A Day at the DVD Forum: technical notes.
>>From - Mon Apr 22 21:47:12 1996
Newsgroups: sci.engr.television.advanced,alt.video.DVD,rec.video,comp.compression,alt.video.laserdisc
From: cfogg@chromatic.com
Subject: A Day at the DVD Forum: technical notes.
Followup-To: alt.video.DVD
Date: Mon, 22 Apr 1996 10:43:29 GMT
Title: DVD Notes from DVD Forum
Draft: 1.0
From: C. Fogg <cfogg@chromatic.com>
Date: April 11, 1996
These are my notes from attending the DVD Forum held at the Westin
Santa Clara hotel in Santa Clara, California April 10 and 11, 1996.
Some facts are summarized from the booklet distributed at the meeting.
Additional data has been added from verbal presentations and my own
preconceptions. HTML version some day, perhaps with illustrations...
WARNING: This document has been slapped together so kindgly forgive
any errors (read: you're lucking you're getting this in the first place :-)
Number one question: how do I get the DVD spec ?
=================================================
At the time of this forum, a new spec was just being drafted.
This should delay any distribution for a few weeks.
Currently, it costs $5,000 USD (U.S. Dollars) to join the DVD
Consortium, which has been the only way to obtain a legal copy of the
spec. This policy is expected to change soon. But note that today it
still costs real money to obtain copies of the old CD books (Blue,
White, Green, Red, etc.)
The DVD Consortium also wishes to improve the "dearth" of technical
information on the World Web Web/Internet.
Forum
=====
The Forum was hosted by Matsushita, Mitsubishi, Philips,
Pioneer, Sony, Thomson, Time Warner, Toshiba, and JVC.
The General Session ran during the morning hours. The
Hardware/Component, Media Software, and Physical breakout sessions ran
as parallel tracks in the afternoon.
The general session started with overviews of the DVD books and ended
with a panel of Hollywood home video studio executives, followed by
another panel of game developers. Most of the audience (~500 people
each day) originated from the hardware sector (semiconductor, board
vendors, etc.) rather than the software sector (game producers,
studios, post-production houses).
==========================================================
BOOKS OVERVIEW
==========================================================
The there applications of DVD are Video, Audio, and ROM. All three
discs types are built upon the same physical specification and file
structure.
Part 3 Video Audio
Application Specs Specs
Part 2 UDF UDF
File system UDF-Bridge (M-UDF + ISO 9660) Format Format
Part 1 Physical Physical
Physical Physical format Format Format
Disc specifications Disc specs Disc specs
(Read-Only Disc) Write-once Rewritable
Book Book A Book B Book C Book D Book E
Read Only Video Audio Write-Once Rewritable
Specs Specs Specs Specs Specs
Notes:
- The DVD Audio (Book C) is expected in Summer 1996.
- A blue laser version of the physical books (A, D, E) is expected
by the year 2000.
Structure of Video Book (Book B): Physical part
===============================================
1. General
- scope
- general parameters
- normative reference
- notations
- terminologies
- abbreviations
2. Disc specifications
- disc outline
- environmental conditions
- measuring conditions
- mechanical parameters
- optical parameters
- recorded parameters
- operation signals
3. Information Area Format
- track structure
- sector structure
- modulation method (8/16 Modulation)
- Lead-in, Middle and Lead-out Area
Structure of Video Book (Book B): File System Part
===============================================
1. General
- scope
- Normative Reference
- Definitions
- Notations
- Data types of descriptor field
2. Volume Structure
- Requirements for DVD-ROM disc
- Volume Space
- Volume Structure of UDF Bridge Format
- UDF Bridge Volume Recognition Sequence
- Anchor Point
- Volume Descriptor Sequence
- Logical Volume Integrity Sequence
- CD-ROM Volume Descriptor Set
3. File Structure
- Requirements for DVD-ROM disc
- UDF File Structure
- UDF File Set Descriptor Sequence
- UDF Directories
- ICB
- ISO 9660 Directory Structure and Path Table
Structure of Video Book (Book B): Application Part
===============================================
1. General
- Scope
- General Specifications of Presentation Data
- Normative Reference
2. Technical Elements
- Definitions
- Symbols
- Notations
- Terminology
- Abbreviations
3. Introduction
- Logical Structure of DVD Video
- Presentation Structure
- DVD System Model
4. Navigation Data Structure
- Video Manager Information (VMGI)
- Video Title Set Information (VTSI)
- Program Chain Information (PGCI)
- Presentation Control Information (PCI)
- Data Search Information (DSI)
- Navigation Commands and Navigation Parameters
5. Video Object (VOB)
- Contents of VOBs
- Pack
- Player Reference Model
- Presentation Data
==========================================================
APPLICATION
==========================================================
[Data provided by JVC and Thomson]
DVD Presentation Data (summary)
===============================
Type Count Representation
------------- --------------------- --------------------------
Video 1 stream only MPEG-1 or MPEG-2 Video
Audio maximum of 8 streams Linear PCM and/or:
Dolby AC-3 (NTSC)
MPEG audio (PAL)
Sub-picture max 32 streams Run-length encoded
with bitmap of 2 bits/pixel
(Specific) relation of other standards
======================================
Video ITU-T H.262/ISO-IEC 13818-2 (MPEG-2 Video)
ISO/IEC 11172-2 (MPEG-1 Video)
Audio ISO/IEC 13818-3 (MPEG-2 Audio)
ISO/IEC 11172-3 (MPEG-1 Audio)
Dolby AC-3 standard
System ITU-T H.222 / ISO/IEC 13818-1 (MPEG-2 Systems)
Program/PES stream only (no Transport streams)
Restriction on transfer rate
============================
max total of combined audio and video: 9.8 Mbit/sec
max sum of Elementary streams + systems overhead: 10.08 Mbit/sec.
