Compact Disc Read Only Memory CDROM

1
Compact Disc Read Only Memory (CD-ROM)

• Direkabentuk khas sebagai medium storan bagi
  komputer, in addition to uncompressed audio data.
• CD-ROM tracks dibahagikan kepada audio
  (corresponding to CD-DA) dan data types (data
  untuk komputer).
• Each tracks may contain exclusively data daripada
  jenis yang sama.

2
Blocks

• Merujuk kepada unit data dalam CD-ROM
• CD-ROM blok mengandungi 2352 byte
• Daripada 2352 byte ini , cuma 2048 byte (computer
  data) atau 2336 byte (audio data) boleh digunakan
  untuk data pengguna. Byte selebihnya digunakan
  untuk pengenalan bagi capaian rawak, juga sebagai
  lapisan pembetulan kesilapan bagi mengurangkan
  kadar kesalahan dalam data yang disimpan.

3
Modes

• Spesifikasi CD-ROM dibuat dengan objektif untuk
  digunakan bagi penyimpanan CD-DA data dan juga
  data yang boleh digunakan oleh komputer
  (termasuklah semua media-media lain selain
  audio).
• Mode 0, dimana semua 2336 byte data pengguna
  diset pada 0, digunakan bagi mengasingkan storage
  areas.

4
CD-ROM Mode 1

• Digunakan bagi storan data komputer
• Blok 2352 byte dipecahkan kepada
  kumpulan-kumpulan berikut
• 12 byte penyelarasan mengesan permulaan blok
• 4 byte header (byte pertama simpan minit, byte
  ke-2 simpan saat, byte ke-3 simpan nombor blok
  byte ke-4 simpan mode spesifikasi)
• 2048 byte data pengguna
• 4 byte EDC (Error Detection Control)
• 8 byte tidak digunakan
• 276 byte pembetulan ralat

5
CD-ROM Mode 2

• Storan untuk media-media lain (esp audio, video)
• Blok 2352 byte dibahagikan kepada
  kumpulan-kumpulan berikut
• 12 byte penyelarasan mengesan permulaan blok
• 4 byte header (rujuk Mode 1)
• 2336 byte data pengguna

6
Kekangan (Limitations) Teknologi CD-ROM

• CD mempunyai kapasiti yang tinggi kadar
  pemindahan data yang malar (constant)
• Capaian rawak ke atas track CD mengambil masa
  sehingga 1 saat, ianya masih boleh tolerate bagi
  audio playback
• Ini merupakan kekurangan berbanding cakera
  magnetik yang mengambil masa untuk capai data
  kurang 10ms (purata sekitar 6 ms)

7
Faktor yang menyumbang kepada capaian masa CD-ROM

• Synchronization time occurs because the internal
  clock frequency must be adjusted to be exactly in
  phase with the CD signal. Delays are in the range
  of milliseconds
• Due to the Constant Linear Velocity (CLV)
  playback of a CD, the rotational velocity at
  single speed is about 533 revolutions per second
  on the inside, but only 200 revolutions per
  second on the outside. The rotation delay
  describes the time it takes to find the desired
  sector within a maximum of one rotation and to
  correctly set the rotation speed. Depending on
  the device, this time can be about 300ms. For a
  CD-ROM device with a real 40-time data transfer
  rate and about 9000 revolutions per minute, the
  maximum rotation delay is about 6.3ms
• The seek time refers to the adjustment to the
  exact radius, whereby the laser must first find
  the spiral track and adjust itself. The seek time
  frequently amouts to about 100ms

8
CD-ROM Extended Architecture (CD-ROM/XA)

• Berdasarkan spesifikasi CD-ROM
• Dibangunkan oleh N.V. Philips, Sony Microsoft
• Tujuan mengendalikan output dari beberapa media
  secara selari
• Guna CD-ROM Mode 2 untuk menakrifkan blok-blok
  sebenar dengan medan subheader sebagai tambahan
  (menerangkan tentang seuatu blok/sektor). Ini
  membolehkan proses interleave beberapa jenis
  media. Namun sewaktu playback, aliran data
  individu diasingkan
• CD-ROM/XA membezakan blok-blok dengan 2 bentuk
  iaitu Bentuk 1 Bentuk 2.
• Kelebihan dalam 1 track, blok-blok boleh terdiri
  daripada media yang belainan

