Sustainability of Digital Formats: Planning for Library of Congress Collections
Sustainability of Digital Formats: Planning for Library of Congress Collections |
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| Introduction | Sustainability Factors | Content Categories | Format Descriptions | Contact | |
| Full name | QuickTime File Format |
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| Description |
File format that wraps video, audio, and other bitstreams. This description is concerned with QuickTime as a video wrapper (generally with a synchronized audio stream), called "movie" files by Apple, and as a sound wrapper, especially as used by Apple's iTunes music service. QuickTime also wraps still images (QuickTime Image Files), animations not recorded as video, virtual reality, etc., and these are not discussed at this site, with the exception of SWF_7 and SWF_8, the Flash SWF File Format (versions 7 and 8). Specialists describe QuickTime atoms as the format's fundamental building blocks. The MultimediaWiki reports, "Atoms are chunks of data in that comprise a QuickTime file. Sometimes they contain data and sometimes they contain other atoms. . . . An atom consists of a size, a type, and a data payload." As of February 2012, two versions of the file format specification were offered by Apple: the "classic" from 2001 and a newer version, as updated in 2012. Various sources, including the Wikipedia QuickTime article (consulted February 2, 2012), name a number of versions of QuickTime, from 1991 to the present, but these seem to be references to the QuickTime production or playback software rather than the file wrapper per se. |
| Production phase | Typically a final state format for end user delivery; sometimes a middle-state format, e.g., the source when producing lower-resolution streaming versions. |
| Relationship to other formats | |
| Has subtype | QTV_Apple, QuickTime Video, Apple Codec |
| Has subtype | QTV_Cinepak, QuickTime Video, Cinepak Codec |
| Has subtype | QTV_DV, QuickTime Video, DV Digital Video |
| Has subtype | QTV_MPEG, QuickTime Video, MPEG Codec |
| Has subtype | QTV_MJPEG, QuickTime Video, Motion JPEG Codec |
| Has subtype | QTV_MP4_V, QuickTime Video, MPEG-4 Visual Coding |
| Has subtype | QTV_MP4_AVC, QuickTime Video, MPEG-4 Advanced Video Coding |
| Has subtype | QTV_Sorenson, QuickTime Video, Sorenson Codec |
| Has subtype | QTV_SWF, QuickTime Video with SWF Flash |
| Has subtype | QT_210, QuickTime File Format with V210 Video Encoding. Uncompressed 10-bit 4:2:2 Picture. |
| Has subtype | QT_UYVY, QuickTime File Format with UYVY (2vuy) Video Encoding. Uncompressed 8-bit 4:2:2 Picture. |
| Has subtype | QT_YUY2, QuickTime File Format with YUY2 (yuv2) Video Encoding. Uncompressed 8-bit 4:2:2 Picture. |
| Has subtype | QTV_AppleProRes422, QuickTime Video, Apple ProRes 422 Codec Family |
| Has subtype | QTV_AppleProRes4444, QuickTime Video, Apple ProRes 4444 Codec Family |
| Has subtype | QuickTime movie variants defined by several other video codecs not documented at this time. |
| Has subtype | QTA_AAC, QuickTime Audio, AAC Codec |
| Has subtype | QTA_MP3, QuickTime Audio, MP3 Codec |
| Has subtype | QuickTime sound variants defined by other audio codecs, including uncompressed and lossless audio, not documented at this time. |
| Affinity to | QuickTime Image File Format, not documented at this time. |
| LC experience or existing holdings | The Library of Congress has a small amount of QuickTime files in its collections. |
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| LC preference | The Library of Congress Recommended Formats Statement (RFS) lists ProRes 4444 (XQ), 4444 or 422 HQ in a QuickTime wrapper as a Preferred format for Video - File-Based and Physical Media. |
| Disclosure | Fully documented. Proprietary format developed by Apple Computer, Inc. |
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| Documentation | QuickTime File Format Specification; both the "classic" (2001) and updated-through-2012 versions link from this menu page. |
| Adoption | Widely adopted. |
| Licensing and patents | Licensing by Apple appears to be limited to the software and other technology elements. |
| Transparency | The file format is relatively transparent. See information on the codecs contained in QuickTime files: Cinepak, Sorenson_3, MPEG-1, MJPEG, LPCM, AAC, and MP3. |
| Self-documentation | Technical metadata is in the headers for the atoms and container atoms that comprise a QuickTime file and also in the locations in the file. Descriptive ("bibliographic") metadata may be entered within the following annotations: "Album", "Artist", "Author", "Comment", "Copyright", "Creation Date", "Description", "Director", "Disclaimer", "Full Name", "Host Computer", "Information", "Make", "Model", "Original Format", "Original Source", "Performers", "Producer", "Product", "Software", "Special Playback Requirements", "Warning", and "Writer." |
