SVCD, or Super Video Compact Disc, is a standard for MPEG2 video on an ordinary Compact Disc. It is similar to DVD in that it supports playlists, multiple audio tracks, subtitle overlays, and menuing. Unlike DVD Video, however, it is stored on inexpensive compact discs. A typical movie in SVCD format will span two or three 700mb CD-ROMs.
S@@@@@@@@@@@1 Z#######S S#######X J#KS@J EKSK# #ggg@@KZ; #ggg# g#######g ,#ggggggg#
K############### .###########Z 2########### W##### Z##### ########### Z###### Z###########KW#########
W## E## :### #### X### ### X##M### ##2### ### ### ### ### #### #### :### ,
H## M## 7### g### ###J X### ##1 ### ### ### ### H### J### #### ;###
H## ### 7### g### ###J X### ### ## ### ########### ### ### #### 3###
H## ### ,### #### Z### ### X### ##@### ### ##########7 ########### @### #### 3###
H## ### ###########i 1########### #### Z#### ### ### ### ###i ###########H H###
H## ### JKBBBg2, ,2gBBHKJ :KJg Xi37 HiE Mi@ K@33 2SW ,JKBBB@2: .KiM
3## ###
;g#############H### ### 7EWMMMMMMMMWWZ ZE########################g i@#####################K:
2####################7 ### ################ ############################### K#############################i
#### ### ### ### 7###J @## #### ####
### ### ### ### ### ### ### ###
### W###Z ### ### ### ### ### ### @###@ ###
### X######### H## ### ### M## @## ### ######### ###
### 3### ### E## ### ### M## ##################### ### ### ### ###
### ### K## E## ### ### M## ,####################Z ### ### ### ###
### ### H## E## ### ### M## ### ### ### ### ###
### ### H## E## ### ### M## g### . ### ### ### ###
### ### H## E## ### ### M## ###################B ### ### ###############
### ### H## E## ### ### M## M###J ### ### #############
### ### H## E## ### ### ### ### ### ###
### ### H## E## ### ### ### ### ### ###
### ### H## E## ### ### #### ### ### ###
### ### H## E## ### ### .##################B ### ### ### S#############B
### ### H## E## ### ### S################## ### ### ### ###;:iiiii7 ###
### ### H## E## ### ### ### ### ### ### ### ###
### ### B## E## ### ### ### ### ### ### ### ###
### ### B## E## ### ### ####################### ### ### ### ### ###
### ### S### B## ### ### ###B ....... ### ### ###J S### ###
### ########g K## ### ### ### ### ### ########H ###
### :7 K## ### ### ### ### ### .7: ###
;### i## ### ### ### ### g### ###
####E7 ### ###1 ### ###M :::::::::::::71iiiiiiiiX##### 7####B; 7M####
################################# .##############H ##############################B ###########################
,##################################################################################################################################
#######MBKSSKBM###WWM######MWW##E@ggggg@E###E@ggggggHM#W@ggggggHM########MEW########EEMWW##MHgggggg@W####W@ggggggBM###W@KSSKBM########
### ###
### ########## B# #K ##W####### #########. W########## ## M#Z M# ##########S #########3 ########## ###
### # ## i# #: ## #g ## J# # #M ## J# # 2# S# S# # ###
### ## i# #: ## #S ## J# 2# 1# ## J# #1 # S# S# # ###
### X######## i# #: ########## ######### J######### ## 2# J# #1 # S######## X# # ###
### ; # i# #: ## ## J# ## ## #E J# #1 # S# S# # ###
### #@ # 2# #; ## ## J# E# 1# M# J# # ## S# X# # ###
### ########## ########## ## #########; ## ## ###, ## ########## #########X ########## ###
### ###
######################################################################################################################################
M################################################################################################################################W
Figure 1. SVCD Logo
TECHNICAL
SPECIFICATIONS
SVCD specifies a maximum total bitrate (for audio and video) of 2.6Mbps, or 2756kbps. Both video and audio may be of fixed or variable rate (VBRE). Video is encoded in the MPEG2 format and may be encoded at any of four different resolutions; 480x480 for NTSC, and 480x576 or for PAL. Audio is stereo MPEG1 Layer 2 (mp2) and may be from 32 to 384kbps, or encoded in an MPEG-1 5.1 format which is backwards compatible, as per ISO/IEC 13818-3. MPEG-1 decoders will extract basic stereo audio from this stream, but an MPEG-2 decoder will play it as full 5+1 channel. Also allowed are still images in MPEG2 format.
The SVCD format also supports overlay graphics and text, primarily for the purpose of displaying subtitles.
PLAYING
SVCDS
As SVCD is essentially somewhere between VCD and DVD, the hardware necessary to play them exists in every DVD player. Unfortunately, not all DVD players (software or hardware) include support for SVCD. In addition, some DVD players (such as those from Apex Digital Inc.) support only a subset of SVCD features, sometimes dropping graphics overlay support for example.
As SVCD is a standard which is rapidly gaining acceptance in the marketplace, especially in China which does not like being tied to standards outside of its control, support for SVCD is making it into more and more consumer appliance-level DVD players, including those from JVC, Pioneer, and others. It is also found in many Chinese (and similar) players, such as those from Apex, Raite, and Sampo.
