Sony DVD 01, DVD VIDEO Schematic

TechnicalTraining

DVD

JanArtsJean-PierreCorgiatti

IanPatienceJaumeVillellaWinfriedWeist

“”

English

CONTENTS

Introduction: The Diverse, High Performance World of DVD........................................................... 4

Chapter 1 The High Capacity Optical Digital Disc for a New Era

Key Points ...........................................................................................................................................5

DVD disc construction and high-density recording ..........................................................................6

■Two 0.6 mm thick substrates bonded back-to-back .................................................................................6

■Laser beam wavelength and NA of the objective lens...............................................................................6

Four types of high-capacity disc....................................................................................................... 8

■Data reading and storing methods ........................................................................................................... 8

Modulation and error correction in the DVD system.........................................................................9

■EFM PLUS modulation...............................................................................................................................9

■DVD error correction system....................................................................................................................10

Five diverse formats are used in the DVD format group.................................................................11

DVD file systems ...............................................................................................................................12

Questions & Answers........................................................................................................................13

What is Write-once DVD? Can pictures be recorded on DVD? What about Rewritable DVD?

Chapter 2 Features of the DVD-Video Format

Key Points .........................................................................................................................................15

DVD-Video technology in detail .......................................................................................................16

■DVD-Video realizes high quality pictures, high quality sound, and multiple playback functions.............16

■Data volume distribution according to software contents .......................................................................16

High image quality technology (1) MPEG2 picture compression ...................................................18

■Why is data compressed? .......................................................................................................................18

■Profile and level of MPEG2 ......................................................................................................................18

■Hybrid coding by combining three main methods...................................................................................19

Questions & Answers........................................................................................................................19

What is MPEG?

Spatial axis compression - discrete cosine transform....................................................................20

■DCT removes unnoticeable frequency elements .....................................................................................20

Time axis compression - predictive coding with motion compensation........................................21

■Using preceding and succeeding pictures to predict motion ..................................................................21

■Motion Compensation extracts only motion changes .............................................................................21

Time axis compression - GOP construction and bi-directional prediction....................................22

■GOP construction by I, P, and B picture ..................................................................................................22

■The P picture and B picture .....................................................................................................................22

Huffman coding.................................................................................................................................23

■Huffman coding: a statistical method for data compression...................................................................23

Questions & Answers........................................................................................................................23

What is 4:2:0 coding in MP@ML?

Are there any differences between DV and DVD data compression? ............................................24

Bit rate technology in DVD-Video (2) variable transmission rate....................................................25

■Variable bit rate allows highly efficient image storage .............................................................................25

DVD-Video’s superb audio capabilities ...........................................................................................26

DVD-Video’s high fidelity (1) - Dolby Digital (AC-3) .........................................................................27

■Various Dolby Digital (AC-3) modes.........................................................................................................27

■Full-band 5.1 channel surround ...............................................................................................................27

■High efficiency coding method of Dolby Digital AC-3 .............................................................................28

DVD-Video’s high fidelity (2) - MPEG Audio ....................................................................................29

■Multi-channel surround ............................................................................................................................29

■Features of the MPEG Audio system.......................................................................................................29

■MPEG Audio’s high efficiency coding method.........................................................................................29

DVD-Video’s high fidelity (3) - linear PCM Recording ..................................................................... 30

■Linear PCM delivers the highest level of sound quality ...........................................................................30

Multiple-language function...............................................................................................................30

■Multiple-language dubbing of up to eight languages ..............................................................................30

■Multiple-language subtitling of up to 32 languages.................................................................................30

Stream and packet transmission .....................................................................................................31

■“Stream” data flow...................................................................................................................................31

■Transmission by packet multiplexing .......................................................................................................31

DVD-Video interactive operation......................................................................................................32

■Title menu and DVD menu .......................................................................................................................32

■Multi-story function ..................................................................................................................................32

■Multi-angle functioning up to nine angles................................................................................................33

■Parental lock function (optional standard) ...............................................................................................33

■Multi-aspect ratio capability.....................................................................................................................34

Questions & Answers........................................................................................................................34

How does seamless playback work?

Copyright protection system in DVD-Video.....................................................................................35

■“Regional Code” controls playback in six regions of the world...............................................................35

■“Copy Protection System” links software and hardware .........................................................................35

DVD-Video software production ......................................................................................................36

■Telecine ....................................................................................................................................................36

■Authoring - the process ...........................................................................................................................36

■Authoring - MPEG2 video encoding ........................................................................................................36

■Disc manufacturing ..................................................................................................................................37

Chapter 3 Sony’s new DVP-S715 and DVP-S315 DVD players

Main Features ...................................................................................................................................39

Main Specifications of the DVP-S715 ..............................................................................................40

Main Specifications of the DVP-S315 ..............................................................................................41

Extremely high precision optical pickup network ...........................................................................42

■Dual discrete optical pick-up ...................................................................................................................42

■New digital RF processing LSI.................................................................................................................42

■New programmable DSP servo................................................................................................................42

■Tilt servo maintains disc reading accuracy..............................................................................................43

■Quick access drive...................................................................................................................................43

■Resonance-damping disc tray .................................................................................................................43

Questions & Answers........................................................................................................................43

What is jitter?

High precision digital image processing..........................................................................................44

■Smooth Scan easily indicates search direction .......................................................................................44

■Slow motion and frame-by-frame playback ............................................................................................44

■High-precision 10 bit video processing and D/A converter.....................................................................45

■Digital Noise Reduction (DNR) .................................................................................................................45

■Video pause with auto field/frame mode selection..................................................................................46

■High quality letter box conversion ...........................................................................................................47

High-end CD player technology for high-end sound ......................................................................48

■Sony’s new 96kHz/24 bit D/A Converter .................................................................................................48

■Variable Coefficient (VC) digital filter ........................................................................................................48

■24 bit processing for precise soundtrack decoding ................................................................................48

■R-core transformer...................................................................................................................................49

■Off-center anti-resonant feet....................................................................................................................49

■Ultra high-performance audio circuits .....................................................................................................49

■Optical and coaxial digital audio output terminals...................................................................................50

Questions & Answers........................................................................................................................50

How is AC-3 recorded on a laserdisc?