| External dependencies | None |
| Technical protection considerations | QuickTime files may be structured to require end users to enter a media key before the file can be played. Newsgroup traffic about iTunes includes a statement from a commentator that reports, "iTunes uses a DRM system that prevents files to be played on more than 3 platforms and only the iTunes player can cope with that DRM system." |
| Still Image | |
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| Normal rendering | Good support. |
| Clarity (high image resolution) | Moderate to good, depending upon the type and level of compression, and the encoder used. See QTV_Apple, QTV_Cinepak, QTV_Sorenson, QTV_MPEG, and QTV_MJPEG. Extent of use of uncompressed video bitstream unknown. |
| Functionality beyond normal rendering | Supports various features, e.g., sprites, animation, virtual reality, etc. See Notes below for information about multiple timecodes. |
| Sound | |
| Normal rendering | Good support |
| Fidelity (high audio resolution) | Depends upon encoding; may be used with lossy encodings like MP3 (and many others) and uncompressed audio like LPCM, although this is limited to 16 bit word length. See also QTA_AAC and QTA_MP3. |
| Multiple channels | Not investigated for this description at this time. |
| Support for user-defined sounds, samples, and patches | Not investigated for this description at this time. |
| Functionality beyond normal rendering | Not investigated for this description at this time. |
| Tag | Value | Note |
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| Filename extension | mov qt |
For movie files. |
| Filename extension | m4p mp3 |
For sound files. The m4p extension is for QuickTime files containing AAC bitstreams purchased from iTunes and protected by a digital rights management scheme. Bookmarkable AAC files may carry the extension m4b. [The mp3 extension is for QuickTime sound files containing MP3 bitstreams; extent of protection unknown at this writing.] |
| Filename extension | qtif qti qif |
For QuickTime Image Files; from The File Extension Source. |
| Internet Media Type | video/quicktime video/x-quicktime image/mov |
For movie files. From From http://www.iana.org/assignments/media-types/video/quicktime and The File Extension Source. |
| Internet Media Type | Not found. | Comments welcome. For sound files; no MIME type found at this writing. |
| Internet Media Type | image/x-quicktime |
For image files; selected from The File Extension Source. |
| Magic numbers | Hex: xx xx xx xx 6D 6F 6F 76 ASCII: ....moov Hex: xx xx xx xx 66 72 65 65 ASCII: free |
From Gary Kessler's File Signatures Table. Kessler lists several other possible signatures for QuickTime. The first listed here is the most common; the second listed is declared in the DROID signature file for x-fmt/384, QuickTime. See Pronom PUID value below. |
| Mac OS file type | See note. | Video type tag (QuickTime). Four-character codes that vary according to the video codec selected; see the QuickTime File Format specification (2001), p. 92 or p. 96.1 |
| Uniform Type Identifier (Mac OS) | See note. | Audio type tag (QuickTime). Four-character codes that vary according to the audio codec selected; see the QuickTime File Format specification (2001), pp. 102-03 or pp. 107-9.1 |
| Pronom PUID | x-fmt/384 |
See http://www.nationalarchives.gov.uk/PRONOM/x-fmt/384. |
| Wikidata Title ID | Q942350 |
See https://www.wikidata.org/wiki/Q942350. |
| General | The documentation and retention of multiple timecodes may be of interest to those producing complete or authentic copies of a source item that may include multiple timecodes, e.g., LTC, VITC, or ANC. In historical recordings these are often not synchronized and may reveal aspects of how a given video program had been produced. QuickTime permits users to make as many timecode tracks as they wish, but experts report that this can inhibit interoperability and some tracks may not be properly read. Timecode data is stored in QuickTime's tmcd atom, one set of timecode data per tmcd atom. The timecode track in QuickTime has a label that many systems use to note an identifier of the source tape; for example, it stores the data of the "Reel" field in the Final Cut software application. |
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| History | Introduced in 1991; structured for use in Windows, 1994; in the mid-to-late 1990s, the format influenced the shape of MPEG-4. See the Wikipedia article on QuickTime (as consulted February 2012) for excellent detail. |
1There seem to have been at least two printings of the specification carrying the same date. These were not systematically compared by the compiler of this Web page. Pagination varies between these two printings.
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