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QuickTime is a multimedia framework developed by Apple Computer, capable of handling various formats of digital video, media clips, sound, text, animation, music, and several types of interactive panoramic images.
The most recent version is 7.1.3 and is available for Mac OS X and Microsoft Windows.
The QuickTime technology has three major components:
- a media player, known as QuickTime Player, which Apple makes available for free download on its website and bundles with each of its computers
- the QuickTime file format — openly documented and available for anyone to use royalty-free
- software development kits available for the Macintosh and Windows platforms. These kits allow people to develop their own software to manipulate QuickTime and other media files. These are free to registered developers (registration is free).
Free version — QuickTime Player
Apple releases official QuickTime media player software for Mac OS and Windows for free under the brand QuickTime Player. (Earlier versions had been named MoviePlayer.) A number of features are disabled in QuickTime Player. Users have to unlock these by upgrading to QuickTime Pro, for roughly $30. One disabled feature is the ability to view videos in "full screen" mode.
Paid upgrade — QuickTime Pro
QuickTime Pro is a paid upgrade for Apple Computer's free QuickTime media player technology.
QuickTime Pro enables among others the following features inside QuickTime player:
- Full-screen playback
- Note: Full-screen playback can be enabled in the free Mac OS X version with AppleScript 
- Note: Full screen playback can be achieved on Windows using Media Player Classic which uses installed QuickTime codecs
- Editing clips through the Cut, Copy and Paste functions, merging separate audio and video tracks, freely placing the video tracks on a virtual canvas with the options of cropping and rotation.
- Exporting (encoding) videos opened in QuickTime to a wide variety of different video codecs (MPEG-4, H.264, Animation, Sorenson, DV, M-JPEG, etc.), still graphic formats (TIFF, PICT, JPEG, etc.), and audio codecs (WAV, AIFF, AAC, Apple Lossless, etc.).
- Preset export settings for creating video files encoded in H.264 at 320×240 pixels to be viewed on the fifth generation and later iPods.
The full QuickTime Pro is included with Final Cut Studio.
In Mac OS X, the "Pro-only" features are actually available from within the QuickTime framework, and the limitations in the free version apply only to the QuickTime Player application. Other software that uses the QuickTime framework can use the save/export features without the need for a license, e.g. some video editing packages that rely on QuickTime for their export/import abilities do so by using the QuickTime framework, no matter if a Pro key is present or not, and iTunes and its audio encoders do not require the Pro license to work. Because of this, Apple has often been criticized for its decision to require Mac OS X users to buy a QuickTime Pro key to use certain Player features. 
A number of companies utilize QuickTime for their software, for example:
- Apple's media player iTunes utilizes QuickTime for its audio and video playback features
- the Encyclopædia Britannica on DVD requires QuickTime to play movie clips
- iScreensaver Designer makes screensaver installers for Mac OS 8.6 through OS X and Windows 98 through XP, and builds from either platform to the other, demonstrating QuickTime's cross-platform versatility and stability
- many software installation compact discs
Independent players for QuickTime 6 (MPEG-4) exist for many operating systems, and the FFmpeg library even supports the Sorenson video compression format, as well as the QDesign audio codec often used alongside it. Apple, however, has licensed Sorenson technology exclusively.
QuickTime Alternative, as the name implies, uses specific QuickTime libraries and an alternative media player to avoid a full QuickTime installation.
QuickTime file format
A QuickTime file (*.mov) functions as a multimedia container file that contains one or more tracks, each of which store a particular type of data, such as audio, video, effects, or text (for subtitles, for example). Each track in turn contains track media, either the digitally-encoded media stream (using a specific codec such as Cinepak, Sorenson codec, MP3, JPEG, DivX, or PNG) or a data reference to the media stored in another file or elsewhere on a network. It also has an "edit list" that indicates what parts of the media to use.
Internally, QuickTime files maintain this format as a tree-structure of "atoms", each of which uses a 4-byte OSType identifier to determine its structure. An atom can be a parent to other atoms or it can contain data, but it cannot do both.
Apple's plans for HyperCard 3.0 illustrate the versatility of QuickTime's file format. The designers of Hypercard 3.0 originally intended to store the equivalent of an entire HyperCard stack (similar in structure to a complete web site, with graphics, buttons and scripts) as a QuickTime interactive file.
