1. Main features
(Source:
Philips) Super
VCD (SVCD) standard is set by the China National Committee of Standards &
Philips, Sony, Matsushita and JVC. It is based on MPEG-2 technology with variable
bit rate (VBR) support. SVCD can deliver up to 2 times sharper video images
than the previous VCD standard. SVCD specifies MPEG2 video at 576x480 resolution,
almost four times the MPEG1 resolution specified in VCD.
SVCD
is backward compatible with VCD1.1, 2.0, and Interactive VCD 3.0 formats. Furthermore,
while VCD requires text to be embedded in the video, SVCD uses a dedicated text
data stream. This allows graphics and text such as multi-language subtitles
for movies or karaoke text to be added at any time, while eliminating artifacts
common with the compressed graphics and text streams of VCD.
Why should i care about it ?
There is a market need for a standardized full digital Compact
Disc based video reproduction system. The standard has been specified to allow
for cost optimized Super Video CD players. The Super Video-CD standard upgrades
the current Video-CD format. It utilizes better Video and Audio Quality. It
also standard includes extensions for surround sound multi-channel audio, provisions
for PC playback, and is prepared for further future improvements. It is also
based on variable bit rate (VBR) MPEG2 coding for more efficient use of the
disc capacity. The playing time per disc can vary from 35 minutes to more than
70 minutes depending on the average bit rate used. The objective of the new
standard is to ensure the best price/ performance combination possible with
the latest state of the art technology available, and to offer more flexibility
for publishers to use the best video/audio quality given its limited bandwidth
and disc capacity.
In conclusion you can have:
- Flexibility to use the best Video and Audio quality given the limited disc
capacity.
- Best price/performance combination.
- Utilizing low cost CD duplication technique.
- Make use of the installed gear of CD recorders.
Hey..How is Super VideoCD compared with DVD?
- Similar Audio and Video quality Same MPEG2 technology
- Super Video CD has lower cost Normal CD mastering and duplication
- Super Video CD authoring much easier Desktop PC systems with CD recorder
- Simplified Licensing
- Super Video CD has less playing time
Which are the Super VideoCD main features ?
- Resolution: 480x576 (PAL) / 480x480 (NTSC) (2/3 resolution
of D1, better as regular TV)
- Video : MPEG2 VBR, average bitrate up to 2.6 mbps
- Still picture resolutions up to 704 x 576
- Graphic overlay in separate video plane
- 4 selectable subtitles for Movies or lyrics for Karaoke
- Audio : Variable audio bitrate, 32 kbs to 384 kbs allowing (5.1) MPEG2 Multi-channel
- Dual audio streams for multi-lingual sound
- Extended interactivity : Player control API, variables, conditional instructions
Where it now used (or will) ?
(western world)
- Movie applications. Only for prototyping, testing and low volume duplication.
- Non movie applications : Educational, point of purchase, site based advertising,
cover mount, personal video, photos and soon video.
(Far-East)
- Movie distribution
- Karaoke
- Educational applications
What are the improvements over the VideoCD v2.0?
Variable bitrate (VBR)
|
MPEG-2 Video
|
Two Audio streams
|
Surround Sound Multi-channel Audio
|
Overlay Graphics
|
The variable bit rate ( VBR ) may vary
up to double (2X) speed. For a 2 disc movie title of 110 minutes, the
gain of the average bit rate of the MPEG video stream is typically 45%,
which is used for the resolution improvement.
|
Much better picture quality is achieved
by using MPEG-2 instead of MPEG-1 coding, and by interlaced double vertical
resolution of 480 lines for NTSC and 576 lines for PAL.
|
One extra MPEG audio stream has been
added for a second language. The Audio streams are selectable by the
user, and VBR coding is used for a more efficient compression.
|
As backward compatible extension in included
Movie surround sound MPEG-2 Multi-Channel (5+1 channels ) coding.
|
New Overlay Graphics for Movie sub-titling
and Karaoke lyrics, with up to four selectable (language / lyrics) sub-channels,
and Karaoke highlight color change support.
