Download Lesson #8 Optical Storage Media

Lesson #8
Optical Storage Media
8. Optical Storage Media - Copyright © Denis Hamelin - Ryerson University
Optical Storage Media
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Offers high density storage at low cost.
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CD
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DVD
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BD
8. Optical Storage Media - Copyright © Denis Hamelin - Ryerson University
History of Optical Storage
Media
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1982: CD (Philips/Sony)
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1983: CD-ROM
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1986: CD-I (Interactive) – carries
compression/decompression algorithms
1988: CD-ROM/XA (Microsoft) – optimized for
multiple media.
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1995: CD-RW (Read/Write).
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1997: DVD
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2006: Blu-Ray Disk (BD)
8. Optical Storage Media - Copyright © Denis Hamelin - Ryerson University
Basic Technology
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In optical storage media, information is
represented by using the intensity of laser light
reflected during reading.
Laser beam has wave length of 780 nanometers
and can be focused to a resolution of 1 micrometer.
In a polycarbonate substrate layer, there are
depressions, called pits, corresponding to the data
to be encoded. Area between the pits are called
lands.
8. Optical Storage Media - Copyright © Denis Hamelin - Ryerson University
Basic CD Technology
8. Optical Storage Media - Copyright © Denis Hamelin - Ryerson University
Basic CD Technology
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Substrate layer is smooth and coated with a thin
reflective layer.
Pits have a depth of 0.12 micrometers from the
substrate surface.
Laser hitting pits are reflected with weaker
intensity.
In contrast to magnetic disks, all data is placed on
one track (spiral) for continuous playback.
8. Optical Storage Media - Copyright © Denis Hamelin - Ryerson University
Basic CD Technology
8. Optical Storage Media - Copyright © Denis Hamelin - Ryerson University
Compact Disc Digital Audio
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CD s have a diameter of 12 cm and are
played at a constant linear velocity.
A CD track has approximately 20000 windings
(by comparison, a vinyl LP has approximately
850).
The length of a pit is always a multiple of 0.3
micrometer.
A change from pit to land and from land to pit
represents a binary “1”. No change means “0”.
8. Optical Storage Media - Copyright © Denis Hamelin - Ryerson University
Audio CD Technology
8. Optical Storage Media - Copyright © Denis Hamelin - Ryerson University
Audio CD Technology
8. Optical Storage Media - Copyright © Denis Hamelin - Ryerson University
Audio CD Technology
8. Optical Storage Media - Copyright © Denis Hamelin - Ryerson University
Eight-to-Fourteen Modulation
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Because the laser may not be precise enough to
detect land to pits changes, two lands and two pits
must always follow each other.
To synchronize speed, there can be no more than
ten consecutive zeros as channel bits.
So real bits do not always follow the pits and lands.
To do that the 8-to-14 modulation must be applied
(from a table).
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00000000 becomes 01001000100000
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00000001 becomes 10000100000000
8. Optical Storage Media - Copyright © Denis Hamelin - Ryerson University
Eight-to-Fourteen Modulation
8. Optical Storage Media - Copyright © Denis Hamelin - Ryerson University
DVD Technology
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DVD uses 650 nm wavelength laser diode light as
opposed to 780 nm for CD. This permits a smaller pit
to be etched on the media surface compared to CDs
(0.74 µm for DVD versus 1.6 µm for CD), allowing
for a DVD's increased storage capacity.
Each DVD sector contains 2,418 bytes of data,
2,048 bytes of which are user data. There is a small
difference in storage space between + and (hyphen) formats.
8. Optical Storage Media - Copyright © Denis Hamelin - Ryerson University
DVD Capacity
8. Optical Storage Media - Copyright © Denis Hamelin - Ryerson University
Dual Layer DVD
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Dual-layer recording (sometimes also known as
double-layer recording) allows DVD-R and DVD+R
discs to store significantly more data—up to 8.54
gigabytes per disc, compared with 4.7 gigabytes for
single-layer discs. Along with this, DVD-DL's have
slower write speeds as compared to ordinary DVD's
and when played on a DVD player, a slight transition
can be seen between the layers.