The ability to contain abstract data references for the media data, and the separation of the media data from the media offsets and the track edit lists means that QuickTime is particularly suited for editing, as it is capable of importing and editing in place (without data copying) other formats such as AIFF, DV, MP3, MPEG-1, and AVI. Other later-developed media container formats such as Microsoft's Advanced Streaming Format or the open source Ogg and Matroska containers lack this abstraction, and require all media data to be rewritten after editing.
QuickTime and MPEG-4
On February 11, 1998 the ISO approved the QuickTime file format as the basis of the MPEG-4 Part 14 (.mp4) container standard. Supporters of the move noted that QuickTime provided a good "life-cycle" format, well suited to capture, editing, archiving, distribution, and playback (as opposed to the simple file-as-stream approach of MPEG-1 and MPEG-2, which does not mesh well with editing). Developers added MPEG-4 compatibility to QuickTime 6 in 2002. However, Apple delayed the release of this version for months in a dispute with the MPEG-4 licensing body, claiming that proposed license fees would constrain many users and content providers. Following a compromise, Apple released QuickTime 6 on 15 July 2002.
QuickTime 6 had limited support for MPEG-4 in that it could only encode and decode Simple Profile (SP). Advanced Simple Profile (ASP) features, like B-frames, were unsupported, making QuickTime-encoded MPEG-4 files compare terribly with XviD and other full-featured encoders. QuickTime 7 decodes both MPEG-4 SP and ASP, though the encoder is still SP-only.
QuickTime 7's H.264 encoder is claimed to be Main Profile, but actually Baseline Profile plus 1 B-frame support, the decoder supports Baseline, Extended, and most of Main Profile . High Profile features are unsupported.
Because both the MOV and MP4 containers can utilize the same MPEG-4 codecs, they are mostly interchangeable in a QuickTime-only environment. However, MP4, being an international standard, has more support. This is especially true on hardware devices, such as the Sony PSP and various DVD players; on the software side, most DirectShow / Video for Windows codec packs   include an MP4 parser, but not one for MOV.
In QuickTime Pro's MPEG-4 Export dialog, an option called "Passthrough" allows a clean export to MP4 without affecting the audio or video streams. One recent discrepancy ushered in by QuickTime 7 is that the MOV file format now supports multichannel audio (used, for example, in the high-definition trailers on Apple's site), while MP4 is limited to stereo. Therefore multichannel audio must be re-encoded during MP4 export.
Apple released the first version of QuickTime on December 2, 1991 as a multimedia add-on for System Software 6 and later. The lead developer of QuickTime, Bruce Leak, ran the first public demonstration at the May 1991 Worldwide Developers Conference, where he played Apple's famous 1984 TV commercial on a Mac, at the time an astounding technological breakthrough. Microsoft's competing technology — Video for Windows — did not appear until November 1992.
That first version of QuickTime laid down the basic architecture which survives essentially unchanged today, including multiple movie tracks, extensible media type support, an open-ended file format, and a full complement of editing functions. The original video codecs included:
- the Apple Video codec (also known as "Road Pizza"), suited to normal live-action video
- the Animation codec, which used simple run-length encoding and better suited cartoon-type images with large areas of flat color
- the Graphics codec, optimized for 8-bit images, including ones that had undergone dithering
Apple released QuickTime 1.5 for Mac OS in the latter part of 1992. This added the SuperMac-developed Cinepak vector-quantization video codec (initially known as Compact Video), which managed the unheard-of feat of playing back video at 320×240 resolution at 30 frames per second on a 25 MHz 68040 CPU. It also added text tracks, which allowed for things like captioning, lyrics, etc., at very little addition to the size of a movie.
In an effort to increase the adoption of QuickTime, Apple contracted an outside company, San Francisco Canyon Company, to port QuickTime to the Windows platform. Version 1.0 of QuickTime for Windows provided only a subset of the full QuickTime API, including only movie playback functions driven through the standard movie controller.
QuickTime 1.6.x came out the following year. Version 1.6.2 first incorporated the "QuickTime PowerPlug" which replaced some components with PowerPC-native code when running on PowerPC Macs.
Apple released QuickTime 2.0 for Mac OS in February 1994 — the only version never released for free. It added support for music tracks, which contained the equivalent of MIDI data and which could drive a sound-synthesis engine built into QuickTime itself (using sounds licensed from Roland), or any external MIDI-compatible hardware, thereby producing sounds using only small amounts of movie data.
Following Bruce Leak's departure to Web TV the leadership of the QuickTime team was taken over by Peter Hoddie.
QuickTime 2.0 for Windows appeared in November 1994.