|
OK..now give me a roundup between SuperVCD vs. VCD
Item
|
Super Video CD
|
Video CD 2.0
|
Sector rate
|
variable up to 150 Hz
( 2X speed )
|
fixed to 75 Hz
|
CDDA tracks
|
not used
|
optional
|
Data retrieval
File locations
|
Fixed locations
|
Fixed locations
|
CDI sub-directory
|
not used
|
mandatory
|
Video
bit rate (mbps)
resolution NTSC (HxV)
resolution PAL (HxV)
|
Mpeg-2
variable to 2.6
480x480
480x576
|
Mpeg-1
1.15
352 x 240
352 x 288
|
Still Picture
resolution NTSC (HxV)
resolution PAL (HxV)
|
Mpeg-2
480 x 480,704 x 480
480 x 576, 704 x 576
|
Mpeg-1
352 x 240, 704 x 480
352 x 288, 704 x 576
|
Audio
bit rate
audio channels
surround sound
|
MPEG-1, layer II
from 32 to 384 kbps
up to 2 stereo or 4 mono
MPEG-2 (5+1) extension
|
MPEG-1, layer II
fixed to 224 kbps
1 stereo or 2 mono
stereo with Dolby pro-logic
|
Overlay Graphics and text
sub-channels
coding
|
overlay video plane
<= 4
4 color CLUT ( 2bit / pixel )
|
not used
N/A
N/A
|
Where i can play it?
The Super Video CD is based on the CD-ROM-XA format. This format allows the
possibility to add PC playback applications on the same disc enabling the disc
to be played on a PC. The "EXT" directory is mentioned to contain
such application and setup files. The main root could contain even an autorun
enabling files.
So in other words you can play it into :
- TV based systems
- DVD players (New DVD players will soon (Q3, 1999) have Super Video CD playback
including CD-R capability)
- Super VideoCD players (can also play Mp3
CDs or serve as a WevTV
bronswer)
- PC based systems.
2. Disc structure
SVCD Disc Structure
- Page 2
(Source
: Philips)
How is the SVCD disc structure?
The
Disc format is compliant with CD-ROM XA, and can be a pre-mastered disc or a
CD-Recordable disc. All tracks of the Program Area are encoded as CD-ROM XA
data tracks. The first track on the disc is a special DATA track with data retrieval
information and interactive playback MPEG sequences. The MPEG-2 streams on disc
are recorded in MPEG tracks, and are intended to be played sequentially starting
from Track #2 . A Karaoke / Music application has normally one track per song.
This means that song number 1 is recorded in Track #2, and song number 2 in
Track #3, and so on. A Movie could have different coded parts of INTRO, COPYRIGHT,
FILM, CREDITS, each stored in a separate track. The film itself can be stored
in one track with the possibility to be subdivided into chapters within the
one track.
DATA track format
The DATA track contains Special Information Areas, and a Segment Play Item Area
intended for menus or interactive use, and other optional program data files.
Data files use Mode2, Form1 ( 2048 byte ) DATA sectors, and MPEG files use Mode2,
Form2 (2324 byte ) MPEG sectors.
Karaoke Basic Information Area
A Super Video CD disc can contain the Karaoke Basic Information Area as
an option. The data in the Karaoke Basic Information Area provides basic information
to produce a quick reference table of the Karaoke music programs on the disc.
Information Area
The Super Video CD Information Area contains the files "INFO.VCD"
and "ENTRIES.VCD", "TRACKS.SVD" and "SEARCH.DAT".
As an option it may contain the files "LOT.VCD" and "PSD.VCD".
Segment Play Item Area
A Segment Play Item consists of a MPEG-2 Program Stream (PS) stored in MPEG
sectors. It may contain video, audio and still pictures conform to MPEG 2 Program
Stream coding. The Segment Play Item Area address is indicated in "INFO.VCD".
Segment Play Items may occupy one or more segments. Segment Play Items are not
accessed directly by the normal track playing mechanism, but indirectly by interpretation
of the Play Sequence Descriptor file.
MPEG track format
All Tracks except the first Track should be MPEG tracks. Each MPEG track
must contain only one MPEG-2 Program Stream, stored in MPEG sectors, using Mode2
Form2 with 2324 user bytes.