Full-function remote commander and GUI ......................................................................................51

■User-friendly design for ultimate enjoyment ............................................................................................51

■GUI makes operation easy.......................................................................................................................51

■Video bit allocation can be displayed ......................................................................................................51

■Multi-level dimmer....................................................................................................................................51

■Screen Saver 51

Manufactured under license from Dolby Laboratories Licensing Corporation. “Dolby”, the double-D symbol , “Pro Logic” and “AC-3” are trademarks of Dolby Laboratories Licensing Corporation.

Welcome to the next generation in

optical disc media

Announcing the Diverse, High Performance World of DVD

The digital audio era began in the fall of 1982 with the release of the Compact Disc and the CDP-101, the Sony’s first CD player. The CD represented a true breakthrough in sound reproduction. Just 12 cm in diameter, it was only a fraction of the size of vinyl analog records popular at the time. But the CD, with its highly dynamic, crystal clear sound, not to mention the sheer convenience of random access, soon eclipsed analog records to become a leading form of music software.

The CD format proved too good for music alone. In the 1980s, it was applied in the rapidly progressing computer field as a quick-retrieval data storage system called CD- ROM. Not only is CD-ROM software extremely convenient, it is also remarkably inexpensive to manufacture. The subsequent development of Video CD and Photo CD was proof that the era of optical disc media had arrived.

Interestingly enough, the CD was not the first consumer- use optical disc media. It was preceded by the LaserDisc in 1980. This 30 cm disc, roughly the same size as the analog record, was designed to hold up to one hour of high quality audio and video per disc side.

Although the LaserDisc and CD differ in size, signal recording system, and contents, they are fundamentally similar in their method of recording on micron-order pit rows and playback by laser

pickup. As the first step toward practical application of optical disc media, the development of the LaserDisc began in the 1960s with the dream of creating “records which can also display images.”

In the nearly two decades since the release of the LaserDisc, a broad array of technological advances in basic materials, hardware, software, and digital processing have given birth to an exciting new optical disc video format. DVD-Video is now a reality, offering superior performance in every parameter of operation.

DVD-Video, just one of the many proposed forms of the DVD format, is the same size as the CD, yet boasts far higher data storage capacity. In combination with the highly advanced MPEG2 data compression technology, an entire movie — with multiple soundtracks and subtitle choices — can be recorded and played back on a single disc with full-quality image and sound reproduction.

DVD-Video was joined by DVD-ROM, which was standardized at the same time, then followed by DVD-R and DVD-RAM, which were subsequently standardized, as universal formats. DVD-Audio is currently being studied for standardization. These media are expected to play a central role in the coming age of multi-media and information technology.

■History of Optical Discs

LaserDisc introduced

1980 1982 1991 1997

Compact Disc introduced

MO (magneto-optical disc) introduced

■Evolution of the CD format

Red

Book

1981

CD-DA

Yellow

Book

1985

CD-G

1985

CD-ROM

Green

Book

(International Organization for

Standardization format)

1986

1987 1996

CD-V

1987

ISO9660

CD-I

Orange

Book

1988

CD-ROM XA

(extended format)

1989

CD-R

White

Book

1992

Blue

Book

1994

Photo CD

CD TEXT

1996

CD Extra

Video CD

1996

CD-RW

DVD introduced

Chapter One

The High Capacity Optical Digital Disc for

a New Era

A remarkably large storage capacity, the primary feature of DVD, has been realized by higher recording density made possible by advanced technology developed after the introduction of the CD. The storage capacity of DVD is 4.7 GB (gigabytes) by recording on a basic single sided, single layer disc. This is approximately seven times greater than that of the CD.

In addition to this basic single side, single layer disc, there are three other types of discs: 1) the single sided, dual layer disc which can store 8.5 GB of data; 2) the double sided, single layer disc; and 3) the double sided, dual layer disc. The latter two, respectively are the

double-sided versions of the single side, single layer and single side, dual layer discs. At present, four types of discs have been standardized.

In addition to DVD-Video, DVD-ROM, DVD-R (writeonce media) and DVD-RAM (rewritable media), for which specifications have already been published, DVD-Audio is being studied for standardization. This makes for a total of five DVD categories.

In this chapter, our discussion is focused on the physical format and fundamental signal process. DVD-Video will be taken up in Chapter 2.

Key Points

●High density optical disc for the next generation which realizes a large capacity of 4.7 GB (single

side, single layer), approximately seven times greater than that of CD.

●Four disc types: single sided, single layer (4.7 GB); single sided dual layer (8.5 GB); double sided,

single layer (4.7 GBx2); double sided, dual layer (8.5 GBx2).

●Minimum pit length and track pitch are approximately one half of those of the CD. Primary

technologies which made this high density storage possible are:

(1) Short wavelength red semiconductor laser. (2) Improved numerical aperture (NA) of the objective lens. (3) Disc construction using thin 0.6 mm substrate.

●Signal processing capability for the optical disc system was improved in both modulation and

error correction.

●Five disc categories have been defined: DVD-Video, DVD-ROM, DVD-Audio, DVD-R, and DVD-

RAM.

●Making use of its large storage capacity and interactive characteristics, DVD is more than just a

video disc. In the coming multi-media era, DVD represents a new data medium for a variety of applications in many different fields.

DVD disc construction and high-density recording

t=1.2mm

t=0.6mm

thickness of the disc thickness of the disc

Even a single sided, single layer DVD has about seven times the storage capacity of CD. What has made this large storage capacity possible is new technology in high density recording and reproduction.