Most current software DVD decoders will also play SVCDs, including PowerDVD and WinDVD. There is also a plugin for Windows Media Player which plays VCD and SVCD, but is somewhat unreliable.
MAKING
SVCDS
Making an SVCD "by hand" is a theoretically possible but extremely difficult task because the specification must be followed precisely. A number of different commercial software packages (as well as a certain amount of freeware) will make SVCDs of varying complexity for you.
Ahead's Nero - Burning Rom software will make SVCDs, though if you want it to do the MPEG2 compression you need to purchase an additional module. CeQuadrat is adding SVCD support to VideoPack 5.0. Enreach has a package called EnReach I-Author for SuperVCD. This is all Windows software; For MacOS there is a package from Compact Data Inc. called Super VCDMaker. Philips has their own package for SVCD authoring; SVCD Designer, SVCD Toolset, and SVCD Verification.
There are a number of freeware products which will make SVCDs. Perhaps the most popular is DVD2SVCD, which will rip a DVD and make an SVCD with a minimum of work. It uses TMPGENC or Cinema Craft Encoder to do the actual encoding, and it will make CD images for you, with subtitles, chapter marks, multiple audio streams, and other niceties.
DISC
FORMAT
SVCDs are recorded in CD-ROM XA format, with one Mode 2 Form 1 (2048 bytes/sector) data track and one or more Mode 2 Form 2 (2324 bytes/sector) tracks containing MPEG data. Mode 2 Form 2 tracks have no ECC, thus relying on MPEG to do error correction. Before and after these tracks are the lead-in and lead-out areas, respectively. This format does not allow any MPEG1 or CDDA (Red Book audio) tracks.
DATA
TRACK
The ISO 9660 data track of an SVCD contains (at minimum) three directories: SVCD, EXT, and MPEG-2. SVCD Information files (INFO.VCD, ENTRIES.VCD, LOT.VCD, PSD.VCD, SEARCH.DAT, and TRACKS.VCD.
Root Directory
|-- SVCD
| |-- INFO.VCD
| |-- ENTRIES.VCD
| |-- SEARCH.DAT
| |-- TRACKS.SVD
| |-- PSD.VCD
| |-- LOT.VCD
|-- MPEG-2
| |-- AVSEQ01.MPG
| |-- ACSEQ02.MPG
| |-- AVSEQnn.MPG
|-- SEGMENT
| |-- ITEM0001.MPG
| |-- ITEM0002.MPG
| |-- ITEMnnnn.MPG
|-- EXT
|-- SCANDATA.DAT
|-- CAPTnn.DAT
Figure 2. Sample Directory Structure1
Files in the SVCD directory
- INFO.VCD
Here is the first part of a INFO.VCD (actually INFO.SVD) file made by DVD2SVCD:
SUPERVCD^A^@FRIDAY ^@^B^@^A^A^@
Where ^@ is a null (ASCII 0.)
This file indicates that the disc is a Super VCD, and gives the name of the title. It can also contain other information such as what other discs are related.
- ENTRIES.VCD
This file contains the start and stop sector offsets for the MPEG tracks on the SVCD. It is used to control playback and track skipping.
- SEARCH.DAT
This file contains information to aid in synchronization of audio and video and for doing time searches. It is necessary because of the use of VBRE MPEG streams.
- TRACKS.SVD
This gives information for all video tracks on the disc.
- PSD.VCD
This file contains the data for the Play Sequence Descriptor (PSD). It can be up to 512kB in size.
- LOT.VCD
This file contains the List ID Offset Table, used to jump to named offsets on the disc.
The MPEG-2 Directory
This directory contains files representing the Mode 2 Form 2 MPEG tracks on the disc. Each file is named AVSEQnn.MPG, where nn is a two-digit number starting at 01 and increasing with the track number (The value is the track number - 1 such that the first file is AVSEQ01.MPG.)
The SEGMENT Directory
This directory (if present) contains files which represent MPEG-format still images. They are numbered beginning at 0001 (ITEM0001.MPG) and incremented serially.
The EXT Directory
This contains the SCANDATA.DAT file which contains access point sector addresses used for finding sector offsets based on time.
It can also contain CAPTnn.DAT files which describes closed-captioning information (subtitles.)
Finally, this directory can also contain optional files such as a SVCD playing application.
OVERLAY
GRAPHICS
The SVCD format allows for up to four 4-color plus transparency graphics overlay layers intended for subtitles and/or karaoke text.
XSVCD
XSVCD refers to technically non-compliant SVCDs which will nonetheless function in the majority of players. They tend to contain video clips at higher or lower resolutions than normally supported in order to either gain quality, or save space.
XSVCDs work (in some cases) because DVD players need to support these other resolutions and bitrates for other types of content, like VCD or DVD.
References:
- Super Video Compact Disc, a Technical Explanation. Philips, 2002.(http://www.licensing.philips.com/includes/download.php?id=2698&filename=2450.pdf)
- Ian Willis, Introduction to SVCD (Super VideoCD). Digital Video Information, 2002. (http://digvid.info/media/svcd.php)