File system structure
A Super Video CD disc contains two different Data Retrieval Structures; The
first is the File System structure conform to CD-ROM XA, and ISO 9660, and a
second Data Retrieval Structure is based on absolute sector addresses to the
specific SVCD files.
Directory structure
The required directories for a Super Video CD disc are: Root directory 0,
"SVCD", "MPEG-2", and "EXT" directories. If Karaoke
Basic Information is available on a disc, then these files must be located in
the directory "KARAOKE". The SVCD Information files must be located
in the directory "SVCD". If the Segment Play Items are available on
the disc then these files must be located in the directory "SEGMENT".
All files that represent the MPEG Audio/Video Tracks must be
located in the directory "MPEG2". The "SCANDATA.DAT" file
must be located in the "EXT" directory. Other files or directories
may exist outside the required Super Video CD directory. The figure below gives
an example of the file structure for a Super VideoCD disc. Additional files
can exist within the directories shown.
SVCD directory
This directory contains the files from the Super Video CD Information Area.
The required mandatory files in the SVCD directory are "INFO.VCD"
, "ENTRIES.VCD", SEARCH.DAT and TRACKS.SVD. Optional files in the
SVCD directory are "PSD.VCD" and "LOT.VCD".
INFO.VCD file
This file of one sector contains the Super Video CD system identification
and a provision to identify the discs belonging to one Album. An Album
is a series of discs which contain related Audio/Video programs. It also contains
information associated with the Play Sequence Descriptor ( PSD ).
ENTRIES.VCD file
This file of one Sector contains the list of start positions of Entries
in the MPEG-2 Audio/Video Tracks on the disc. The Entry address values are used
by the PSD playlist to access Play segments in the MPEG tracks. It's also used
at linear playback for NEXT / PREVIOUS chapter.
SEARCH.DAT file
Due to VBR coding and the nature of the buffering used in MPEG-2 video coding
the relation between playing time and sector address is not fixed. This file
contains a list of Access Point sector addresses of the nearest Intra pictures
on a regular time interval for the MPEG tracks. This is usefull for features
such as time search.
TRARKS.SVD file
This file contains content related information as the Playing time, Video
system type, and number of audio streams for each MPEG track on the disc.
PSD.VCD file
This file contains the data for the Play Sequence Descriptor (PSD). The
size of the PSD may be variable, up to a maximum of 256 sectors or 512 KB.
LOT.VCD file
This 32 sectors file contains the List ID Offset Table (LOT). The LOT associates
List ID numbers with the corresponding List Offset values.
MPEG-2 directory
This directory contains the files that represent the MPEG-2 encoded Audio/Video
Tracks. Each MPEG-2 Track is represented by a file with the name "AVSEQnn.MPG",
where "nn" is the Sequence Number. The Sequence Numbers (nn) starts
with number = 01, and are incremented sequentially for each recorded MPEG track.
The file with the name "AVSEQ01.MPG" corresponds to Sequence Number
1 and is the only file in Track number 2.
SEGMENT directory
This directory is optional and contains the files that represent the Segment
Play Items. Each Segment Play Item is represented by a file with the name "ITEMnnnn.MPG",
where "nnnn" is the Segment Play Item Number.
EXT directory
This directory contains:
SCANDATA.DAT file
Used for playing time related access. This file contains a list of Access
Point sector addresses. For playing time access into a MPEG stream the sector
address can be found in the list by looking up the sector address for the corresponding
time. There is a sector address list for each MPEG track and for each motion
picture Segment Play item.
CAPTnn.DAT file.
For each track containing user data with Closed Caption information a file
shall be present Other (CD-ROM) files may be included in this directory, usually
intended for computer based systems.
3. MPEG-2
MPEG-2 Video
& Audio - Page 3
(Source
: Philips)
MPEG-2
The MPEG-2 Program Stream (PS) contains multiplexed Video, Audio, and Overlay
Graphics data, compressed in Elementary streams in PES packets. Variable Bit
Rate (VBR) coding is a method to significantly increase the efficiency of
MPEG-2 encoding, by adjusting the bit rate allocated based on the audio or
video complexity. More bits are used to encode scenes which are difficult
to compress; and less bits are used when the video or audio content is easier
to compress.