Video Data Specifications
=========================
DVD adds many additional restrictions to the popular compliance
parameter sets of MPEG. One good example is the restriction
on the coded size of a picture: MPEG-2 Main Profile @ Main Level
allows any coded frame size between 16 and 720 pixels horizontally
and 16 and 576 pixels vertically. However, DVD restricts the
coded size to a very limited, but practical, subset.
In MPEG, audio can be coded at a sample rate of 32, 44.1 or 48 kHz.
In DVD, the rates of both Dolby AC-3 and MPEG audio are strictly 48 kHz.
MPEG is a generic representation meant for a wide variety of applications.
DVD has taken a practical subset to promote interoperability by
simplifying implementations and insuring features (such as random
accessibility).
Coded representation: MPEG-1 (SIF combo)
MPEG-2 (Main Profile @ Main Level)
Frame rate: 29.97 or 25 Hz
TV system: 525/60 or 625/50
Aspect ratio: 4:3 (all video formats)
16:9 (all formats except 352 pixels/line)
Display Mode: pan & scan, letterbox
User_data: closed caption
Coded frame sizes: 525/60: 720x480, 704x480, 352x480, 352x240
625/50: 720x576, 704x576, 352x576, 352x288
(MPEG-1 is allowed only in 352x240 or 352x288 res).
GOP size: max 36 fields or 18 frames (NTSC)
max 30 fields or 15 frames (PAL)
Maximum distance 3 (i.e. IBBPBBPBBP...)
between reference
frames
Buffer size: 1.8535008 Mbits (MPEG-2) max 327689 bits (MPEG-1)
Transfer method: VBR, CBR (MPEG-2), only CBR for MPEG-1
Maximum bitrate: 9.8 Mbit/sec
Low_delay NOT permitted !!!!
Notes [my reflections]:
- the frame rate is the intended display frame rate. The number of
coded frames in a sequence may vary due to 3:2 pulldown (the DVD MPEG
decoder performs this function). The permitted values in DVD are
more restrictive than MPEG-2 MP@ML which includes 23.976, 24, and
30 frames/sec rates.
- aspect ratio is the display aspect ratio. Only 16:9 and 4:3 are
permitted. Note: MP@ML's 2.21:1 is not included.
- MP@ML has no GOP size restriction. In fact, the GOP() is considered
to be an insignificant layer in MPEG-2. Instead the sequence()
layer serves as the most important boundary.
- The M<=3 (reference frame distance) restriction is additional over
MP@ML. This distance is arbitrary, in the general MPEG syntax
and currently defined Profiles and Levels combinations.
- The MPEG-1 and MPEG-2 vbv_buffer_size limits are the same as
MP@ML and Constrained Parameters Bitstreams, respectively.
- The maximum bitrate of 9.8 Mbit/sec is more restrictive than MP@ML's
15 Mbit/sec limit. However, the point of diminishing returns
(no visual difference between original video and compressed video)
is reached by 9 Mbit/sec anyway.
- user_data() fields in MPEG video picture headers contain closed
captioning (similar to Grand Alliance and DVB methods).
See this site for more information: http://www.atsc.org/
- For picture sizes, only a very limited set of coded dimensions are
legal.
- Variable bit rate is permitted only in MPEG-2 streams since the
VBV model in MPEG-2 has provisions for it.
- contrary to popular belief: all DVD players are required to
decode video streams up to 9.8 Mbit/sec for indefinite periods
of time. The popular average rate of 3.5 Mbit/sec or 4.7 Mbit/sec
is merely canonical figures. ALL DVD PLAYERS MUST SUSTAIN
A 9.8 MBIT/SEC VIDEO DECODE RATE!!!!!!!
MPEG Display Formats
====================
MPEG-2 video decoder chips have implemented pan & scan for a few
years already since it has been a requirement for cable TV
and direct broadcast satellite. The letterbox (vertical filter)
requirement is a relatively new addition. The DVD generation of
MPEG-2 video decoders will probably also perform sub-picture
reconstruction.
Display Aspect Ratio
4:3 16:9
4:3 No conversion horizontal filtering
Source accomplished by TV monitor.
Aspect
Ratio
16:9 letterbox No conversion
(vertical filter)
- or -
Pan & Scan
Note: Letterbox Conversion is a mandatory feature in the DVD Player !!!
Subpictures
===============================
- run-length compressed bitmaps that are overlayed ontop of the
MPEG reconstructed video.
- Applications include: Menus, sub-titles, karaoke, and simple animation.
- Pixels are divided into four types:
1. background 2. Foregound 3. Empahsis-1 4. Emphasis-2
- 4 colors out of 16 color palette (4 colors are determined once per PGC).
- 4 out of 16 contrast values
- up to a maximum of 32 sub-picture bitstreams. Each subpicture stream
could, for example, could contain text from a particular language.
- subpicture buffer size is restricted to 62 Kbytes. This means
a maximum of 62 KB per GOP/cell. 32 Kbytes of this is control data.
- Maximum number of bits per run-length coded line is 1440 bits.
