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Appeared on: Tuesday, February 19, 2002
SuperVCD Format


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.

    

Super VideoCD SpecificationsSVCD 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

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).



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