Sustainability of Digital Formats
Planning for Library of Congress Collections
Sustainability of Digital Formats
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| Introduction | Sustainability Factors | Content Categories | Format Descriptions | Contact | |
| Full name | QuickTime File Format |
|---|---|
| Description | File format that wraps video, audio, and other bitstreams. This web site is concerned with QuickTime video presentations (generally with a synchronized audio stream), called "movie" files by Apple, and sound recordings, especially those distributed via 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). |
| Production phase | Typically a final state format for enduser 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 | QuickTime movie variants defined by several other video codecs, including uncompressed and lossless video, not documented at this time. |
| Has subtype | QTA_AAC, (audio file with specific codec) |
| Has subtype | QTA_MP3, (audio file with specific codec) |
| Has subtype | QuickTime sound variants defined by other audio codecs, including uncompressed and lossless audio, not documented at this time. |
| Has subtype | QuickTime Image File Format, not documented at this time. |
| LC experience or existing holdings | Limited to video: American Memory has produced QuickTime files for web service since the mid-1990s, typically using the Cinepak codec at 10 fps and 160x120 pixels. For the special videos associated with the Dance Instruction Manuals collection, a second set of higher-resolution QuickTime files was produced, using the Sorenson codec at 15 fps and 320x240 pixels. The audio stream in both types employs IMA (Interactive Multimedia Association) 4:1 compression, based on PCM sampling at 22 kHz. In 2004, the Motion Picture, Broadcasting, and Recorded Sound Division collected a series of nine "enhanced" QuickTime movies produced by BMW (formerly available at http://usa.bmwfilms.com/), with the main video object in the form of QTV_Sorenson. |
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| LC preference | Regarding video: for compressed instances, bitstreams that conform to or approximate MPEG-2-422 (4:2:2 Profile) at Main Level (aka MPEG-2 422@ML) or MPEG-2-MP (Main Profile) at Main Level (aka MPEG-2 MP@ML) are preferred to QuickTime. QTV_MJPEG should provide the best quality of the QuickTime video codecs described at this web site. Regarding video: for uncompressed or losslessly compressed instances, which are generally preferred to compressed, QuickTime may be considered as an option, although MXF may be preferred as a wrapper; this topic will be developed in a future investigation. Regarding sound: for file-based compressed instances, AAC_MP2FF or AAC_MP4FF (AAC codec in non-proprietary wrappers) or MP3_FF (MP3 codec in non-proprietary wrapper) are preferred. Regarding sound: for uncompressed or losslessly compressed instances, which are generally preferred to compressed, WAVE_LPCM and/or WAVE_LPCM_BWF are preferred. |
| Disclosure | Fully documented. Proprietary format developed by Apple Computer, Inc. |
|---|---|
| Documentation | File format online HTML specification and downloadable specification, dated March 1, 2001, available as of August 2007. (There 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 the two printings in hand.) For information about the disclosure of information about the bitstreams wrapped by QuickTime, see the descriptions of individual codecs listed under Relationships, above. |
| Adoption | Widely adopted for filemaking. |
| 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 endusers 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 | |
|---|---|
| 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 | Good to very good, given that the options for audio include a wide range from MP3 to LPCM (16 bit word length) formats. See also QTA_AAC and QTA_MP3. Supports various features, e.g., sprites, animation, virtual reality, etc. |
| Tag | Value | Note |
|---|---|---|
| Filename extension | mov, qt |
For movie files. |
| Filename extension | m4p, mp3, [others?] |
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 Apple Developer still image page. |
| 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 | See note. | 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 |
From Gary Kessler's File Signatures Table. |
| 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, p. 92 or p. 96.1 |
| Mac OS file type | See note. | Audio type tag (QuickTime). Four-character codes that vary according to the audio codec selected; see the QuickTime File Format, pp. 102-03 or pp. 107-9.1 |
| General | |
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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 2007) 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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