The next versions, 2.1 and 2.5, reverted to the previous model of giving QuickTime away for free. They improved the music support and added sprite tracks which allowed the creation of complex animations with the addition of little more than the static sprite images to the size of the movie. QuickTime 2.5 also fully integrated QuickTime VR 2.0.1 into QuickTime as a QuickTime extension.
The release of QuickTime 3.0 for Mac OS on March 30, 1998 introduced the now-standard revenue model of releasing the software for free, but with additional features of the Apple-provided MoviePlayer application that end-users could only unlock by buying a QuickTime Pro license code.
QuickTime 3.0 added support for graphics importer components that could read images from GIF, JPEG, TIFF and other file formats, and video output components which served primarily to export movie data via FireWire. It also included the advanced Sorenson Video codec (licensed from Sorenson Media), and the QDesign Music codec for substantial audio compression. It also added video effects which programmers could apply in real-time to video tracks. Some of these effects would even respond to mouse clicks by the user, as part of the new movie interaction support (known as wired movies).
During the development cycle for QuickTime 3.0 part of the engineering team was working on a more advanced version of QuickTime to be known as QuickTime interactive or QTi. Although similar in concept to the wired movies feature released as part of QT 3.0, QTi was much more ambitious. It allowed any QuickTime movie to be a fully interactive and programmable container for media. A special track type was added that contained an interpreter for a custom programming language based on 68000 assembly language. This supported a comprehensive user interaction model for mouse and keyboard event handling based in part on the AML language from the Apple Media Tool.
The QTi movie was to have been the playback format for the next generation of HyperCard authoring tool. Unfortunately both the QTi and the HyperCard 3.0 projects were canceled in order to concentrate engineering resources on streaming support for QuickTime 4.0, and the projects were never released to the public.
Apple released QuickTime 4.0 for Mac OS on June 8, 1999. This added graphics exporter components which could write some of the same formats that the previously-introduced importers could read, though interestingly not GIF (possibly because of the LZW patent). It added the improved QDesign Music 2 codec and support for streaming, alongside the release of the free QuickTime Streaming Server.
QuickTime 4.1, released at the beginning of 2000, added support for movie files larger than 2 gigabytes on Mac OS 9 and later, and dropped support for 68K Macs. Users gained the ability to control the QuickTime Player via AppleScript.
QuickTime 5.0 for Mac OS appeared on April 23, 2001. It added "skins" to the QuickTime Player and multiprocessor image compression support. The QuickTime VR component gained the ability to display cubic VR movies. Due to technical complications, the more advanced Sorenson Video 3 codec was not introduced until the QuickTime 5.0.2 release on July 1, 2001. Also, QuickTime 5.0.5 was the last version that supported Windows 95.
QuickTime 6.0 for Mac OS, released on July 15, 2002, was a major update, introducing MPEG-4 capabilities, including MPEG-4 Part 2 video and AAC. MPEG-2 playback was available with the purchase (due to MPEG licensing fees) of an additional component.
QuickTime 7 was released on April 29, 2005 with Mac OS X v10.4 featuring complete MPEG-4 compliance, H.264/MPEG-4 AVC codec, live resizing, multi-channel audio, full-screen overlay, and support for interactive animations created with Apple's new tool Quartz Composer. Version 7 was also released for 10.3.9.
On June 6, Apple issued a preview release of QuickTime 7.0 for Windows 2000 and Windows XP. This was followed by "Public Preview 2" on July 13, "Public Preview 3" on August 14, and the first final release on September 7, 2005.
Creating software that uses QuickTime
Developers can use the QuickTime software development kit to develop multimedia applications for Mac or Windows with the C programming language or with the Java programming language (see QuickTime for Java).
QuickTime consists of two major subsystems: the Movie Toolbox and the Image Compression Manager. The Movie Toolbox consists of a general API for handling time-based data, while the Image Compression Manager provides services for dealing with compressed raster data as produced by video and photo codecs.
QuickTime 7.0 introduced the QuickTime Kit (aka QTKit), a developer framework that is intended to replace previous APIs for Cocoa developers. This framework is for Mac only, and exists as Objective-C abstractions around a subset of the C interface. The upcoming Mac OS X Leopard will extend QTKit to full 64-bit support.
- List of media players
- Comparison of media players
- QuickTime VR
- Apple - QuickTime - Apple's official site
- Download page
- Older versions of QuickTime
- QuickTime content
- Apple's QuickTime developer site