Minimum pit length in DVD is 0.4 microns, with a track pitch of 0.74 microns. Both are approximately half of those of the CD. This has been made possible by making the laser beam spot much smaller than that of the CD. The main technical approach used to make the

■Basic Specifications of DVD

DVD-Video/ DVD-ROM

(Single sided,

single layer type)

DVD-Video/ DVD-ROM

(Single sided,

dual layer type)

disc

diameter

disc

thickness

(two 0.6mm

substrates

bonded)

(two 0.6mm

substrates

bonded)

minimum

pit

length

maximum

pit

length

track pitch

sector

alignment

CLV

laser beam spot smaller is the use of a laser beam with shorter wavelength, and the adoption of a larger objective lens numerical aperture (NA). Improved signal processing of data encoding (modulation format) and error correction and reduction of data redundancy also contributed to an increase in storage capacity. In addition, the storage capacity of DVD can be greatly increased by using both dual layer and double sided configurations.

reference scanning

linear

velocity

ISO9660

file system modulation

UDF Bridge

(

UDF &

UDF Bridge

(

UDF &

EFM plus

(

8-16

)

EFM plus

(

8-16

)

correction

)

error

RS-PC

readout

wavelength

of laser

diode

(reference)

650/

635nm

650/

635nm

NA of

objective

lens

(reference)

0.6 4.7GB

0.6 8.5GB

data

capacity

CD-ROM

CLV EFM CIRC

ISO9660

0.45780nm

■Two 0.6 mm substrates bonded back-to-back

The DVD disc itself is 1.2 mm thick and 120 mm in diameter and is made of polycarbonate, the same as a CD. The disc consists of two 0.6 mm thick substrates bonded back-to-back, while the CD is composed of a single substrate. This has an advantage of minimizing the effects of the inclination of recorded surface against the incident laser beam (discrepancy against vertical angle) or tilt angle, thus reducing reading errors and contributing to higher storage density.

■Effects of tilt angle differ by disc thickness.

The thicker a disc is, the larger the difference in length there is between A and A’

■Relationship between the laser beam’s wavelength and the NA of the objective lens

The diameter of the laser beam spot is in proportion to the laser beam’s wavelength, and is in inverse proportion to the numerical aperture of the objective lens. In DVD, a red semiconductor laser beam with a short wavelength of 650 nanometers or 635 nanometers is employed, while the CD uses a 780 nanometer laser beam. The

numerical aperture (NA) of the objective lens of a DVD pickup is 0.6, larger than the 0.45 of the CD. This enables focusing the laser beam to a smaller spot than with the CD, so pit sizes and track pitch can be made smaller, resulting in higher storage density on a given disc size.

0.68GB

The larger the NA of the objective lens, the smaller the tolerance of the tilt angle. However, the DVD uses two

0.6 mm thick substrates bonded back-to-back, and necessary reading precision is maintained. The physical recording density of the DVD is 4.6 times as dense as that of the CD. In addition to these improvements in physical precision, improved signal processing in data encoding (modulation) and error correction also contribute to higher data capacity of the DVD.

■

DVD vs CD in pit length and track pitch

DVD

track pitch: 0.74 µm

beam spot Ø0.9 µm

minimum pit length:

0.4 µm

track pitch: 1.6 µm

beam spot ø1.4 µm

minimum pit length:

0.83 µm

Four types of high-capacity disc construction

Four different types of disc construction have been standardized: single sided, single layer; single sided, dual layer; double sided, single layer; double sided, dual layer disc. The single sided, single layer disc is quite similar to CD except that its substrate is 0.6 mm thick. The double sided, single layer disc is composed of two

■Single sided, single layer disc:

4.7 GB storage capacity

■Single sided, dual layer disc:

8.5 GB storage capacity

disc thickness

1.2mm

disc thickness

1.2mm

substrate

reflective layer

substrate

reflective layer

0.6mm

laser beam

0.6mm

single side, single layer substrates bonded back-toback. The single sided, dual layer disc is a single sided, single layer disc having one more storage layer beyond the first layer. To enable the pickup to read data on the second layer, the first layer is covered by semi-reflective material.

■Double sided, single layer disc:

9.4 GB storage capacity

■Double sided,

dual layer disc: 17 GB storage capacity

disc thickness

1.2mm

disc thickness

1.2mm

laser beam

substrate

reflective layer

substrate

reflective layer

substrate

semi-reflective layer

laser beam

reflective layer

0.6mm

semi-reflective layer

substrate

laser beamlaser beam

■Data reading and recording methods

In the case of the single sided, single layer disc and the single sided, dual layer disc, the data is read from one side of the disc as is done with CD. With the double sided, single layer disc and the double sided, dual layer disc, the data must be read from both sides of the disc. Data is recorded from the inner circumference to the outer, like with CD, except for dual layer discs (both single sided and double sided).

There are two methods of recording dual layer DVD. One method is to record data on both layers from the inner circumference to the outer (parallel track path) and the other is to record data from the inner circumference to the outer on the first layer and from the outer to the inner on the second layer (opposite track path). Data is regarded as a single volume in either method, and producers can select either method depending on the content of the software and the purpose of its expression.

semi-reflective layer

reflective layer

substrate

laser beam

■Recording method for the dual layer disc

parallel track path

opposite track path

lead-in area lead-out area

lead-out area

lead-in area

data area

middle area

data area

Modulation and error correction

■EFM PLUS Modulation

in the DVD system

In recording data on the disc, the “EFM plus (8-16 modulation) format” is employed to encode the source data for storage on the DVD. Digital signals are normally encoded prior to recording them on the storage media instead of recording them as they are (taking the CD and DVD as examples; the “0s” and “1s” of the original data are not formed in pits as they are). By EFM the signals, a much larger volume of data can be recorded on a track of the same length. EFM is performed to improve the efficiency (linear storage density) of the recorded wave form.

In CD and DVD, the original data constructed in 8-bit units are translated into blocks of 14-bit or 16-bit patterns using the conversion table. (This is called 8-14 modulation or 8-16 modulation.) The edges of pits pressed on the disc indicate where “1s” appear in the successive patterns of “0s” and “1s.” The principle

of the modulation format called Non Return to Zero Inverse (NRZI) is used here.

