View source for CDXL

{{short description|Commodore video file format}}
'''CDXL''' is motion video [[file format]] developed by [[Commodore International|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]].<ref>{{cite web |last=Sassenrath |first=Carl |title=Carl Sassenrath - Background Info |url=http://www.sassenrath.com/carl.html |website=CARL SASSENRATH - Architect of Operating Systems and Languages}}</ref><ref>{{Cite web |title=A500.org - downloads/video/cdxlplay.lha |url=http://www.a500.org/downloads/video/cdxlplay_lha.readme |access-date=2023-05-09 |website=www.a500.org}}</ref>

==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 [[Commodore CDTV]], to permit playback of video from CD-ROM. CDXL is tailored for the [[Amiga Original chipset|Amiga chipset]] and takes advantage of [[Direct memory access|DMA]] transfers, thus achieving playback with a low [[Central processing unit|CPU]] load.<ref>{{Cite patent|number=5293606|title=Apparatus and method for transferring interleaved data objects in mass storage devices into separate destinations in memory|gdate=1994-03-08|invent1=Sassenrath|inventor1-first=Carl E.|url=https://www.freepatentsonline.com/5293606.html}}</ref> As a result, CDXL can only support weak [[video compression]] and therefore relatively low video resolutions and moderate [[frame rate]]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]] manually. The CDXL format initially allowed playback of up to 24 frames per second with up to 4096 colors encoded in [[Hold And Modify#HAM6 operation|HAM-6]]. Audio support allows for 8-bit mono or stereo sound. With the advent of the [[Amiga CD32]], the CDXL format has been extended to support [[Amiga Advanced Graphics Architecture|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]] through its [[Amiga support and maintenance software#Datatypes|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, [[Amiga Original chipset|OCS]] chipset and single-speed CD-ROM drive constraints. A single-speed (150 [[KiloByte|kB]]/s) CD-ROM drive permits resolutions equivalent to 160×100 with 4,096 colors at 12 [[Frame rate|frame/s]] with 11025&nbsp;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]] encoded in [[MPEG-1]] format allows approximately 72 minutes of 352×288 (PAL) 24-bit color video at 25 frame/s .<ref>{{Cite web |date=2008-10-29 |title=CDXL = BILD und TON |url=http://ninjaw.ifrance.com/cd32/_docs/cdxl/cdxl.html |access-date=2023-05-09 | archive-url=https://web.archive.org/web/20081029234112/http://ninjaw.ifrance.com/cd32/_docs/cdxl/cdxl.html | archive-date=2008-10-29 }}</ref>

==See also==
{{Portal|Amiga}}
* [[ANIM]]
* [[Interchange File Format]]

== References ==
<references/>

{{AmigaOS}}

{{Compression formats}}
{{Media player (application software)}}

{{DEFAULTSORT:Cdxl}}
[[Category:Graphics file formats]]
[[Category:Amiga]]
[[Category:Computer file formats]]
[[Category:Digital container formats]]
[[Category:Film and video technology]]