CDXL
Encyclopedia
CDXL is an obsolete motion video file format
developed by Commodore
in the late 1980s and early 1990s for the Amiga
computer platform. It is notable for being one of the earliest formats created for motion video playback from CD-ROM
.
transfers and relied little on the CPU
. As a result CDXL could only support weak video compression and therefore relatively low video resolutions and moderate frame rate
s.
The CDXL format initially allowed playback of up to 24 frames per second with up to 4096 colors encoded in HAM-6. Audio support allowed for 8-bit mono or stereo sound. When the Amiga CD32
was released the format was able to support AGA color modes (up to 262,144 on-screen colors from a 24-bit color palette) and higher display resolutions.
Designed as a streaming format CDXL consists of linear concatenated chunks (packets), each with an uncompressed frame and associated audio data. There is no overall file header, just the header of each chunk. The frame rate is constant but not stored in the file, so it is necessary to set the playback speed in the player software manually.
CDXL is not related to ANIM
file format (a subset of Interchange File Format
) It is supported by AmigaOS
through CDXL.datatype which allows playback of CDXL files on compatible Amiga computers through standard universal, datatype-loader based, multimedia tool of AmigaOS called Multiview.
processor, OCS chipset and single-speed CD-ROM drive. A single-speed (150 kB
/s) CD-ROM drive permitted resolutions equivalent to 160×100 with 4,096 colors at 12 frame/s
with 11025 Hz 8-bit mono audio. At these settings audio and visual quality would be perceived as considerably worse than VHS
.
A CDXL stream at 300 kB/s (equivalent to 256×128 at 12 frame/s) allows approximately 36 minutes of video to fit on CD-ROM. In comparison, a Video CD
encoded in MPEG-1
format allows approximately 72 minutes of 384×280 24-bit color video at 25 frame/s http://ninjaw.ifrance.com/cd32/_docs/cdxl/cdxl.html.
File format
A file format is a particular way that information is encoded for storage in a computer file.Since a disk drive, or indeed any computer storage, can store only bits, the computer must have some way of converting information to 0s and 1s and vice-versa. There are different kinds of formats for...
developed by Commodore
Commodore International
Commodore is the commonly used name for Commodore Business Machines , the U.S.-based home computer manufacturer and electronics manufacturer headquartered in West Chester, Pennsylvania, which also housed Commodore's corporate parent company, Commodore International Limited...
in the late 1980s and early 1990s for the Amiga
Amiga
The Amiga is a family of personal computers that was sold by Commodore in the 1980s and 1990s. The first model was launched in 1985 as a high-end home computer and became popular for its graphical, audio and multi-tasking abilities...
computer platform. It is notable for being one of the earliest formats created for motion video playback from CD-ROM
CD-ROM
A CD-ROM is a pre-pressed compact disc that contains data accessible to, but not writable by, a computer for data storage and music playback. The 1985 “Yellow Book” standard developed by Sony and Philips adapted the format to hold any form of binary data....
.
Background
In an era shortly after the introduction of CD-ROM drives and before low cost MPEG decoding hardware became available the CDXL format was created primarily for the Amiga CDTV to permit playback of video from CD-ROM. CDXL was tailored for the Amiga chipset and took advantage of DMADirect memory access
Direct memory access is a feature of modern computers that allows certain hardware subsystems within the computer to access system memory independently of the central processing unit ....
transfers and relied little on the CPU
Central processing unit
The central processing unit is the portion of a computer system that carries out the instructions of a computer program, to perform the basic arithmetical, logical, and input/output operations of the system. The CPU plays a role somewhat analogous to the brain in the computer. The term has been in...
. As a result CDXL could only support weak video compression and therefore relatively low video resolutions and moderate frame rate
Frame rate
Frame rate is the frequency at which an imaging device produces unique consecutive images called frames. The term applies equally well to computer graphics, video cameras, film cameras, and motion capture systems...
s.
The CDXL format initially allowed playback of up to 24 frames per second with up to 4096 colors encoded in HAM-6. Audio support allowed for 8-bit mono or stereo sound. When the Amiga CD32
Amiga CD32
The Amiga CD32, styled "CD32" , was the first 32-bit CD-ROM based video game console released in western Europe, Australia, Canada and Brazil. It was first announced at the Science Museum in London, United Kingdom on 16 July 1993, and was released in September of the same year...
was released the format was able to support AGA color modes (up to 262,144 on-screen colors from a 24-bit color palette) and higher display resolutions.
Designed as a streaming format CDXL consists of linear concatenated chunks (packets), each with an uncompressed frame and associated audio data. There is no overall file header, just the header of each chunk. The frame rate is constant but not stored in the file, so it is necessary to set the playback speed in the player software manually.
CDXL is not related to ANIM
ANIM
ANIM is a file format, used to store digital movies and computer generated animations , and is a variation of the ILBM format, which is a subformat of Interchange File Format.-Anim FileTypes:...
file format (a subset of Interchange File Format
Interchange File Format
Interchange File Format , is a generic container file format originally introduced by the Electronic Arts company in 1985 in order to ease transfer of data between software produced by different companies....
) It is supported by AmigaOS
AmigaOS
AmigaOS is the default native operating system of the Amiga personal computer. It was developed first by Commodore International, and initially introduced in 1985 with the Amiga 1000...
through CDXL.datatype which allows playback of CDXL files on compatible Amiga computers through standard universal, datatype-loader based, multimedia tool of AmigaOS called Multiview.
Usage
A number of Amiga CD-ROM games and entertainment software from the era used CDXL for motion video.Performance
Playback was moderately impressive at the time of release given the CDTV's Motorola 68000Motorola 68000
The Motorola 68000 is a 16/32-bit CISC microprocessor core designed and marketed by Freescale Semiconductor...
processor, OCS chipset and single-speed CD-ROM drive. A single-speed (150 kB
Kilobyte
The kilobyte is a multiple of the unit byte for digital information. Although the prefix kilo- means 1000, the term kilobyte and symbol KB have historically been used to refer to either 1024 bytes or 1000 bytes, dependent upon context, in the fields of computer science and information...
/s) CD-ROM drive permitted resolutions equivalent to 160×100 with 4,096 colors at 12 frame/s
Frame rate
Frame rate is the frequency at which an imaging device produces unique consecutive images called frames. The term applies equally well to computer graphics, video cameras, film cameras, and motion capture systems...
with 11025 Hz 8-bit mono audio. At these settings audio and visual quality would be perceived as considerably worse than VHS
VHS
The Video Home System is a consumer-level analog recording videocassette standard developed by Victor Company of Japan ....
.
A CDXL stream at 300 kB/s (equivalent to 256×128 at 12 frame/s) allows approximately 36 minutes of video to fit on CD-ROM. In comparison, a Video CD
Video CD
Before the advent of DVD and Blu-ray, the Video CD became the first format for distributing films on standard 120 mm optical discs. The format is a standard digital format for storing video on a Compact Disc...
encoded in MPEG-1
MPEG-1
MPEG-1 is a standard for lossy compression of video and audio. It is designed to compress VHS-quality raw digital video and CD audio down to 1.5 Mbit/s without excessive quality loss, making video CDs, digital cable/satellite TV and digital audio broadcasting possible.Today, MPEG-1 has become...
format allows approximately 72 minutes of 384×280 24-bit color video at 25 frame/s http://ninjaw.ifrance.com/cd32/_docs/cdxl/cdxl.html.