9
Bentuk 1

• Improved error detection correction
• 8 byte subheader
• 2048 byte data pengguna
• 4 byte error detection
• 276 byte pembetulan ralat

10
Bentuk 2

• Lebih data storan untuk pengguna. Lebih sebanyak
  13 berbanding actual data capacity.
• Kurang byte untuk pengendalian ralat
• Benarkan penyimpanan data audio video yang
  telah dimampatkan

11
Lanjutan Pembangunan Berasaskan CD-ROM

• Compact Disc Interactive
• Compact Disc Interactive Ready Format
• Compact Disc Bridge Disc
• Photo Compact Disc
• Digital Video Interactive
• Compact Disc Recordable
• Compact Disc Magneto Optical

12
Compact Disc Interactive

• Developed by N.V. Philips Sony prior to the
  specification of CD-ROM/XA
• Originally designed for consumer electronics as
  an addition to the TV set.
• 1991 marketed commercially, disappeared by end
  1997.
• Mengandungi format berdasarkan CD-ROM dengan
  interleaving dari pelbagai media support
  pemampatan pelbagai jenis media
• Perkakasan CD-I dikenali sebagai Decoder bersaiz
  sebuah VCR, consists of a main Motorola 68000
  processor with special video audio chips. Turut
  mengandungi CD Player dengan kawalan joystick dan
  antaramuka mouse.

13
Compact Disc Interactive Ready Format

• Menyediakan keperluan bagi format spesifikasi
  untuk cakera optikal yang boleh dimainkan samada
  oleh pemacu cakera CD-DA atau CD-I
• Untuk tujuan ini, kawasan track pregap
  diperbesarkan dari 2-3 saat kepada minimum 182
  saat. CD-I specific information disimpan di dalam
  kawasan ini, seperti maklumat tentang muzik, imej
  ataupun biography komposer atau conductor
• CD-I Ready Disc boleh dimainkan dengan 3 cara
• Menggunakan media CD-DA, hanya audio akan
  dimainkan sementara maklumat dalam track pregap
  akan diabaikan
• Hanya menggunakan CD-I data dalam kawasan track
  pregap. Data dari pelbagai media boleh dibaca,
  dipersembahkan atau diterjemahkan. CD-DA audio
  data of the track are not played
• Semasa audio playback, CD-I data dari track
  pregap akan dipersembahkan serentak dengan output
  audio. First, the CD-I data are read stored.
  Then the audio information is output together
  with the corresponding data from the track pregap
  (which were read beforehand!!).

14
Compact Disc Bridge Disc
15
Compact Disc Bridge Disc

• Seperti CD-I, ia jadi format spesifikasi untuk
  peranti output yang compatible dengan
  format-format CD yang berlainan
• CD-I Ready Disk mempunyai format disk yang tetap
  untuk peranti CD-DA dan CD-I, manakala CD Bridge
  Disc mempunyai format disk yang tetap untuk
  peranti CD-ROM/XA dan CD-I
• Mesti memenuhi spesifikasi CD-I dan CD-ROM/XA
• Semua tracks dengan data komputer mesti ditulis
  dalam CD-ROM Mode 2
• Semua tracks dengan data komputer boleh diikuti
  dengan semua tracks audio (CD-DA)
• Semua tracks dengan data ditandakan dengan
  CD-ROM/XA tracks

16
Photo Compact Disc

• Developed by Eastman Kodak and N.V. Philips is an
  example of CD Bridge Disc used for storing
  high-quality photographs
• Based on CD-WO, part of the Photo CD is delivered
  already written, and a second part can be written
  once
• Boleh dibaca dengan peranti CD-I atau CD-ROM/XA.
  Additionally, it can be read and written by CD-WO
  devices and by special Photo CD devices
• Proses terlibat
• Photographs are created using conventional
  cameras and films
• After film is developed, the picture is
  digitized. Each pixel is coded in 24 bits
• Photo then coded in up to six resolutions as an
  ImagePac. Each ImagePac requires 3-6 Mbytes of
  storage
• Images can be displayed using a computer or TV.
• Features lain termasuklah zooming, change
  resolution, modification, etc.

17
Digital Video Interactive

• Consists of compression and decompression
  algorithms highly integrated, dedicated hardware
  components for compression and decompression of
  video in real time a user interface (known as
  Audiovisual kernel, AVK) and the fixed data
  format.
• Perbezaan dengan CD-I, DVI not emphasis on CD
  technology but on the compression algorithms.
• DVI menggunakan CD-ROM Mode 1, dan AVSS
  (Audio/Video Support System) interleaved file
  format.

