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CD & DVD Premastering
Premastering processes depend on the format, eg CD
audio, CD-ROM, DVD-Video, DVD-Audio etc |
Before replication can begin the data content of the disc (whether CD
or DVD) must be premastered. This involves taking the source data
(as computer files for CD-ROM and DVD discs) and creating a disc image
on a suitable tape or disc format.
CD Audio
Premastering
CD Audio is the only format where the data (ie audio in this case) is
not stored on the disc as data files. The audio data will normally
be provided with the correct sampling frequency (ie 44.1 kHz) and
quantisation (16 bits per channel). Audio premastering therefore
usually starts with digital audio (eg on U-matic, DAT or CD-R) and
includes the following operations:
- PQ encoding (adding Table of Contents data with track start times)
- Editing and Compilation, which is made easy
with modern PC based editors. Audio can be input from various
sources including CD, DAT or U-matic, stored
on hard disk, edited and written to Exabyte or CD-R. Editing includes compilations, sample
rate conversion, cross fades, equalisation, dynamic range compression etc.
- Sample rate conversion, eg from 48kHz (eg on
some DATs) to the 44.1kHz needed for CD.
CD-ROM Premastering
CD-ROM titles can include games, multimedia titles and computer
databases and these will need to be created using specific software tools
and will include software development and authoring processes. The
end result will usually be a CD-R containing the complete application (or
multiple CD-Rs if the application will not fit on one disc), which is used
for glass mastering, without any further premastering operations. In
some cases a separate premastering process may be needed and this depends on the final
format. Examples of premastering processes are:
- Formatting to ISO 9660, HFS or hybrid formats to play on both
Windows and Mac platforms from individual files on
tape, CD or hard disk. With the widespread use of CD-Recorders
this is becoming increasingly rare as a separate premastering process.
-
Video CD formatting which is
normally part of the authoring process.
- CD EXTRA
formatting using the Blue Book multisession format with mode 2 sectors
and, optionally, with hybrid format for PC/Macintosh. This will
often involve combining the audio and data sessions ready for glass
mastering.
- CD
Graphics and CD TEXT
formatting including R to W subcode data.
DVD-Video
Premastering
DVD-Video Premastering is usually a complex process, which involves video and audio compression, graphics editing,
authoring and testing. The finished application data must be formatted
according to the appropriate DVD specification and transferred to DLT
(digital linear tape) for glass mastering.
DVD-5 discs can alternatively be mastered from a DVD-R disc unless the
application needs copy protection. DVD-10 discs can also be mastered from
two DVD-Rs discs in the same way. DVD-9 discs can be mastered only from
DLT.
Where copy protection is required, for DVD-Video or DVD-Audio, certain
steps need to be taken during premastering. For CSS (DVD-Video) the CSS
flags must be set and the VTS's to be protected must be marked. This is
normally easy to carry out using the premastering tools available.
DVD-Audio
Premastering
DVD-Audio premastering is similar to DVD-Video, using similar
authoring and premastering tools. The audio must be prepared as
PCM data at the appropriate sampling frequency (eg 96kHz) and
quantisation (eg 24 bits) in up to 5 channels (for surround
sound). This audio is then converted to MLP, together with a
stereo downmix if required. Authoring will add optional still
images, menus, subpictures and video.
DVD-Audio titles can use CPPM copy protection and the premastering tool must add two dummy files
(DVDAUDIO.MKB
and DVDAUDIO.BUP) which will, after glass mastering, contain the Media Key
Block (MKB) data for that disc.
The result of premastering will normally be an image file plus DDP file
and control data stored on a DLT tape. But DVD-R (both authoring and
general use) may be used for a DVD-5 if there is no copy protection or
region coding required.
DVD-ROM Premastering
DVD-ROM premastering is similar to CD-ROM premastering with the
following differences:
- DVD-ROM discs are much larger so the data needs to be written to
DVD-R or DLT for mastering.
- DVD-ROMs that require a DVD-9 (dual layer disc) must be
premastered and the data written to two DLTs, one for each
layer. Two DVD-Rs are not suitable because the two layers must
be a single volume with one file system instead of two. The
final disc will be formatted as a parallel track path disc (unlike
DVD-Videos which are usually opposite track path) with the file
system data on layer 0.
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