The 8-16 modulation of the EFM plus format used in DVD is the improved version of the 8-14 modulation of the EFM format adopted in the CD. This 8-16 modulation may appear inefficient when compared to 814 modulation because 16 bits are used instead of 14 bits. In actual practice, however, it achieves a higher storage density. A total of 17 bits (14+3=17) are required because 3 merging bits are used to link the blocks of 14 bits in the EFM, while a multiple number of conversion tables are used (only one conversion table is used in EFM) to suppress indispensable DC components needed to form the optical disc system and merging bits are not required in EFM plus. The EFM plus format increases storage density by approximately 6 % when compared to the EFM format. (Note 1)

Note 1: (17-16)/16=0.0625

■8-16 modulation and pit pattern

8-bit data

The original 8-bit data is

translated into a 16-bit pattern by

the conversion table.

EFM plus modulation (16 bits)

recorded wave form

Recorded wave form reverses phase

if "1" comes and maintains

the phase when "0" comes.

pit pattern

Boundaries between the pits and

intervening reflective area

on the disc, or pit edges, are "1s".

00000111

0010000001001000

■DVD error correction system

In digital data media, errors or data dropouts in recording data due to scratches on the disc, disc vibration and other causes need to be corrected. Error correction is done by adding error correcting codes. Data with those codes are modulated, and then pits are formed. By adding those codes, mistakes made in reading data are corrected. The ratio of added codes in the total data, which includes the original data, is called data redundancy. The

■Error correction system for DVD The following explains the principle of data correction in digital data recording:

original data

RS-PC (Reed-Solomon Product Code) system is used for error correction in DVD. This has more error correcting capability than the CIRC (Cross Interleave Reed-Solomon Code) used in the CD, and also boasts lower data redundancy. Burst error correction capability, which is expressed by how long a pit row on the disc can be corrected, of a DVD player is about 6 mm versus about 2 mm of a CD player.

011

error correcting codes are added

Digitized data are arranged in the table as shown on the left.

001

011

0 001 100

011

0 011 100

(B)

011

011 001

row error correcting codes

0 011

(a)

column error correcting codes

An error occurs

when reading data

on the disc.

0 011

(A)

locating and

correcting an error

For example, a code is added to make the number of “1” in the row and column even.

Taking (a) as an example, a code “1” is added to make the number of "1" in the row "001" even.

The number of “1” in the row and column is checked.

The number of “1” is decided to be even after a code is added, so an error must be generated somewhere in either row (A) or column (B).

The data where the row (A) and column (B) cross is erroneous data. There is a “1” which is an error and we know the correct value is “0”. The data is restored to the correct value.

Naturally, the error correction system actually employed is much more

complicated, and it can correct more complicated errors.

Five diverse formats make up the DVD format group

In the DVD format group, there are five format variations: DVD-Video, DVD- ROM, DVD-R, DVD-Audio, and DVDRAM. They can be classified by the kind of data application and whether it is read-only or read-writable. The physical and logical formats for each format are defined in published specifications; DVD-Video in Book B, DVD-ROM in Book A, DVD-R in Book D and DVDRAM in Book E. Specifications for DVD-Audio is currently under study as Book C, respectively Looking at

■Five DVD format variations

Designation

DVD-Video

DVD-ROM

Type Application Status of specs

Read only

High quality package media for movie film

software with pictures and sound

Large capacity data media that allows high

quality multi-media application programs

for use with computers.

these five DVD categories from the standpoint of the physical format; the read-only types such as CD-ROM (Book A), DVD-Video (Book B), and DVD-Audio (Book C) use the same format, while the recordable DVD-R (Book D) and DVD-RAM (Book E) use independently separate formats. As a file system for use with personal computers, the UDF subset is employed on the readonly disc to facilitate compatibility.

Specs published in Sept.

1996 (Book B)

Specs published in Sept.

1996 (Book A)

DVD-Audio

DVD-R

(

Write Once

DVD-RAM

(

Rewritable

*3.95 GB/single sided **2.6 GB/single sided

)

Read only

Write once

Rewritable

High sound quality package media specifically

for music

Large capacity and write once data media for

computers

Large capacity and rewritable data media for

computers

Under study

*Specs published in July

1997 (Book D)

**Specs published in July

1997 (Book E)

As of January 1998

DVD file systems

UDF (Universal Disc Format) is adopted as a file format in DVD. It was devised by OSTA (Optical Storage Technology Association, an international organization) which consists of some fifty optical storage media related companies. The “UDF-Bridge” shown in the figure below, which extends to DVD-ROM, DVD-Video,

■Format construction and applicable books

application layer

volume layer

physical layer

format name

DVD-ROM

video

data format

UDF-Bridge UDF

physical format

read-only disc

DVD-Audio, and DVD-R, means that the bridge format which makes the conventional ISO 9660 valid as a subset of the UDF for DVD is used. The ISO 9660, which was originally devised as the file format for CDROM, is used to make the DVD compatible with CDROM.

audio

data format

physical

format

write-once

disc

DVD-AudioDVD-Video

physical format

rewritable disc

DVD-RAMDVD-R

Book ABook Book B Book C Book D Book E

Questions & Answers

What is write-once DVD?

Write-once DVD, DVD-R, can be recorded only once. Its data recording layer is coated by a proprietary organic dye. Recording is performed by applying a powerful laser beam on the layer. Thermal change takes place at the spot radiated by the powerful laser beam and the light absorbing property of the spot becomes smaller than the part not radiated. In reading data, digital signals consisting of “0s” and “1s” can be retrieved by the change in reflectance of data reading laser beam like data is retrieved by existence of pits in the CD. Spots thermally changed do not change even when they are radiated by the relatively weak datareading laser beam and data once recorded cannot be rewritten or overwritten.

Data recording and playback principle of DVD-R

protective coating

reflective coating

organic dye

polycarbonate

cross section of the disc

spot not radiated by the laser beam

recorded

Dye on the spot chemically changes by radiation of a powerful laser beam and its light absorbing property also changes.

powerful laser beam

reading recorded unrecorded

recorded

unrecorded

spot

part

weak laser beam

Differences in the reflective ratio are obtained from the spot radiated by laser beam and the part not radiated.

