CDXL is motion video

file format A file format is a Computer standard, 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 format, pr ...

developed by

Commodore Commodore may refer to: Ranks * Commodore (rank), a naval rank ** Commodore (Royal Navy), in the United Kingdom ** Commodore (India), in India ** Commodore (United States) ** Commodore (Canada) ** Commodore (Finland) ** Commodore (Germany) or ' ...

in the late 1980s and early 1990s for the

Amiga Amiga is a family of personal computers produced by Commodore International, Commodore from 1985 until the company's bankruptcy in 1994, with production by others afterward. The original model is one of a number of mid-1980s computers with 16-b ...

computer platform. It is notable for being one of the earliest formats created for motion video playback from

CD-ROM A CD-ROM (, compact disc read-only memory) is a type of read-only memory consisting of a pre-pressed optical compact disc that contains computer data storage, data computers can read, but not write or erase. Some CDs, called enhanced CDs, hold b ...

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 International Organization for Standardization, ISO and International Electrotechnical Commission, IEC that sets standards for media coding, includ ...

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 A central processing unit (CPU), also called a central processor, main processor, or just processor, is the primary processor in a given computer. Its electronic circuitry executes instructions of a computer program, such as arithmetic, log ...

load. As a result, CDXL can only support weak

video compression In information theory, data compression, source coding, or bit-rate reduction is the process of encoding information using fewer bits than the original representation. Any particular compression is either lossy or lossless. Lossless compression ...

and therefore relatively low video resolutions and moderate

frame rate Frame rate, most commonly expressed in frame/s, or FPS, is typically the frequency (rate) at which consecutive images (Film frame, frames) are captured or displayed. This definition applies to film and video cameras, computer animation, and moti ...

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 consists of computer programs that instruct the Execution (computing), execution of a computer. Software also includes design documents and specifications. The history of software is closely tied to the development of digital comput ...

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) is a home video game console developed by Commodore as part of the Amiga line, as well as the final hardware to be developed by the company. Released in September 1993 in Europe, Australia, Canada, and B ...

, 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 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 Sector ...

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 VHS (Video Home System) is a discontinued standard for consumer-level analog video recording on tape cassettes, introduced in 1976 by JVC. It was the dominant home video format throughout the tape media period of the 1980s and 1990s. Ma ...

. 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), (not to be confused with CD Video which is a type of Laserdisc) is a home video format and the first format for distributing films on standard optical discs. The f ...

encoded in

MPEG-1 MPEG-1 is a Technical standard, standard for lossy compression of video and Audio frequency, 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 ...

format allows approximately 72 minutes of 352×288 (PAL) 24-bit color video at 25 frame/s .

References

{{DEFAULTSORT:Cdxl Graphics file formats Amiga Computer file formats Digital container formats Film and video technology

Background

Usage

Performance

See also

References