULTIMEDIA_SYSTEMS

Multimedia Systems

notes 5.10 Summary
5.11 Keywords
5.12 Review Questions
5.13 Further Reading

objectives

After studying this unit, you will be able to:
• Understand how video works
• Explain broadcast video standards
• Describe analogue video
• Explain digital video
• Understand digital video standards—ATSC, DVB, ISDB
• Describe video recording and shooting videos
• Explain video editing
• Understand optimizing video files for CD-ROM
• Describe digital display standards

introduction

Video is the technology that captures moving images electronically. Those moving images are
really just a series of still images that change so fast that it looks like the image is moving.
The term video commonly refers to several storage formats for moving pictures: digital video
formats; including Blu-ray Disc, DVD, QuickTime (QT), and MPEG-4; and analogue videotapes,
including VHS and Betamax. Video can be recorded and transmitted in various physical media:
in magnetic tape when recorded as PAL or NTSC electric signals by video cameras, or in MPEG-4
or DV digital media when recorded by digital cameras. Quality of video essentially depends on
the capturing method and storage used. Digital television (DTV) is a relatively recent format with
higher quality than earlier television formats and has become a standard for television video.

5.1 How video works?

When light reflected from an object passes through a video camera lens that light is converted
into an electronic signal by a special sensor called a charge-coupled device (CCD). Top-quality
broadcast cameras and even camcorders may have as many as three CCDs (one for each colour
of red, green and blue) to enhance the resolution of the camera.
The output of the CCD is processed by the camera into a signal containing three channels of colour
information and synchronization; pulse (sync). There are several video standards for managing
CCD output, each dealing with the amount of separation between the components of the signal.
The more separation of the colour information found in the signal, the higher the quality of the
image (and the more expensive the equipment).
If each channel of colour information is transmitted as a separate signal on its own conductor,
the signal output is called RGB (red, green and blue), which is the preferred method for higher-
quality and professional video work. Output can also be split into two separate chroma (colour)
channels, Cb/Cr (blue and red chroma components) and a luma component channel (Y), which
makes the dark and light part of the video picture. These components are often confused with
the YUV colour space in which time=Y, x-axis=U and y-axis=V.

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