Can pictures be recorded on DVD?

We have explained that DVD-Video is a read-only format and the rewritable DVD-RAM is currently still being discussed. Will a disc that can record video and audio with quality and time duration equivalent to DVD-Video be available from other format variations in the DVD group?

The answer is that it will be some time in the future until such a disc will be available for home use. The reasons are the lack of storage capacity (data capacity of DVD-RAM is about 2.6 GB which is still smaller than the 4.7 GB of DVD-Video) and some as-yet undiscovered technical breakthroughs such as video signal encoding LSIs. In addition to these technical obstacles, there are very important unavoidable problems in protecting the copyrights which cover various digital information, not to mention for moving pictures and sound. Sony is

presently engaged in various activities to address these problems.

What about Rewritable DVD?

This is called DVD-RAM, and is a rewritable type of DVD disc. For the data recording layer, it uses a metal compound that reverses its phase from a crystallized state (crystalline phase) to an amorphous state (non-crystalline phase) and vice versa by the methods used to heat and cool the compound. The compound is rapidly heated and cooled by radiating a powerful laser beam to create an amorphous state spot on the crystalline state recording layer to record data. This type of disc is generally called a “phase change optical disc” because data is read using diverse reflectance of the amorphous state spots and the crystalline state parts caused by phase transition.

Data can be written repeatedly on the disc because amorphous state spots revert to a crystalline state if a weak laser beam is radiated on them and then cooled gradually. By controlling the power of laser beam radiated on the recording layer, simultaneous erasing and writing or direct overwriting can be performed.

phase change recording principle

recording power

laser

power

media

amorphous state

(molecular arrangement

diagram)

laser

(molecular arrangement

crystalline state

diagram)

erasing power

read-out power

Chapter Two

Features of the DVD-Video Format

The world of DVD begins with the advent of DVD-Video, while the world of CD began with the music CD (CDDA).

As the storage capacity of DVD was initially aimed at enabling the recording of an entire movie on a single disc, DVD-Video is designed to make the dream of enjoying pictures and sound with theater quality in the

home entertainment. As a new home entertainment media, DVD-Video has many features which have not been available from conventional package media. In this chapter, we will highlight the technology which has realized high quality video and audio from a compact 120 mm disc, and describe the many unique features

Key

●An entire movie can be stored on a disc the same size as a CD by making use of its large

storage capacity.

●Picture quality close to that of the Digital Video Format D1 used for professional video

masters has been realized by the adoption of MPEG2 compression.

●The same realistic sound and excitement as in movie theaters can be enjoyed in homes

through the high-fidelity 5.1 Channel Surround of the Dolby Digital (AC-3) System, and the high-fidelity 5.1/7.1 Channel Surround of the MPEG system.

●Interactive software, with features such as the multi-story function which allows users to

select a story and the multi-angle function for the selection of viewing angles, can be designed.

●The multi-language function allows dubbing of up to eight language soundtracks, and

subtitles in a maximum of 32 languages. The multi-aspect function enables the reception of wide pictures on your TV screen.

DVD-Video technology in detail

■

DVD-Video realizes high quality pictures, high quality sound, and multiple

playback functions.

The main features of DVD-Video can be summarized as high quality pictures, high quality sound, and multiple playback functions which are made possible by its large storage capacity and digital signal processing. In terms of picture quality, high quality images have been realized with 500TV-line resolution, better than either laserdisc or CD-Video.

The Dolby Digital (AC-3) System and the MPEG Audio System are adopted for sound in addition to the linear PCM audio. The 7.1/5.1 channel surround in the MPEG system reproduces high quality sound, while the 5.1 channel surround in the Dolby Digital (AC-3) system offers high fidelity sound with a very impressive and realistic sound field not available with Dolby Pro Logic.

Using these high quality pictures and high quality sound The most remarkable feature of DVD-Video is that it offers both the highest picture quality of home video media and

as a basis, interactive functions such as the multi-story,

multi-angle, and multi- language functions are also

achieved. the capability to record an entire movie, which requires a long recording time, all available on a single disc the same size as a CD.

■Video and sound specifications for DVD-Video

DVD-Video

video compression system

resolution (pixels)

horizontal resolution

compression ratio

video

video bit rate

field/frame

aspect ratio

audio

audio system

audio bit rate

audio

number of channels

quantization bit sampling

frequency

others

Note 1: In the case of PAL, DVD-Video is not compatible with the high definition system. Note 2: Either Dolby Digital, MPEG or Linear PCM can be selected for each audio system.

subtitles

MPEG Linear PCM

max. 912 kbps

(per stream)

max 7.1 ch. /

stream 48 kHz 48 kHz

MPEG2 (MP@ML)

720 x 576 pixels (Note 1.)

approx. 500 TV lines

approx. 1/40

9.8 Mbps, max. (variable) field/frame

4:3/16:9 (pan scan/letter box)

8 streams, max. (Note 2)

Dolby Digital (AC-3)

max. 448 kbps

(per stream)

max 5.1 ch. /

stream

2 bits, run length bit map system,

32 streams, max.

max. 6.144 Mbps

16-bit, 20-bit, 24-bit

(per stream)

max 8 ch. /

stream

48 kHz, 96 kHz

approx. 250 TV lines (same as VHS)

Video CD

MPEG1

352 x 286 pixels (Note 1)

approx. 1/140

1.15 Mbps (fixed) frame

4:3

2 channel (stereo)

MPEG1 layer 2 224kbps (fixed)

2 ch only

16-bit 44.1kHz

open caption only

Dolby Digital (AC-3): 1 stream,

Laserdisc

analog

approx. 420 TV lines

analog

4:3

analog 2 channel,

digital 2 channel (16-bit/44.1 kHz)

analog 1 channel,

digital 2 channel (16-bit/44.1 kHz)

open caption, closed caption

■Data volume can be distributed according to contents to be recorded.