These DVDs are also known as DVD-9, compared to
the single-layer DVD-5.
8. Optical Storage Media - Copyright © Denis Hamelin - Ryerson University
Dual-Layer DVD
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A dual-layer disc differs from its usual DVD
counterpart by employing a second physical layer
within the disc itself. The drive with dual-layer
capability accesses the second layer by shining the
laser through the first semitransparent layer.
In some DVD players, the layer change can exhibit a
noticeable pause, up to several seconds.
8. Optical Storage Media - Copyright © Denis Hamelin - Ryerson University
Dual-Layer DVD
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There are two modes for dual-layer orientation. With
Parallel Track Path (PTP), used on DVD-ROM, both
layers start at the inside and end at the outside with
the lead-out. With Opposite Track Path (OTP), used
on many DVD Video discs, the lower layer starts at
the inside and the upper layer starts at the outside
where the other layer ends; they share one lead-in
and one lead-out. However, some DVD Video discs
also use a parallel track, such as those authored
episodically, as in a disc with several separate
episodes of a TV series; where the layer change is
in-between titles.
8. Optical Storage Media - Copyright © Denis Hamelin - Ryerson University
DVD Video
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Most consumer DVD Video discs use either 4:3 or
anamorphic 16:9 aspect ratio MPEG-2 video, stored
at a resolution of 720/704×480 (NTSC) or
720/704×576 (PAL) at 29.97, 25, or 23.976 FPS.
Audio is commonly stored using the Dolby Digital
(AC-3) or Digital Theater System (DTS) formats,
ranging from 16-bits/48 kHz to 24-bits/96 kHz format
with monaural to 6.1-channel "Surround Sound"
presentation, and/or MPEG-1 Layer 2 and/or LPCM
Stereophonic.
The DVD format remains the preferred one for the
release of older television programs and films.
8. Optical Storage Media - Copyright © Denis Hamelin - Ryerson University
Blu-Ray Disc
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BD are used for storing high-definition video,
PlayStation 3 video games, and other data, with up
to 25 GB per single layered, and 50 GB per dual
layered disc. Although these numbers represent the
standard storage for Blu-Ray drives, the
specification is open-ended.
The name Blu-ray Disc derives from the blue-violet
laser used to read the disc. While a standard DVD
uses a 650 nm red laser, Blu-ray uses a shorter
wavelength, a 405 nm blue-violet laser, and allows
for almost ten times more data storage than a DVD.
8. Optical Storage Media - Copyright © Denis Hamelin - Ryerson University
Blu-Ray Disc
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BD are used for storing high-definition video,
PlayStation 3 video games, and other data, with up
to 25 GB per single layered, and 50 GB per dual
layered disc. Although these numbers represent the
standard storage for Blu-Ray drives, the
specification is open-ended.
The name Blu-ray Disc derives from the blue-violet
laser used to read the disc. While a standard DVD
uses a 650 nm red laser, Blu-ray uses a shorter
wavelength, a 405 nm blue-violet laser, and allows
for almost ten times more data storage than a DVD.
8. Optical Storage Media - Copyright © Denis Hamelin - Ryerson University
Blu-Ray Video
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For video, all players are required to support MPEG2 Part 2, H.264/MPEG-4 AVC, and SMPTE VC-1.
MPEG-2 is the codec used on regular DVDs, which
allows backwards compatibility. MPEG-4 AVC was
developed by MPEG, Sony, and VCEG. VC-1 is a
codec that was mainly developed by Microsoft.
Discs encoded in MPEG-2 video typically limit
content producers to around two hours of highdefinition content on a single-layer (25 GB) BDROM. The more-advanced video codecs (VC-1 and
MPEG-4 AVC) typically achieve a video run time
twice that of MPEG-2, with comparable quality.
8. Optical Storage Media - Copyright © Denis Hamelin - Ryerson University
End of lesson
8. Optical Storage Media - Copyright © Denis Hamelin - Ryerson University