18
Compact Disc Recordable (CD-R)

• Seperti WORM boleh benarkan pengguna tulis sekali
  ke atas CD
• CD-R has a pre-engraved track.
• In all read-only CDs, the substrate ( a
  polycarbonate) adjoins the reflective layer. In
  CD-R, there is an absorption layer between the
  substrate and the reflective layer. Strong heat
  has the effect or irreversibly modifying this
  layer reflective properties for laser beams.

19
Compact Disc Recordable (CD-R)

• In the original state, a CD reader sees a track
  consisting of lands. Using a laser with the
  intensity of 3 or 4 times that of a read-only
  devices, the absorption layer in the area of the
  pre-engraved track is heated to above 250
  Celsius. This alter the material such that the
  reflected laser light now corresponds to a pit.
  This gives rise to the most noteworthy property
  of the CD-R. The data on the CD-R can be read by
  traditional devices designed exclusively for
  read-only CDs.

20
Compact Disc Magneto Optical

• Mempunyai kapasiti storan yang tinggi
• Benarkan seseorang menulis beberapa kali ke atas
  CD
• Spesifikasi dalam Orange Book
• Berdasarkan konsep polarization medan magnet,
  dimana polarization tersebut adalah disebabkan
  oleh heat atau kepanasan
• The block (sector) to be written is heated to
  above 150 Celsius. At the same time, a magnetic
  field about then times the strength of the
  Earths magnetic field is applied. At this point,
  the materials dipoles are polarized towards this
  magnetic field. A pit is coded with a
  downwards-facing magnetic north pole. A land is
  coded using the opposite orientation
• In order to erase a block (sector), the area
  around the block is subjected to a constant
  magnetic field while it is heated
• If the CD is illuminated by a laser, the
  polarization of the light changes depending on
  the magnetization of the CD. In this way, the
  information can be read.

21
Compact Disc Glossary

• Acess time The time required by a CD-ROM drive
  to read the data requested from the CD-ROM disc
  and send it back to the computer.ADPCM Adaptive
  Different Pulse Code Modulation is a method of
  compressed audio data storage in which it is not
  the value of the signal which is stored but the
  difference from the previous sample (or
  measurement). This means that only 4 bits are
  needed per sample rather than the normal 16
  bits.   In the CD-i standard, the levels A, B
  and C are recognized. B and C are also used in
  CD-ROM XA. The sample frequencies used to measure
  the audio signal are 37.8 KHz and 18.9 KHz for B
  and C respectively. This brings the band width
  (the maximum frequency to be reproduced) to 17
  and 8.5 KHz.   For level A, these figures are
  44.1 KHz 20 KHz. Using ADPCM, a maximum 16 - fold
  reduction in storage requirements can achieved
  (Level C, mono).AMS Automatic Mastering and
  Stamper making System.ATRAC Adaptive Transform
  Acoustic Coding A method of compression of audio
  signals as used for Mini Disc.

22
Compact Disc Glossary

• BER Bit Error Rate expressed as the number of
  correctly processed bits before a erroneous bit
  is detected. For CD-ROM the figure is 10 to the
  power 12.BLER Block Error Rate expressed as
  the number of blocks with at least I error
  against the total number of blocks
  measured.Block In CD-ROM technology the data is
  stored on the CD-ROM in blocks, sometimes called
  sectors or frames, of 2 KBte (2048 Bytes). Apart
  from the user-data, extra information is added
  (see Mode 1/2, Form 1/2).Byte A symbol or
  character, consisting of 8 bits.Caching The
  mechanism by which a cache is used to store
  recently reque- sted information. On the next
  request for the same information, the system
  retrieves it from fast cache- memory rather than
  from the slower medium.CD Bridge disc The CD
  bridge disc is a special type of CD-ROM XA disc
  with a CD-i application program. By using the CD
  Bridge disc concept, the discs can be played on a
  variety of players such as CD-i, CDROM XA, etc.
  Examples are Photo CD and Video CD.
• CD-i Compact Disc Interactive a system for
  presenting information (text, image and video) on
  a television screen. The standard is defined by
  Philips and Sony and contained in the Green Book.