- Display area maximum: 720x480 (525/60) and 720x576 (625/50)
- area, content, color, and contrast can be changed every video field
- Sub-Picture Display Control Sequences (SP_DCSQ) control the
presentation of Sub-pictures.
- Presentation effects include: scroll up/down, fade in/out, etc.
Structure of Sub-picture Decoding Unit (SPU):
[ SPUH ][ PXD ][ DCSQT ]
SPUH: Sub-picture Unit Header (size of SPU, start address of DCSQT)
PXD: Pixel Data (variable length run-length coded)
DCSQT: Display Control Sequence Table (one or more display control
command sequences).
DCSQT: [DCSQ 0][DCSQ 1][DCSQ 2] ... [DCSQ n]
DCSQ: [Start time] [ Pointer to next DCSQ] [Command Sequence]
Command Sequence: [DCC 0][DCC 1]... [DCC m]
Display Control Commands (DCC):
- Set start address in PXD
- Set colors
- Set contrast
- Set SP screen position
- Start/stop display
- Set CHG_COLCON areas.
VBI Decoding
============
The Vertical Blanking Interval (VBI) packet (multiplexed at the
Cell level along with Navigation, Video, and Audio packets) contains
information which is directly inserted into the reconstructed video
signal, sans level adjustments (16 levels into a, e.g. 256 level
video signal).
- only 1 VBI channel per program (sub-pictures have up to 32)
- Line range is from 10 to 23 NTSC and 6 to 23.5 for PAL.
- Separate palette (16 Y values, Cr=Cb=128) from subpictures.
- No highlight
- Restricted DCSQ command set
VBI information is losslessly represented as a waveform, and coded into
packets. A far more bandwidth efficient alternative is to transmit the
source character stream in the MPEG video user_data() field, and then have
the NTSC/PAL modulator chip create the VBI signal from the character
stream.
This brings our tally of closed caption representations to THREE ways!!
1. as packets of 16-level sampled VBI waveforms.
2. as user_data() character streams.
3. as rendered subpictures.
Picture Size Conversion
=======================
All DVD players are required to have built-in vertical filters
which scale a 16:9 coded video image onto a 4:3 display. This
player feature is needed since it is anticipated that a majority
of movies will be coded for the 16:9 aspect ratio, while at the same
time most TV displays (in the early years) will be 4:3.
525/60 (NTSC-rate display):
(Note: 480*(4/3)/(16/9) = 480*0.75 = 360)
_____________________
| 60 |
|---------------------|
| |
| 360 | 480 lines total
| |
|---------------------|
| 60 |
-----------------------
625/50 (PAL-rate display):
_____________________
| 72 |
|---------------------|
| |
| 432 | 576 lines total
| |
|---------------------|
| 72 |
-----------------------
A simple bi-linear vertical filter can be applied, yielding good
visual results. Here, two source samples (s[n],s[n+1]) are weighted by
simple complementary factors and added together to form the destination
sample value (d[m]). These weights are easily implemented with shifters.
For interlaced displays, vertical filtering occurs only within the same
field parity.
d[0] = (3/4)*s[0] + (1/4)*s[1]
d[1] = (1/2)*s[1] + (1/2)*s[2]
d[2] = (1/4)*s[2] + (3/4)*s[3]
Audio data specifications
=========================
Linear PCM Dolby AC-3 MPEG-2 audio
Sampling frequency 48 or 96 kHz 48 kHz 48 kHz
Number of bits per sample 16/20/24 compressed compressed
(16 bits) (16 bits)
Max transfer rate 6.144 Mbit/sec 448 kbits/sec 640 kbits/sec
Max Number of channels 8 5.1 5.1 or 7.1
NTSC PAL
Mandatory Dolby AC-3 MPEG-2 audio
and/or Linear PCM and/or Linear PCM
Optional MPEG-2 Audio Dolby AC-3
=============================================================
Philips' provided three practical scenarios for audio.
Case 1: One mono language channel to be mixed with the Center
multichannel set.
Use Channels kbits/sec
Multichannel music & effects 5.1 or 7.1 384
Mono English dialogue 1 64
Mono French dialogue 1 64
Mono German dialogue 1 64
Case 2: One of the stereo lingual signals mixed with the L & R
channel of the playback multichannel set.
Multichannel music & effects 5.1 or 7.1 384
Mono English dialogue 2 128
Mono French dialogue 2 128
Mono German dialogue 2 128
Case 3: One to be selected for playback.
Multichannel with English dialogue 5.1 or 7.1 384
Multichannel with French dialogue 5.1 or 7.1 384
Multichannel with German dialogue 5.1 or 7.1 384
Audio Signal Decoding System
=============================
General
=======
- up to a maximum of 8 audio streams can be multiplexed into the
same cell with a single video stream. Each stream for example is
designated for a particular language or special effects & music
tracks.
- Dolby AC-3 used mandatory for 525/60 (NTSC) players and
MPEG-2 is mandatory for 625/50 (PAL) players, but optional
on discs themselves.
- LPCM (Linear Pulse Code Modulated) is mandatory for all players,
but optional on discs themselves.
- 48 kHz and 96 kHz uncompressed PCM audio
- High Definition Audio Experience
- A 525/60 disc must contain either Dolby AC-3 or LPCM.
A 625/50 disc must contain either MPEG-2 audio or LPCM.
Due to bandwidth efficiency, most titles will use the more
compact Dolby AC-3 or MPEG-2 audio.
- Extendibility is reserved for new algorithms such as
DTS, Sony SDDS, et al.
