CDXL is motion video
file format developed by
Commodore
Commodore may refer to:
Ranks
* Commodore (rank), a naval rank
** Commodore (Royal Navy), in the United Kingdom
** Commodore (United States)
** Commodore (Canada)
** Commodore (Finland)
** Commodore (Germany) or ''Kommodore''
* Air 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.
Background
In an era shortly after the introduction of CD-ROM drives and before low cost
MPEG
The Moving Picture Experts Group (MPEG) is an alliance of working groups established jointly by ISO and IEC that sets standards for media coding, including compression coding of audio, video, graphics, and genomic data; and transmission and f ...
decoding hardware became available the CDXL format was created, primarily for the
Commodore CDTV
The CDTV (from Commodore Dynamic Total Vision, later treated as a backronym for Compact Disc Television) is a home multimedia entertainment and video game console – convertible into a full-fledged personal computer by the addition of optional ...
, to permit playback of video from CD-ROM. CDXL is tailored for the
Amiga chipset and takes advantage of
DMA transfers, thus achieving playback with a low
CPU load.
As a result, CDXL can only support weak
video compression and therefore relatively low video resolutions and moderate
frame rates.
CDXL is a simple streaming format, consisting of linear concatenated chunks (packets), each with an uncompressed frame and associated audio data. There is no overall file header, just a header per 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
Software is a set of computer programs and associated software documentation, documentation and data (computing), data. This is in contrast to Computer hardware, hardware, from which the system is built and which actually performs the work.
...
manually. The CDXL format initially allowed playback of up to 24 frames per second with up to 4096 colors encoded in
HAM-6. Audio support allows for 8-bit mono or stereo sound. With the advent of the
Amiga CD32
The Amiga CD32 (stylized as Amiga CD32, code-named "Spellbound") is a 32-bit home video game console developed by Commodore and released in Europe, Australia, Canada, and Brazil. It was first announced at the Science Museum in London on July 16, ...
, the CDXL format has been extended to support
AGA color modes (up to 262,144 on-screen colors from a 24-bit color palette) and higher display resolutions.
Usage
A number of Amiga CD-ROM games and entertainment software uses CDXL for motion video.
CDXL is supported by
AmigaOS
AmigaOS is a family of proprietary native operating systems of the Amiga and AmigaOne personal computers. It was developed first by Commodore International and introduced with the launch of the first Amiga, the Amiga 1000, in 1985. Early versions ...
through its
datatype system, which allows playback of CDXL files on compatible systems.
Performance
Playback performance can be thought of as impressive at the time of release given the CDTV's
Motorola 68000 processor,
OCS chipset and single-speed CD-ROM drive constraints. A single-speed (150
kB/s) CD-ROM drive permits 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 is 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
Video CD (abbreviated as VCD, and also known as Compact Disc Digital Video) is a home video format and the first format for distributing films on standard optical discs. The format was widely adopted in Southeast Asia, Central Asia and the ...
encoded in
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 about 1.5 Mbit/s (26:1 and 6:1 compression ratios respectively) without excessive quality loss, making ...
format allows approximately 72 minutes of 352×288 (PAL) 24-bit color video at 25 frame/
External links
CDXL player software
References
{{DEFAULTSORT:Cdxl
Graphics file formats
Amiga
Computer file formats
Digital container formats
Film and video technology