DVD may be regarded as a large container of digital data and DVD-Video stores pictures and sounds in it as the main contents. DVD-Video features superior flexibility in accommodating the source, including subtitles and dubbing in multiple languages. Data is appropriately distributed depending on contents of the source within the framework of the total storage capacity. For example, when recording a movie, whether subtitles and

dubbing are recorded in several languages, or just in a single language, will make the recording time much different for the same title of software. When recording a music clip which does not require as much recording time as a movie, its sound can be recorded by the linear PCM format without compressing the sound since there is a plenty of room in terms of total storage capacity.

■One movie (av. 3.5 Mbps) + subtitle in one language + surround soundtrack in one language = about 160 minutes of recording time = 4.673 GB data volume

■One movie (av. 3.5 Mbps) + subtitles in 4 languages +surround soundtracks in 3 languages = about 133 minutes of recording time =

4.680 GB data volume

■One music clip (av. 6.5 Mbps) + 48 kHz 20-bit 2 channel linear PCM audio = about 74 minutes of recording time = 4.673 GB

0.010Mbps

0.384Mbps

3.5Mbps

subtitles x 1 (ex: Japanese)

surround audio 1 (ex: English)

video

3.894Mbps × 160

time

minutes =

4.673GB < 4.7GB

160

minutes

3.894Mbps

0.040Mbps

0.384Mbps

subtitles X 4 (ex: Japanese/English/Chinese/Arabic)

surround audio 1 (ex: English) surround audio 1 (ex: French)

surround audio 1 (ex: Spanish)

3.5Mbps

video

4.692Mbps × 133

time

minutes =

4.680GB < 4.7GB

Recordable data volume is the same in all examples.

133

4.692Mbps

minutes

1.92Mbps

6.5Mbps

20-bit 2 channel

linear PCM audio

8.42Mbps × 74

video

time

minutes =

8.42Mdps

minutes

4.673GB < 4.7GB

The high image quality technology of DVD-

Video (1) MPEG2 picture compression system

■Why is data compressed?

The data volume which can be stored on a CD is 5440 Mbits [Note 1] (680 MB). In the case of a music CD, digital audio data equivalent to 74 minutes of playing time can be stored on one disc. If picture signals in the PAL format are digitized, data volume for one minute will be more than 160 Mbits [Note 2] without compression and the data volume which can be stored on one disc will be less than 4 minutes of recording time even if a 4.7 GB DVD disc is used, and less than 34 seconds if stored on a conventional CD.

Storing 74 minutes worth of picture data on a Video CD was made possible by reducing the number of picture elements by half in both the vertical and horizontal directions to 352 x 286 pixels, and then finally reducing the data to 1/140 by using the MPEG1 compression system.

What made it possible to store picture data for 133 minutes (note that most popular movies are within 133 minutes) with a resolution of 720 x 576 pixels (corresponding to PAL) on a DVD-Video disc (single

side, single layer) was the adoption of the efficient data compression [Note 3] of the MPEG2 system in addition to tremendous improvements in disc storage capacity.

Note 1: 5440 Mbits is a simply converted figure of 680 MB based on 1 byte = 8 bits. Note 2: Calculated on 25 pictures with 720 x 576 pixels a second providing 8 bits to luminance and 8 bits to color per pixel. Note 3: The compression ratio is about 1/40, lower than that of Video CD.

■Playing time of movies

movies of over 133 minutes playing time: 7%

movies of less than 133 minutes playing time: 93%

At present, about 93% of popular movies are less than 133 minutes long

■Profile and level of MPEG2

MPEG2 was originally designed as a universal encoding system which can also be used in transmission media for communication applications. The “profile (five types)” is used to indicate combinations of functions suitable to a number of applications to maintain compatibility between media, while the “level (four types)” is used, and both are prescribed in the MPEG2 format

■Currently prescribed profiles/

Profile

Level

High 1920 × 1080 × 30

1920 × 1152 × 25

High-1440 1440 × 1080 × 30

1440 × 1152 × 25

Main 720 × 480 × 29.97

720 × 576 × 25

Low 352 × 288 × 29.97

Note 1

Simple Main SNR Scalable

MP@HL

US digital HDTV

MP@H1440 HP@H1440

SP@ML

Digital

transmission

cable TV

MP@ML

DVD-Video, Digital satellite

broadcasting

(PerfecTV and others)

MP@LL

specifications. Of the eleven currently proposed profiles and levels, what was adopted for DVD-Video is “MP@ML (Main Profile/ Main Level ).” Until digital HDTV formats become popular in the future, many different applications other than DVD-Video may be put into practical application using the MP@ML standards.

Note 2

Note 3

SNP@MP

SNP@LL

Spatial Scalable

SSP@H1440

European digital

HDTV

High

HP@HL

HP@ML

Note 1: Shows the standard number of horizontal pixels x vertical pixels x frame frequency Note 2: SNR = Signal Noise Ratio Note 3: MP@ML = Main Profile at Main Level

■Hybrid coding by combining three main methods

Roughly speaking, the MPEG2 (MPEG1 is also the same in basic concept terms) motion picture compression method is a combination of three main methods; “DCT (Discrete Cosine Transform)” which uses correlation in moving pictures to compress data, “Motion Compensation” which uses correlation between pictures to compress data, and “Huffman Code Processing” which employs correlation of code rows.

DCT uses the correlation of the spatial direction of pictures to remove the redundancy of data in the spatial axis, and Motion Compensation uses the correlation of the time direction in pictures to remove the redundancy of data in the time axis. In Motion Compensation, data is compressed to about 1/2; by DCT, 1/10 to 1/20; and by Huffman Code Processing, 2/3 to 1/2. Data is compressed to roughly 1/40 of the original volume in total. Reducing data to 1/40 means that picture signals

■Picture compression in DVD-Video

DVD-Video

of 240 Mbps can be sent at the rate of 6 Mbps, or 160 Mbps at 4 Mbps.

Compressing and decompressing motion pictures by these methods require an enormous amount of complicated calculation. The LSI of MPEG2 decoder circuits performing these calculation at high speed has made commercialization of the DVD-Video player possible.