- IEC-958 Digital Audio Interface for external decoder/receiver.
Output types: compressed AC-3 or MPEG stream, two channel LPCM.
DVD players are required only to output a full reconstruction
of the Left and Right channels. An external AC-3 decoder
would optionally decode all 5.1 channels. A more expensive
DVD player would output all 5.1 reconstructed channels.
Dolby AC-3 parameters
====================
Sampling frequency: 48 kHz
bitrate: 64 kbits/sec to 448 kbits/sec per stream
Audio coding mode 1/0, 2/0, 3/0, 2/1, 2/2, 3/1, and 3/2 (acmod)
Characteristics: - dialog normalization
- dynamic range compression
- downmixing (5.1 -> 2 channel) capability
- Dolby Pro-Logic Encoding (5.1 -> 2 channel)
- Karaoke mode (voice overlay)
MPEG Audio parameters
=====================
Sampling frequency: 48 kHz only
MPEG-1: Layer II only
Mono (32 to 192 kb/s) and Stereo (64 to 384 kb/s)
MPEG-2: - main stream (same as MPEG-1)
- extension stream (up to 528 kbit/sec)
- sum of main and extension stream up to 912 kb/s
- unmatrix mode excluded (always MPEG-1 compatible)
LPCM Coding
===========
- Lossless/uncompressed PCM audio
- Sampling frequency: either 48 kHz or 96 kHz
- bits/sample: 16, 20, or 24 bits
- up to 8 PCM channels.
Due to the user rate bandwidth limitation of 6.144 Mbit/sec for
LPCM audio, not all combinations of channel count, sample precision
and sample rates are permitted:
Sample Sample Channel Count
Rate Prec.
48 kHz Mono 2 CH 5 CH 8 CH
16 Yes Yes Yes Yes
20 Yes Yes Yes No
24 Yes Yes Yes No
96 kHz
16 Yes Yes No No
20 Yes Yes No No
24 Yes Yes No No
===============================================================
[data from Mitsubishi]
DVD Feature Functions
=====================
1. Multiple titles on one disc
2. Seamless playback transitions
2.1 multiple versions of language credits
2.2 director's cut (Parental lock)
2.3 multiple version based on camera angles
3. Multi-Language System (audio, closed caption, et al)
4. Navigation System
5. Multi Screen Aspect Ratio (16:9, 4:3, letterboxed, pan&scan)
6. Multi Sound system (5.1 or 7.1 channels)
maximum program_mux_rate: 10.08 Mbit/sec
Audio streams are multiplexed with video. So, alternative
audio tracts beyond the limitation of 8 must be multiplexed
with a different video stream.
Source: Pioneer
Title: Interactive functions
==============================
Basic User interface:
- Control: ten keys and cursor keys
- Display: menu graphics and high-light
GUI Display:
- Menu picture with subpicture and MPEG graphics
- highlighted area
Menu:
Basic
1. Title A
2. Title B
3. Title C
4. Previous 5. next
Multi-page Menu
1. Title A 4. Title D 7. Title G
2. Title B 5. Title E 8. Title H
3. Title C 6. Title F 9. Title I
Exit Next Prev Exit Next Prev Exit
Interactivity
=============
Level of functionality
1. simply play
2. interactivity similar to Video-CD
3. Interactivity simular to PC Applications
Functions
=========
Information Control
- parental control
- copy management
Menu
- Title: sub-picture
- Root: Angle
- Audio: part of title
Search functions:
- program search
- time search
- angle search
- part of title search
Seamless play function
Still picture function
File Structure Hierarchy
=========================
The DVD is broken into two separate types of information:
Navigation Data (control) and Presentation (object) data.
Control data acts as pointers (like an operating system's File
Allocation Table) to the actual video and audio object data on
the disc.
Control data can be expressed as a series of nested layers:
Title distinguishes multiple movies or TV episodes
on one disc. Each title is one of two types:
a single program chain (One_Sequential_PGC_Title)
or a collection of different program chains
(Multi_PGC_Title).
Program Chain A collection of programs with a particular theme
in common.
Part_of_Title Links to one or more Program (PG) units on the disc.
Like PGC, this mechanism can be used to create different
versions (camera angle, ratings, outcomes, etc.) of
the same program chain. POTs can also be used to mark
scenes.
Program Usually a scene. Consists of multiple cells.
Cell Preceded by a navigation packet, and alternating
video and audio packets. A cell is typically all
the video and audio data associated with an integer
number of a group of pictures.
VOBU Video Object Unit: "typically" a group of pictures (GOP)
GOP 1. smallest granularity of random access on disc
(Group of pictures being with a coded Intra frame)
2. largest interframe dependent coding unit.
(Interframe compression is bounded within a GOP)
Usually 15 coded frames of data (0.5 seconds display
duration).
Packet DVD packets are 2048 bytes (sector payload size) large.
As per MPEG-2 PES/Program streams, they contain data
from only one data type (video, audio, etc.)
NAV packet contains the optional Buttom-Command defining the
playback behaviour of the cell.
1. Logical structure of Video Manager and Video Title Set
[notes from Hitachi]
=========================================================
A DVD may contain up to 99 different titles, each with an initial
Navigation Menu allowing the user to select among different versions
of the title. The root menu which branches to all titles on the
disc originates with the Video Manager. Each title is organized as a
Video Tile Set (VTS).
DVD: [VM][VTS #1][VTS #2] ..... [VTS #n] where n<=99
The VM's VMGI includes: Attributes for the Menu, Tile Search Pointers,
and the PCGI for the Menu.