Synchronization among the Elementary streams is accomplished with Presentation
Time Stamps (PTS) in the Program Stream in reference to a common System Clock
Reference (SCR). These time-stamps describe the delivery time instances of
when a pack is taken from the track buffer and payload is extracted and placed
into the decoder which is associated with the packet ID.
SCR values are not a linear set of values as in Video CD 2.0,
but are dictated by the VBR packet scheduling. Presentation times for video
or audio frames without an associated PTS will be interpolated based on the
previous PTS and display duration of the video or audio frame. For the
case of still pictures, a PTS shall be coded for every still picture frame.
For the case of graphics overlay, a PTS shall be coded for every graphics
page.
MPEG-2 VIDEO format
There
are basically two types of Video encoded discs, namely either encoded from
PAL or NTSC source video data, however encoding may change from track to track.
The encoded video stream is stored in MPEG sectors. For the
coding of video, the constraints defined by MPEG for the Main Profile at Main
Level shall apply.
The pack and packet structure for Still Pictures are the same
as those specified for Motion Pictures. Each still picture shall be encoded
as an MPEG-2 Intra Frame.
MPEG AUDIO format
The
PS stream may contain two audio streams. The audio stream is selectable by
the user. In the audio stream the left audio channel is encoded as MPEG Audio
Channel zero (CH-0) and the right audio channel as MPEG Audio channel one
(CH-1).
For Karaoke use the dual channel mode only is used for special
music programs, with in one channel the music without the vocal part and in
the other channel the music with the vocal part; MPEG Audio channel one will
in this case contain the music with the vocal part.
For general use the dual channel mode can be used for two separate
languages without compromising video/audio quality. The MPEG Audio channel
CH-0 will in this case contain the default language.
It is only allowed to change the audio Mode within one Sequence
between stereo and joint stereo. MPEG audio can adapt the bit rate used by
the encoder every audio frame (26.1 ms) to the complexity of the sound to
be encoded. The use of VBR is optional on the disc, but the decoder in the
player must support this. Simple pieces of music demand a low bit rate, while
complex sound require a higher one. When VBR is used, the average bit rate
correspond to the average sound complexity, but at constant bit rate (CBR)
the bit rate is set for the most complex piece of sound. A typical gain is
30-40%.
Surround Sound can either be realized by coding a Dolby Surround
matrix encoded two-channel audio source with MPEG-1 Audio, or optionally by
coding a 5.1 channel audio source with MPEG-2 multi-channel (5+1) Backwards
Compatible audio. This mode is defined in the MPEG-2 Audio standard ( ISO/IEC
13818-3), and is fully compatible with MPEG-1. A MPEG-1 decoder will decode
the basic stereo ( left and right ) audio from the multi-channel MPEG-2 audio
signal. So it's an option to add a MPEG-2 multi-channel decoder.
4. The Program Stream
Private Data
Streams - Page 4
(Source
: Philips)
Besides video and audio, a Program Stream may contain other
elementary data streams. Because these are not defined in ISO/IEC 13818,
the syntax and semantics for these additional data streams are defined specially
for the Overlay Graphic data stream.
Overlay Graphics and Text (OGT)
The Overlay Graphics layer is designed for two main applications,
namely Movie subtitling and Karaoke lyrics. It is a full screen resolution
overlay with 4 colors, and transparency. Multi-color support is provided,
to allow for highlighting of song lyrics or other picture highlighting.
The main advantage of OGT is that the graphics and text are
not put into the video picture before encoding, but mixed in the decoder,
which allows for selectable language and improved picture quality. The encoder
model is based on two separate video planes; One for motion video, and one
for OGT. The OGT page is displayed on top of the Video picture.
Play Sequence Descriptor ( PSD )
This is a set of control structures that enables the playback
of preprogrammed sequences with user selection and interaction. The PSD
contains a set of basic control structures i.e. the Play List, Selection
List, and the End List. The Play List defines a list of Play Items that
are played in sequence. A Play Item may be one of the following items :
The whole or part of an MPEG Audio / Video Track. One, or more, MPEG encoded
Still Pictures; with or without MPEG Audio.