The superior features of DVD-Video (employing MPEG2) over the video CD (which uses MPEG1) are: 4 times the number of picture elements (2 times each the in horizontal and vertical directions) and pictures are interlaced at 60 fields/second (MPEG1 is non-interlaced with 30 frames/sec.). MPEG2, the higher standard, is compatible with MPEG1.

data is compressed to about 1/40 on average by MPEG2

video data

input

motion compensation

(compressed by

correlation between

pictures), about 1/2

Discrete Cosine

Transform (compressed

by correlation within pictures), about 1/10

Video CD

data is compressed about 1/140 on average by MPEG1

video data

input

motion compensation

(compressed by

correlation between

pictures), about 1/5

Discrete Cosine

Transform (compressed

by correlation within pictures), about 1/14

Questions & Answers

What is MPEG?

MPEG stands for the Moving Picture Experts Group. This is the popular name of the working committee of experts who worked on encoding motion pictures as a sub-group (WG11) to JTC1/ SC29 of ISO/ IEC. The MPEG name is also used for the standard agreed on in this committee and approved as the international standard by ISO/IEC.

MPEG2 is a more sophisticated, more powerful standard of MPEG1, which was adopted in 1991 as

variable rate

Huffman Coding

(compressed by

correlation of code

rows), about 1/2

Huffman Coding

(compressed by

correlation of code

rows), about 1/2

compression

data is distributed

efficiently according to

difference in

video data volume

fixed rate

compression

data is distributed

evenly regardless of

differences in

video data volume

picture quality nearly equivalent to

studio-use

master tape

(D1)

picture

quality equivalent to

home use

VHS video

the standard for CD-ROM. MPEG2 was adopted in 1994 as the universal coding system for various transmission media including broadcasting and communication as well as for storage media such as optical disc.

The formal names of standards are ISO/IEC CD11172 for MPEG1 and ISO/IEC 13818 for MPEG2.

Spatial axis compression -

discrete cosine transform

■DCT removes unnoticeable frequency elements.

The nature of human perception is deeply considered in the compression of data for both video and audio. Human vision perceives pictures with some of high frequency elements omitted the same as pictures without any omissions. The total data is reduced by omitting unnoticeable frequency elements selectively after picture signals are resolved in several frequency element groups. The frequency element resolving process of MPEG2 (and MPEG1 is basically the same) is

■Basic concept of spatial axis compression

frequency A

original wave form

resolution

called the “Discrete Cosine Transform” method and selective omission of specified frequency elements taking advantage of limitations in human perception is called the “Quantize Matrix” method. These processes are done with dividing a frame of the picture in blocks of 8 x 8 elements (6480 blocks in total) and the luminance levels of the elements in each block are converted into values, and then are converted into frequency element data.

frequency B

freq A + freq B + freq C

frequency C

■Encoding process for spatial axis compression

one frame is

576 elements

Changes in luminance and color are small in some parts of a frame (low frequency) while changes are large in other parts (high frequency) and a frame can be considered as an overlaid composite picture comprised of a very low frequency picture, a low frequency picture, a high frequency picture, and a very high frequency picture.

divided into

6480 blocks.

720 dots

one frame is divided in blocks of 8 x 8 elements.

One frame is divided into small blocks, and luminance and color values of picture elements in each block are converted into numerical data. Then, the data is converted by DCT into an 8 x 8 block of frequency data.

frequency D

(high frequency elements)

removed selectively

Larger picture element values, distributed at random before the DCT conversion, tend to gather in low frequencies region (upper left area of the block) by the DCT conversion.

Values after conversion are divided by a specific number and the remainders are rounded (quantization step) to get many 0s line up in higher frequency regions (lower right area of the block). Removing these zeros (higher frequencies region) compresses the total data.

Time axis compression -

predictive coding with motion compensation

■Predictive cording constructs image by predicting motion from preceding and

succeeding pictures

An image in PAL television and video is composed of 25

synthesizing with the differential to reproduce pictures. frames/second (a frame consists of 625 scanning lines) and the display equipment reproduces a picture of 50 fields/second since it is scanned by interlacing to eliminate flickering. A large part of each picture is made of the same elements if continuous 25 pictures per second are compared with each other. And, they do not change much in a short time.

The method to reconstruct the original picture by

extracting and coding the differential between

continuous pictures is called “Predictive Coding”

because the current picture is predicted from the picture

immediately preceding it. As described in detail in the

following section, “Time axis compression, GOP

construction and bi-directional prediction, ”MPEG If there is a changing part in 25 pictures, the data volume necessary to store and reproduce the picture will be much smaller if only the changed part (differential) is

provides the coding to predict the current picture from

the immediately preceding and succeeding pictures on a

bi-directional prediction. stored and the other part is stored for one picture for

■Motion Compensation extracts only motion changes

There are two types of changing parts or parts with motion in pictures: one does not change its shape but changes its position as time elapses, while the other changes its shape as time elapses. Data of the shape should be used as it is for the former. The amount of position change without changing shape which takes

place with time, or the amount of movement, is called

the “motion vector.” The original picture can be

reconstructed when reproduced (in the decoding

process) with smaller data volume by coding only the

movement. This method which uses the motion vector is

■Predictive coding and motion compensation

(1)

(1)—(2)

(2)

1. Pictures (1) and (2) to be reproduced as time elapses have many elements common to each other. Differential or (1) minus (2) is extracted and (2) is reproduced by synthesizing the differential with (1).

Preceding frame

Current frame

The position in the

2. In the motion compensation process, pictures are divided into blocks and the motion vector which indicates the amount of movement is extracted and coded for the part whose position changes, without changing its shape. By combining this motion compensation with predictive coding, data is more efficiently compressed.

Time axis compression -

GOP construction and bi-directional prediction

■GOP construction by I picture, P picture, and B picture

To perform predictive coding employing motion compensation, MPEG2 uses GOP (group of pictures) construction made of three elements called the I picture, P picture, and B picture and MPEG2 organizes roughly 15 consecutive video frames into GOPs. The I picture (Intracoded picture) is compressed by DCT using information within the frame only without predicting the motion from the preceding frame.