VM: [VMGI][VOBS for Menu][Back up for VMGI]
The Control Data (VTSI) for the title (VTS) includes: attributes for Menu,
Attributes for Title, Part of Title Search Pointer, Time Map Table,
PGCI for Menu, and PGCI for Title. The Video Objects (VOBS) contain
the actual program chains, Part_of_Tiles, programs, and so forth.
VTS: [VTSI][VOBS for Menu][VOBS for Title][Back up for VTSI]
Legend:
VM Video Manager: sets up menus for a series of titles (1 through n)
VTS Video Tile Set: a collection of video objects.
VMGI Video Manager Information:
VOBS Video Object Set
PGCI Program Chain Information
Structure of Title
==================
A title begins with the entry program chain (Entry PGC).
It can branch to a single program chain (One_Sequential_PGC_Title)
or multiple program chains (Multi_PGC_Title). The location
of the branch is determined by the link condition.
Structure of a Program Chain (PGC)
==================================
The program chain is broken into two separate entities:
- program control information (PGCI)
- video object (VOB)
The PGCI defines the playback order of Programs by acting as
a table of addresses which point to the sector locations of
the program cells on the DVD. A program cell is essentially a
group of pictures (GOP), spanning multiple sectors, and contains
the actual interleaved packets of compressed bits for video and
audio data.
Part_of_Title (PTT)
===================
The Part_of_Title divides a title in a maximum of 99 different pieces.
The intent of the PTT is aid in the construction of multiple versions
of the same title.
One_Sequential_PCG_Title: The Part_of_Title and Program numbers
are synchronized.
[ PTT #1 | PTT #2 | .... | PTT #n ] Part_of_Title
[ [PG #1] | [PG #2] | .... | [PG #n] ] Program Chain (PGC)
Multi_PGC_Title:
branch PTT #2
--> [PG #1] (PGC1)
PTT #3 PTT #m
PTT #1 --> [PG #1] [PG #j] ... [PG #k] (PGC2)
[PG #1]
--> [PG #1] (PGC3)
Presentation of PGC
===================
The program chain (PGC) can be presented either serially (linear)
or in random/shuffle (non-linear) fashion.
For example, a quiz title should break each question into separate
programmes. The next program chain branched to would be determined by
the answered provided by the user.
Still
=====
Still pictures are coded as MPEG intra frames. They may be
displayed for indefinite duration. They can be accompanied
by background music, or total audio mute.
- still function is created by the action of the navigation system
- The same video frame and sub-picture is frozen (displayed over
and over again on the TV) while audio is or playing in background.
There are three types of the Still Function:
Type Timing Still time in seconds
PGC Still Stills at end of the PGC 0-254, limitless
Cell Still Stills at end of the Cell 0-254, limitless
VOBU Still Stills in every VOBU in the Cell limitless
VOBU: Video Object Unit.
Search Functions by User
========================
There are 6 search functions defined for DVD. Two are present
in most of today's VCRs: the linear style Time Search and Scan
(Fast forward, rewind). The other 4 are made possible thanks to
the non-linear, random-access playback capability of DVD.
User operation (ability to scan through or play) can be prohibited by
content, identified by such attributes as the parental control level.
For example, certain Part_of_Title's can be skipped over which contain
R-rated (US) scenes.
Title User can select the exact title to shuttle to.
Search:
Part_of_Title User can go to specific version (PG-13, R,
Search: directors cut, children's version) or camera angle
by either title name or number.
Program User can go to a specific scene (car chase, opening
Search: credits, gun fight, etc.) within a program chain.
Time User can go to a specific SMPTE style time code
Search: (HH:MM:SS:FF) location within a program chain.
Scan: Scan (linearly) forward or backwards in time.
GoUp: Within the current program chain, jump to the next
program chain. This command traverses the DVD control
information hierarchy.
For Time Searches, all DVD players are required to arrive
to the nearest I picture. It is optional that DVD players
be capable of arriving at the exact picture (regardless of
its picturing coding type).
Navigation Commands and Parameters
==================================
The author (content provider) is given the freedom of creating an
arbitrary branching structure for a given title. Of course some restraint
should be exercised since, thanks to interframe MPEG coding dependencies
and physical servo mechanism limitations, a program chain cannot be
constructed of 30 pictures/sec of totally randomly located information
on the disc.
However, the constant DVD transfer rate of 11 Mbit/sec provides
some flexibility when the average program rate is kept lower.
For example, if the average bit rate is only 5 Mbit/sec, then
the player can waste 6 Mbit/sec of potential transfer rate
in random access overhead.
Player Settings:
There are 24 system parameters for player setting:
SPRM Meaning
---- -----------------------------------------------------------------
0 Menu Description Language Code
1 Audio stream number
2 Sub-picture Stream number
3 Angle Number
4 Title Number
5 VTS title Number
6 Title PGC Number
7 Part of title number for one sequential_PGC_Title
8 Highlighed Buttom number
9 Navigation Timer
10 Title PGC number for Navigation Timer
11 Audio Mixing Mode for Karaoke
12 Country Code for Parental Management
13 Parental Level
14 Player Configuration for Video
15 Player Configuration for Audio
16 Initial Language Code for Audio
17 Initial Language Code for Sub-picture
18 Initial Language Code Extension for Sub-picture
19 Initial Language Code for Sub-picture
20 Reserved
21 Reserved
22 Reserved
23 Reserved
General Parameters:
Used for interactive operation of titles, such as quizzes, or
games.
