CDXL is motion video

file format A file format is a standard way that information is encoded for storage in a computer file. It specifies how bits are used to encode information in a digital storage medium. File formats may be either proprietary or free. Some file formats ...

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, a ...

in the late 1980s and early 1990s for the

Amiga Amiga is a family of personal computers introduced by Commodore International, Commodore in 1985. The original model is one of a number of mid-1980s computers with 16- or 32-bit processors, 256 KB or more of RAM, mouse-based GUIs, and sign ...

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 fi ...

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

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transfers, thus achieving playback with a low

CPU A central processing unit (CPU), also called a central processor, main processor or just processor, is the electronic circuitry that executes instructions comprising a computer program. The CPU performs basic arithmetic, logic, controlling, an ...

load. As a result, CDXL can only support weak video compression and therefore relatively low video resolutions and moderate

frame rate Frame rate (expressed in or FPS) is the frequency (rate) at which consecutive images ( frames) are captured or displayed. The term applies equally to film and video cameras, computer graphics, and motion capture systems. Frame rate may also ...

s. 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 Ju ...

, the CDXL format has been extended to support

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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 The Motorola 68000 (sometimes shortened to Motorola 68k or m68k and usually pronounced "sixty-eight-thousand") is a 16/32-bit complex instruction set computer (CISC) microprocessor, introduced in 1979 by Motorola Semiconductor Products Sect ...

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, mak ...

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