If pictures constructed by the predictive coding are successively lined up, pictures cannot be displayed instantly when accessed at random. Then, the standard

for access is made periodically to respond to random accessing. The I picture is for maintaining independence from the GOP, so to speak.

The frequency of the I picture is normally 1-I picture/ 15 frames it is decided based upon the random access capability required for applications. The data volume of an I picture is 2 to 3 times that of the P picture and 5 to 6 times that of the B picture. The GOP is the group of pictures from one I picture to the next I picture. Thus, in simple terms, picture prediction is performed within pictures in the same group.

■An example of picture arrangement in GOP

.... I

B B P B B P B B P B B P B B I ....

GOP

I picture = Intracoded picture P picture = Predictive coded picture B picture = Bi-directionally predictive coded picture

Time

■The P picture and B picture

The P picture (predictive coded picture) is made on the basis of the I picture by predictively encoding the immediately preceding picture. The P picture may be defined as an “interframe forward direction predictive coded picture” in relation to the I picture, which itself is an “intraframe coded picture.” The B picture is a “bi-directional predictive coded picture” and is made by predicting two P pictures, the preceding and the succeeding. Taking a close look at the relationship between the I picture, P picture, and B picture in a GOP, the first step prediction made from the I picture located at the beginning of the GOP is performed in the forward direction and the P pictures are made. At that time, the P pictures are positioned jumping over

■Forward and bi-directional

a multiple number of B pictures to be constructed later. A multiple number of B pictures are made by the second step prediction from the first I picture and the P picture coded at the first step prediction (bi-directional prediction) and they are positioned between the I picture and the P picture. Another set of B pictures is made between the first P picture and the second P picture. The B picture when decoded compensates motion using two motion vectors and two reference pictures, preceding and succeeding. Bi-directional prediction, a feature of MPEG, uses two pictures, the past and future pictures timewise, for prediction to achieve highly efficient prediction.

IBBP

bi-directional

prediction

forward

prediction

The P picture is constructed by forward predicting the immediately preceding I picture or P picture while the B picture is made by bi-directional prediction using the immediately preceding and succeeding pictures.

Huffman coding

■Huffman coding: a statistical method for data compression

In addition to motion compensation, which removes data redundancy using correlations of the time axis in pictures, and DCT which removes data redundancy employing correlations of spatial axis in pictures, MPEG2 (MPEG1 is basically the same) uses a method called Huffman coding to achieve a further reduction in data redundancy. Huffman coding uses correlation in the code row made by MPEG processing to compress data (for example, five

Questions & Answers

What is 4:2:0 coding in MP@ML?

In MP@ML (Main Profile at Main Level) of MPEG2, a component system called “4:2:0” is adopted for encoding video signals. Numbers 4, 2, and 0 indicate the sampling frequency ratio of the luminance signal (Y) and two color differential signals (Cb and Cr) included in the horizontal scanning lines of video pictures, or the resolution ratio. For one picture element [Note 1], 8 bits are used for luminance and 8 bits each are used for color differential. The eye is not so sensitive to color as it is to luminance, and because the human eye is unable to perceive the reduction of color information as picture quality degradation in relation to luminance information, data can be compressed with no perceivable visual difference.

Pictures without color information reduction are called “4:4:4,” pictures reduced to half in the horizontal direction called “4:2:2,” and pictures reduced to half in both the horizontal and vertical directions are called “4:2:0.” In the “4:2:0”system, color information is one fourth of luminance

consecutive 0s are expressed as 0 x 5 instead of lining up five 0s). This may be called a “statistical” method if the motion compensation is called a “time” method and DCT a “spatial” method. Picture data is compressed spatially, statistically, and chronologically in MPEG2 and the total volume of codes generated is controlled by the quantization step for efficient data transmission.

information. The DV system, which has achieved excellent color reproduction for home use digital video, employs a “4:1:1” type component signal system that reduces color information to one fourth of luminance information and its data volume is the same as the “4:2:0” of the MP@ML of MPEG2. The “4:2:0” [Note 2] coding system is normally processed and output as “4:2:2” after lines are supplemented by processing within the LSI.

Note 1: In MPEG2, 8 bits are used for each of luminance Y, and color differential Cb and Cr in one picture element (3 X 8 = 24 bits). Note 2: The sampling frequency for all of Y, Cb, and Cr is 13.5 MHz in “4:4:4.” In “4:2:2”, 13.5 MHz for Y, 6.75 MHz for Cb and Cr. In “4:1:1”, 13.5 MHz for Y, 3.375 MHz for Cb and Cr. In ”4:2:0”, 2 lines with different sampling rates are alternatively repeated. One is 13.5 MHz for Y, 6.75 MHz for Cb and Cr is not sampled, while the other is 13.5 MHz for Y, Cb

Are there any differences between DV and DVD data compression?

The DV format of digital video recording is available as home use video media. It is quite different from DVD-Video in terms of compression because of the basic physical difference between the two forms of media, magnetic tape and optical disc. Moreover, the DV format uses only “within picture correlation’’ compression while DVD employs both ”within picture correlation” and “time axis correlation” compression.

What is the reason for this? DV was designed from the very beginning as a means to provide video recording and playback in the home, so tape editing at any point is as an important requisite as recording and playback. Data compressed on the time axis has to be decompressed each time it is played back or edited and data must be re-

compressed on the time axis to keep the data on the tape. This requires tremendous signal processing power, and is very inefficient.

For this reason, taking advantage of the far larger storage capacity of tape over disc,“ within picture compression” is used in DV for compressing data on the tape while DVD must also rely on “time axis compression” because of capacity limitations.

In addition to DVD, MPEG2 can also be applied in digital TV broadcasting, and is expected to be advantageous in multi-channel broadcasting. To make this possible, the bandwidth per channel must be kept as narrow as possible, so time axis compression will be employed.

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