- 16 general parameters for navigation. These are RAM variables
in the DVD players for use as, e.g., arithmetic scratch pads,
counters, etc.
- Arithmetical operations are available (add, compare, etc.)
Navigation Commands
===================
- Each command consists of a single instruction or a combination of
two or three instructions.
Instruction Groups:
Goto branch between command
Link transfer between same Domain
Jump transfer between each Domain
Compare recognition of parameter value
SetSystem player system setting
Set calculate GPRM values
Location of each command
========================
Within a program chain (PGC), commands can be located at the
front of the chain, in between cells of the chain, and at the
end of the chain.
Program chain
[Pre-Commands] [Cell] [Cell] [Cell-Command] [Cell] [Post-Commands]
Each cell can have one command. There is a restriction that
no more than 128 commands can be contained within a program chain:
Pre-commands + Cell Commands + Post Commands <= 128
Further, there are a maximum of 36 buttons, each of which can
have one associated command.
Example of a PGC transition
===========================
[taken from the Hitachi overheads]
3 quiz problems are presented to the user. Each quiz problem/question
is coded as a separate program chain. One of the questions prompts
the user for a "Yes" or "No" answer.
The Link command is used to branch from the original top-level menu
to one of the three program chains. The Set Command is used to
tally a score. Finally, the CompareLink command (which consist of
two commands, Compare & Link) branches to a particular Program depending
on the user's answer.
==========================================================
FILE SYSTEM
==========================================================
Directory Structure
===================
File directory is based on ISO 9660 and the micro Universal
Disk Format Specification (M-UDF).
The latest UDF specification (November 3, 1995) can be obtained from:
Optical Storage Technology Association
311 East Carrillo Street
Santa Barbara, CA 93101
USA
Voice: +1 805 963 3853
Fax: +1 805 962 1541
E-mail: osta@aol.com
Root ---------------------------------------------------
| | |
Video_TS Audio_TS Provider defined
|
|
|
| - Video_TS.INF (Video Manager Information)
| - Video_TS.VOB (Video Manager Menu)
| - Video_TS.BUP (Video Manager Information)
|
| - TITLE_A.INF (Video Title Set Information)
| - TITLE_A0.INF (Video Title Set Menu)
| - TITLE_A1.VOB (Video Title Set Title)
| - TITLE_A2.VOB (Video Title Set Title)
| - TITLE_A.BUP (Video Title Set Information)
Layout of Volume
================
Lead-in Data Recorded Area Lead Out
ISO9660&M-UDF
File 0
File 1
Disc Type and Capacity
======================
Single layer Dual layer Single layer Dual Layer
Single sided Single sided Double sided Double sided
12 cm 4.7 8.5 9.4 17
8 cm 1.4 2.6 2.9 5.3
Recordable time on a disc scenarios:
====================================
Avg. Minutes
rate SL/SS DL/SS SL/DS DL/DS
Movie
4.8 130 236 259 472
Video 3.5
Audio (AC-3 3 lang)
Sub-picture 4
Karaoke 4.0 155 282 310 564
Video 3.5
Audio (AC-3 1 lang)
Sub-picture 1
Video Clip A 5.2 120 218 340 436
Video 3.5
Audio (2 ch. PCM)
Sub-picture
Video Clip B 8.8 71 129 142 258
Video 7.0
Audio (2 ch. PCM)
Sub-picture
Video Clip C 8.4 75 136 149 272
Video 3.5
Audio
Sub-picture
==========================================================
PHYSICAL
==========================================================
Physical specifications:
===============================================
Toshiba provided the following table:
12 cm disc 8 cm disc
User Data Capacity Single Layer 4.7 GByte 1.4 GByte
Dual Layer 8.5 GByte 2.6 GByte
Pit Length (minimum) 0.4 microns
Track pitch 0.74 microns
recording modulation 8/16
sector size 2048 bytes
error correction reed-soloman product code:
code RS(208,192,17) x RS (182, 172, 11)
ECC Constraint 16 Sectors (=32 Kbytes)
Length
Further physical specs
======================
Spiral direction clockwise
Comparing DVD and CD
[Mitsubishi data]
=================================================
Units DVD CD
Outer diameter millimeters 120 120
Thickness of substrate millimeters 0.6 1.2
track pitch microns 0.74 1.6
min. pit length microns 0.40 SL 0.834 - 0.97
0.44 DL
wavelength nanometers 650 780
Numerical Aperture of N/A 0.60 0.45
Objective Lens
Error correction N/A RS Product RS 8-bit code
Code
Error correction percentage 13 25
overhead
Data capacity Gigabytes 4.7, 8.5, 0.65 (CD-ROM)
9.4, or 17 0.80 (CD Music)
Channel modulation N/A 8/16 8/17
Data bit rate (1X) Mbit/sec 11.08 1.44
Reference scanning meters/sec 3.49 SL, 1.2 to 1.4
velocity 3.84 DL
Reflectivity percentage 70 min SL 70 min
25 to 40 DL
Thickness of spacing microns 40 - 70 N/A
Layer in Dual Layer
Spot Size lambda/NA 0.63 1
Focus Depth lambda/NA^2 0.47 1
(Focus Margin)
Comatic Aberration lambda/NA^3 0.35 1
(Title margin)
Spherical Aberration lambda/NA^4 0.26 1
(Thickness Tolerance)
Note: the minimum pit length for Double layer is 10% greater, hence
the 10% less dense figure for Dual layer discs.
more Toshiba data...