MPEG Audio with no pictures. Motion Picture; with or without
MPEG Audio The Selection List defines the action of the player in response
to various user inputs, and may be used to implement menu systems for user
selection of sequences. The Selection List may be extended to include hotspot
information or commandlists. The player must response to user actions (NEXT,
PREVIOUS, DEFAULT SELECTION, NUMERIC, RETURN). The Play List defines a list
of Play Items that are to be played sequentially.
The Selection List is used in the PSD.VCD file, and is a
List for implementing selection menus and enabling branching under user
control. Segment Play Items are encoded as MPEG Sectors and are restricted
to the Segment Play Item Area. Segment Play Items allow a Still Picture
mode. Play List extensions have been defined for more interactivity by a
Command List Interpreter and use of variables for storing scores and other
application variables.
USER data
User data is used to encode scan information and closed caption information.
The Scan Information Data is mandatory. On a Super Video CD disc it is only
allowed to encode user data in the picture layer of the MPEG Video stream.
Scan Information Data
It is mandatory to encode Scan Information in User data groups, and they
must be included as user data in the picture layer of all Intra pictures. Scan
Information data contains forward and backward pointers to Sectors that contain
the start of an Intra picture. Scan Information data is used for both Motion
Pictures and Still Pictures.
5. Software
SVCD Software
- Page 5
Ok..what software I will need ?
The most useful software for SVCD authoring is:
SVCD Hardware Encoders : (With them you are
going to encode Mpeg-2 from .Avi files..)
- MPEG MovieMaker
200
- MPEG Profiler
SVCD Software Encoders
- BB
Mpeg (its very very slow. Its takes about 6 hours to encode a 3 minute
SVCD music video on a Pentium 200MMX.)
SVCD supports (352x288, 352x576 and 480x576) for PAL. and
(352x240, 352x480, 480x480) for NTSC. But the SVCD option in bbMpeg supports
only 480x576 for PAL and 480x480 for NTSC (for now).
There are 2 main reasons most MPEG-2 software encoders are
not SVCD compliant:
1. SVCD requires a pack size of 2324 bytes (the same as
VCD). DVD requires a pack size of 2048 bytes. Most MPEG-2 software encoders
fixed the pack size at 2048 bytes. But they allow you to change the pack
size in MPEG-1 (2048 bytes default and 2324 bytes for VCD) but not in
MPEG-2.
2. The video stream must have User Data Scan Info to be SVCD compliant.
User Data Scan Info is not required for DVD.
Ligos has released profiles
for LSX Mpeg v3.0 supporting SVCD Video. We didn't test them yet to see
if they are accepted from any SVCD Authoring program.
Other Tools
Philips has released several SVCD Authoring Tools which
will make you create SVCD CDs (they only run into NT4..)
Philips
Super VideoCD Designer
"..To create a SuperVCD disc you first need to design
a disc using SVCD Designer. SVCD Designer enables you to create a Disc
Definition Script (DDS) which contains the information to generate the
required SuperVCD files.."
Philips
Super VideoCD Toolset
".. The SVCD Authoring Toolset will then use the DDS
and the required assets such as audio and video to create the SuperVCD
disc.."
Philips
Super VideoCD Verifier
"..The SVCD Verifier is a verification tool to support
the generation of data, compliant with both MPEG-2 and SVCD standards.
The verifier performs syntax checks as well as semantic and dynamic checks.
The tool generates a report with all detected violations of the standards.
Additionally, the input stream can be analysed and its contents on all
specified levels can be logged in a clear and concise way.."
EnReach
I-Author for SuperVCD
"..I-Author for SuperVCD is powerful authoring software.
It fully supports SVCD 1.0 specification and is backward compatible with
VCD 3.0, VCD 2.0, and VCD 1.1 formats. Especially designed for Windows
95, I-Author Deluxe for SuperVCD is
- Easy-to use wizards for disc creation
- Point-and-click graphical user interface (GUI)
- Supports nearly all MPEG-2 encoding systems and CD-R/CD-RW
drives.."
What about CDR Software?
Nero
by Ahead is the only software which can make an SuperVCD CD from a
SuperVCD Mpeg encoded file. However it doesn't support advance options
(like
menus
and subtitles..)
EnReach I-Author for SuperVCD saves file into .cif format (Adaptec's Ez CD
Creator).