Pregap
Encyclopedia
The pregap on a Red Book
audio CD is the portion of the audio track that precedes "index 01" for a given track in the table of contents (TOC). The pregap ("index 00") is typically two seconds long and usually, but not always, contains silence. Popular uses for having the pregap contain audio are live CDs, track interludes, and hidden song
s in the pregap of the first track (detailed below).
This method was quickly made obsolete in late 1996 when an update to Windows 95
in driver SCSI1HLP.VXD made the pregap track inaccessible. It is unclear whether or not this change in Microsoft Windows' behavior was intentional: for instance, it may have been intended to steer developers away from the pregap method and encourage what became the Blue Book specification
"CD Extra" format.
, the pregap contains a hidden track
. The track is truly hidden in the sense that most conventional standalone players and software CD players will not see it.
Such hidden tracks can be played by playing the first song and "rewinding" (more accurately, seeking in reverse) until the actual start of the whole CD audio track.
Not all CD drives can properly extract such hidden tracks. Some drives will report errors when reading these tracks, and some will seem to extract them properly, but the extracted file will only contain silence.
Currently does not support more than a 2 second pre-gap in the first track under its CD burning utilities
. Using a combination of Roxio's Toast
and a custom .cue file can provide a way around this.
Ripping of pregap audio is supported by the application X Lossless Decoder.
Windows XP:
Linux:
Red Book (audio CD standard)
Red Book is the standard for audio CDs . It is named after one of the Rainbow Books, a series of books that contain the technical specifications for all CD and CD-ROM formats.The first edition of the Red Book was released in 1980 by Philips and Sony; it was adopted by the Digital Audio Disc...
audio CD is the portion of the audio track that precedes "index 01" for a given track in the table of contents (TOC). The pregap ("index 00") is typically two seconds long and usually, but not always, contains silence. Popular uses for having the pregap contain audio are live CDs, track interludes, and hidden song
Hidden track
In the field of recorded music, a hidden track is a piece of music that has been placed on a CD, audio cassette, vinyl record or other recorded medium in such a way as to avoid detection by the casual listener...
s in the pregap of the first track (detailed below).
Computer data in pregap
The pregap was used to hide computer data, tricking computers into detecting a data track whereas conventional CD players would continue to see the CD as an audio CD.This method was quickly made obsolete in late 1996 when an update to Windows 95
Windows 95
Windows 95 is a consumer-oriented graphical user interface-based operating system. It was released on August 24, 1995 by Microsoft, and was a significant progression from the company's previous Windows products...
in driver SCSI1HLP.VXD made the pregap track inaccessible. It is unclear whether or not this change in Microsoft Windows' behavior was intentional: for instance, it may have been intended to steer developers away from the pregap method and encourage what became the Blue Book specification
Blue Book specification
The Blue Book or Enhanced Music CD specification describes the Enhanced Music CD format. The first session of an Enhanced Music CD contains audio information according to the Red Book...
"CD Extra" format.
Hidden audio tracks
On certain CDs such as the Think Tank by BlurBlur (band)
Blur is an English alternative rock band. Formed in London in 1989 as Seymour, the group consists of singer Damon Albarn, guitarist Graham Coxon, bassist Alex James and drummer Dave Rowntree. Blur's debut album Leisure incorporated the sounds of Madchester and shoegazing...
, the pregap contains a hidden track
Hidden track
In the field of recorded music, a hidden track is a piece of music that has been placed on a CD, audio cassette, vinyl record or other recorded medium in such a way as to avoid detection by the casual listener...
. The track is truly hidden in the sense that most conventional standalone players and software CD players will not see it.
Such hidden tracks can be played by playing the first song and "rewinding" (more accurately, seeking in reverse) until the actual start of the whole CD audio track.
Not all CD drives can properly extract such hidden tracks. Some drives will report errors when reading these tracks, and some will seem to extract them properly, but the extracted file will only contain silence.
OS support
Mac OS X:Currently does not support more than a 2 second pre-gap in the first track under its CD burning utilities
Disk Utility
Disk Utility is the name of a utility created by Apple for performing disk-related tasks in Mac OS X. These tasks include:*the creation, conversion, compression and encryption of disk images from a wide range of formats read by Disk Utility to .dmg or—for CD/DVD images—.cdr, which is identical to...
. Using a combination of Roxio's Toast
Roxio Toast
Roxio Toast is an Optical disc authoring and media conversion software application for Mac OS X. Its name is a play on the word burn, a term used for the writing of information onto a disc through the use of a laser....
and a custom .cue file can provide a way around this.
Ripping of pregap audio is supported by the application X Lossless Decoder.
Windows XP:
- Exact Audio CopyExact Audio CopyExact Audio Copy is a proprietary CD ripping program for Microsoft Windows. It has also been tested to work under newer versions of Wine on Linux...
provides the functionality to write to Index 0
Linux:
- cdrecord supports writing any kind of pregap
- cdrdaoCdrdaocdrdao is open source software for authoring and ripping of CD-ROMs. The software is released under the GPL. Cdrdao records audio or data CD-Rs in Disk-At-Once mode based on a textual description of the CD contents...
supports writing any kind of pregap - K3BK3bK3b is a CD and DVD authoring application by KDE for Unix-like computer operating systems. It provides a graphical user interface to perform most CD/DVD burning tasks like creating an Audio CD from a set of audio files or copying a CD/DVD, as well as more advanced tasks such as burning eMoviX...
, a frontend for several CD/DVD burning/ripping utilities, supports hiding the first track in the pregap of the second one.
External links
- History of Mixed-Mode CDs
- Technical Specifications of the Squirrel Nut ZippersSquirrel Nut ZippersThe Squirrel Nut Zippers are a band formed in 1993 in Chapel Hill, North Carolina by James "Jimbo" Mathus , Katharine Whalen , Chris Phillips on drums, Don Raleigh on bass and sideman Ken Mosher....
"Hot" ECD