Disc specifications:
===============================================
8 cm 12 cm
outer diameter: 80 mm 120 mm
outer data diameter: 76 mm 116 mm
inner data diameter: 48 mm 48 mm
Track pitch: 0.74 microns (same as Toshiba original proposal)
Pit length: Min: 0.4 micron (same as Toshiba original proposal)
Max: 2.13 micron to 1.87 micron
Scanning velocity: 3.49 m/sec
Channel bitrate: 26.16 Mbit/sec
User data bit rate: 11.08 Mbit/sec
Recording order on the disc (Track Structure)
===============================================
Legend:
I Lead-in area (leader space near edge of disc)
D Data area (contains actual data)
O Lead-out area (leader space near edge of disc)
X un-usable area (edge or donut hole)
M Middle area (interlayer lead-in/out)
B Dummy bonded layer (to make disc 1.2 mm thick instead of 0.6mm)
Single layer disc:
direction: continuous spiral from inside to outside of disc.
| ----------------------->
|BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB outer edge
|XXIIIDDDDDDDDDDDDDDDDDDDDDOOOXX of disc
|
reference
axis
Dual layer disc:
(A) Parallel track path (for computer CD-ROM use)
Direction: same for both layers.
----------------------->
XXIIIDDDDDDDDDDDDDDDDDDDDDOOOXX Layer 1
XXIIIDDDDDDDDDDDDDDDDDDDDDOOOXX Layer 0
----------------------->
(B) Opposite track path (for movies)
Direction: opposite directions
Since the reference beam and angular velocities are the same
at the layer transition point, the delay comes from refocusing.
This permits seamless transition for movie playback.
<----------------------
XXOOOODDDDDDDDDDDDDDDDDDDDDMMMXX Layer 1
XXIIDDDDDDDDDDDDDDDDDDDDDDDMMMXX Layer 0
----------------------->
Data Sector Configuration
=========================
>>From the original Toshiba DVD proposal (circa Spring 1995), the
following three items changed:
- sector information in ID
- EDC Generation Method
- Initial Value of Main Data Scrambling
The 2064 byte sector is, for purposes of error correction, organized
into 12 separate rows, each with 172 bytes. The first row starts
with the 12 Byte sector header (ID, IEC, Reserved bytes), followed
by the remaining data bytes. The following 10 rows contain only
data. The final row is punctuated with a 4 Byte field (EDC).
Row Fields within row
--- ----------------------------------------------------------------------
0 ID (4B) IEC (2B) RESERVED (6B) Main data (160 Bytes: D[0] - D[159])
1 Main Data (172 Bytes: D[ 160] - D[ 331])
2 Main Data (172 Bytes: D[ 332] - D[ 503])
3 Main Data (172 Bytes: D[ 504] - D[ 675])
4 Main Data (172 Bytes: D[ 676] - D[ 847])
5 Main Data (172 Bytes: D[ 848] - D[1019])
6 Main Data (172 Bytes: D[1020] - D[1191])
7 Main Data (172 Bytes: D[1192] - D[1363])
8 Main Data (172 Bytes: D[1364] - D[1535])
9 Main Data (172 Bytes: D[1536] - D[1707])
10 Main Data (172 Bytes: D[1708] - D[1879])
11 Main Data (172 Bytes: D[1880] - D[2047]) EDC (4B)
ID: Identification Data (32-bit sector number)
IEC: ID Error Correction
EDC: Error Detection Code
EEC Block Configuration
=======================
To combat bursty errors characteristic of CD-ROM, 16 sectors are
further interleaved together, forming a block of 192 rows
(16 sectors * 12 rows/sector = 192 rows). Error correction bytes
are concatenated to the data block in a 2-dimensional fashion
(hence the term "product" in the phrase "Reed-Soloman product codes").
Specifically: at the end of each row, 10 bytes of RS data is added
(hence the RS(182,172,11) vector. At the end of the block, 16 rows
of RS data is added (hence the RS(208,192,17) vector). Therefore
out of 37,856 total bytes (182*208) for the interleaved block of
data, 33,024 bytes (192*172) or roughly 87% is payload.
<----- data block -----------> <---------- P1 -------------->
D B[ 0][ 0] ... B[ 0][171] | B[ 0][172] .... B[ 0][181]
a B[ 1][ 0] ... B[ 1][171] | B[ 1][172] .... B[ 1][181]
t . |
a . |
. |
B[190][ 0] ... B[190][171] | B[190][172] .... B[190][181]
B[191][ 0] ... B[191][171] | B[191][172] .... B[191][181]
--------------------------------------------------------------
B[192][ 0] ... B[192][171] | B[192][172] .... B[192][181]
.
P .
0 .
B[207][ 0] ... B[207][171] | B[207][172] .... B[207][181]
P0: RS(182, 172, 11)
P1: RS(208, 192, 17)
8/16 Modulation
===============
The lowest layer of the communications channel is the 8/16
channel code, which helps reduce DC energy and lower the SNR
threshold for the pickup signal. Although half the channel rate
is doubled thanks to the 8/16 code, the overall user throughput
for the desired uncorrected rate of 1x10^-3 is greater because of
it. The advantage of the 8/16 code is:
- Small DC component (no long run lengths of 1's or 0's)
- Applicable RAM
- Simple decoding circuits
>>From 16 channel bits, 8 user data bits are produced.