23
Compact Disc Glossary

• CD-ROM Compact Disc Read Only Memory a
  storange medium which can only be read, based on
  audio CD technology.Maximum capacity for 74
  minutes 681984000 Bytes 650 MByte for 63
  minutes 580608000 Bytes 553 MByte where I
  minute 60 seconds I second 75 frames I frame
  2048 Bytes.CD-ROM XA XA stands for eXtended
  Architecture and is a standard for CD-ROM in
  which a number of options from CD-i have been
  added. These include audio compression (ADPCM),
  multi-channel audio (max. 16), file interleaving,
  user data (2336 Bytes/ sector), image compression
  capability, etc. A CD-ROM XA disc is a Mode 2
  disc, in which the data is located in Form 1
  (2048 Bytes/sector) or Form 2 (2336 Bytes/sector)
  sectors.DAT Digital Audio Tape, a 4 mm tape
  format also used for data storage.Data Capture
  Method of converting data from non-electronic
  data carriers (paper, microfiche, artwork, etc.)
  into a form which allows processing by
  computer.Data Compression A technique in which
  as much superfluous information as possible is
  removed from the data. Example a repeating
  sequence can also be stored as the value and the
  number of repetitions.

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Compact Disc Glossary

• DCC Digital Compact Cassette. The DCC system is
  an extension of the existing Compact Cassette
  standard, defining a magnetic tape system that
  includes recording and playback of digital
  data.Directory A file that contains information
  (name and location) about the files on a disk.
  Used in almost every storage medium (floppy, hard
  disk, CD-ROM).EDC Error Detection Code a
  checksum of the previous Bytes in the sector.
  This enables the, CD-ROM player to conclude
  immediately that a (read) error has occurred
  during the reading of the information. With the
  use of ECC, errors of this kind can be corrected
  to a certain extent.Floppy disk Removable
  magnetic 
• medium in a synthetic jacket. Information can be
  stored on it using a read/write head. The
  information is erasable.FMV Full motion, full
  screen video.Form 1 Used in CD-ROM. Division of
  the Mode 2 sector intoSync (12 Bytes). Header (4
  Bytes), Subheader (8 Bytes), User data (2048
  Bytes), EDC (4 Bytes), ECC (276 Bytes). This
  layout is used for normal data files (incl. Photo
  CD and Electronic Book).

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Compact Disc Glossary

• Form 2 Used in CD-ROM. Division of the Mode 2
  sector into Sync (12 Bytes). Header (4 Bytes),
  Subheader (8 Bytes), User data area (2324 Bytes)
  and 4 Bytes reserved or 4 Bytes for EDC. This
  layout is used for files where error correction
  is pointless or impossible due to their real-time
  character such as compressed audio or moving
  imagesGB GigaByte, 1024 MB 1024 x 1024 1024
  1,073,741,824 Bytes.Hard disk The hard disk is
  a permanent, (fixed) storage medium for computer
  data based on a rotating disc with a
  magnetically, sensitive layer. Information can be
  written on this and read again using a read/write
  head. The information stored is erasable.HFS
  Hierarchical Filing System, used by, Apple. Used
  for floppy and hard disks and for CD-ROM. Apple
  also supports the ISO 9660 standard.Injection
  Moulding The process in which polycarbonate is
  sprayed under pres sure against the stamper to
  produce the CD After moulding, an aluminium layer
  is added to the surface and then lacquered.

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Compact Disc Glossary

• Interactive Media Media in which the user is
  required/expected to take action to find
  information or in order to be provided with
  information.Interface The point of contact or
  border surface between two systems. These can be
  items of equipment (e.g. SCSI interface between
  computer and CD-ROM player) software modules
  (user interface).JPEG A compression algorithm
  defined by the joint Photographic Expert Group
  for continuous tone images (colour pictures
  Permitting loss of information non-essential for
  human observation, compression rates 10-301 can
  be achieved. "Loss less" compression cannot go
  beyond 8 1.Karaoke Japanese word for "empty
  orchestra". A form of entertainment where guests
  in a Karaoke bar can take the microphone and
  start singing.KB KiloByte 1024 Bytes.

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Links

• http//cui.unigue.ch/OSG/info/MultimediaInfo/Info/
  cd.html
• http//www.sit.wlv.ac.uk/c972722/CDROM/CDTypes.ht
  ml
• http//www.studio-systems.com/gloss/MayJune1995/81
  May-June2095.htm