=============================================================
Source: Nimbus
Title: Disc Manufacturing Technology and Equipment
DVD Laser Beam Recorder
- with respect to CD, DVD only requires changes to recorder mask.
- Ultra violet laser, argon ion
- Wavelength of 351 nanometres
- c.5000 hours lifetime
- final objective lens, n.a. 0.9
- secondary focusing
- aperture for CD mastering
- spot beam focus checker is mot critical part.
- yield rate for DVD (SS/SL): 90%
Operation in DVD or CD mode
- Identical glass preparation and chemicals
- universal lenses
- switchable aperture
- secondary focusing
- elliptical spot for CD mastering
Elliptical spot:
- reduces resolution across track
- maintains DVD resolution along track to improve control of pit ends.
Production:
- 200 - 300 master titles per month
- 1.2 - 1.5 million stamped discs per month
=======================================================
Notes from Hitachi
Flow of Data in player:
Stage 1: SYNC detection, 8/16 Demodulation, ID Detection
A total of 8 sync codes are inserted into the 8/16 modulated
channel bitstream representing the current physical sector.
Sync code words are unique in the 8/16 code table (so they
cannot be generated by the 8-to-16 mapping).
Detection looks for sync codes in order to determine where
sectors begin and end. Here the channel bit rate input to this
block is 26.16 Mbits/sec, and output is 13 Mbit/sec.
Stage 2: Error detection and correction
If the check bits (EDC) don't match the fingerprint of
the unscrambled data, the Reed Soloman bytes (IEC) are used to
attempt error correction of the corrupted data. Here the
channel rate output by this block is 11 Mbit/sec (2 Mbit/sec
of error correction parity data, IEC, has been stripped).
Stage 3: Descramble
Data on the disc is descrambled for purposes of
copy protection.
Stage 4: EDC Check
The fingerprint of the unscrambled data is checked
against the EDC code to verify whether the data was
correctly descrambled.
Stage 5: Track buffer
This FIFO maps the constant user data bit rate of 11.08 Mbit/sec
to the variable bit rate (Max mux rate 10.08 Mbit/sec) of the
program streams.
Stage 6: Transfer to MPEG system decoder.
Track Buffer
============
The size of the track buffer is left to the implementation, although
the minimum recommended size is 2 Mbit. This is computed as:
B > Tmax * VBRmax = 0.104 sec * 10.08 Mbit/sec
Tmax is the maximum latency of one disc revolution, and VBRmax
is the maximum mux rate for any Program.
In some systems, the Track Buffer and the MPEG STD/VBV (System
Target Decoder/Video Buffer Verifier) are combined.
Seamless playback illustration
==============================
Input stream to Track Buffer:
Time
----> n: sector number
|<------- T --------->|
[n-3][n-2][n-1][ n] ... track jump ... [m ][m+1][m+2][m+3][etc.]
(no data transfer during
discontinuity)
Corresponding output from Track Buffer:
Initial buffer
delay introduced by track buffer
|<--------->|
[n-3][n-2][n-1][ n][m ][m+1][m+2][m+3][etc.]
^^
no apparent discontinuity
from perspective of MPEG Systems
decoder.
The memory size needed for seamless playback control can be
computed as:
T * VBR = 0.25 seconds * 8 Mbit/sec = 2 Mbits
This is of course implementation-dependent. T here is the
maximum jump distance (10,000 sectors).
Labeling information [from Warner Advanced Media Operations]
=================================================================
Labeling can be similar to standard CD labels
or one of three new types:
- Reverse Printing: underside of blank 0.6mm clear substrate
provides unique wet look and additional protection
- Mastered in Graphics: by transferring images directly to the
glass master ensuring 100% yield.
- Laser Scribed Titles: on stampers, Image added right at press.
DVD Doubled Sided Disc Label solution:
- the inner radius of DVD is smaller than regular CD's (to
improve areal utilization of disc, hence capacity). This
favors the outer edge.
- labels are printed along outer 5mm edge of disc.
Label Angular arc size
-------------------------- --------------------
Movie Title Information: 217 degrees
Disc ID Code: 57 degrees
Side: 25 degrees
Company: 29 degrees
Gaps between above labels: 8 degrees x 4 gaps
==========================================================
Hollywood Panel Discussion
==========================================================
Executive leaders from the home video branches of MGM, MCA, Warner,
Columbia, Turner (New Line Cinema) and Tri-Star were present.
The three primary issues for them are:
1. Availability of Software: getting titles mastered and pressed
to entice people to buy DVD players. Most executives on the
panel felt that new titles should be in the $20 range, and
that "fully amortized" titles (read: talent already received and
spent their money) will allow studios to resell their vast libraries.
Only one executive felt his studio will market new titles at higher
prices----in the $60 range. These older libraries will be priced
lower ($10 ?) in order to attract hardware purchases. The idea
is to convince DVD owners to own their own libraries rather than rent.
2. Timing of releases around world: studios feel they do not want
American titles to be played on European players since the
release dates of video (and cinema for that matter) differ around
the world for political and logistical (seasons, holidays) reasons.
Region Codes would become the mechanism.
3. Copy protection: studios feel that closure on this heated issue is
expected within weeks.
- currently only Disney, Paramount (Blockbuster), and Fox have yet
to announce DVD policies.
- It is hoped that DVD will simulate the US music video market, where
VHS has clearly proven not to be the format.
-----
End of notes
cfogg@chromatic.com
Philip Nemec / SGI / nemec@sgi.com