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 | ISO/IEC 15444-3:2002/Amd.2:2003. Information technology -- JPEG 2000 image coding system -- Part 3: Motion JPEG 2000/Amendment 2: Motion JPEG 2000 derived from ISO base media file format (formal name) Motion JPEG 2000 file format (common name) |
| Description | Object-oriented file wrapper based on ISO_BMFF, designed for time-based audio-visual information, including video, audio, and other tracks. (See Notes for additional information.) Some elements that are part of a content presentation may also be outside the file and incorporated by reference. In contrast to the temporal or inter-frame compression found in formats like MPEG-2, MPEG-4_V, and MPEG-4_AVC, MJP2 frames are represented as separate entities encoded with J2K_C (lossy or lossless). Comments from specialists indicate that image data may take the form of codestreams (sometimes called .j2c files) or fully realized JPEG 2000 (Part 1) files (.j2p). In the former instance, additional metadata pertaining to things like color space may have to be added to the file; comments welcome. The standard permits creators to declare profiles for MJP2 files and specifies the Motion JPEG Simple Profile (p. 9), summarized in the Notes below. |
| Production phase | Generally used for middle- and final-state archiving or end-user delivery. |
| Relationship to other formats | |
| Subtype of | ISO_BMFF, ISO Base Media File Format |
| Has subtype | MJP2_LL, Motion JPEG 2000 File, with Lossless Compression |
| Has subtype | MJP2_LSY, Motion JPEG 2000 File, with Lossy Compression |
| LC experience or existing holdings | None |
| LC preference | No preference has been established for video wrappers. Discussion in the Motion Picture, Broadcasting, and Recorded Division during 2004-06 has suggested that losslessly compressed JPEG 2000 frame images would be a good encoding option for reformatted video. Wrapper alternatives for these images and accompanying audio include MXF, AAF_1_1, and MJP2_FF (this page). Encoding preferences for file-based lossy compressed video are less clear, but there is interest in 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). These may also be wrapped in MXF, AAF_1_1. The investigation of options continues. |
| Disclosure | Open standard. Developed jointly by the Motion Pictures Expert Group (MPEG), a working groups within the ISO/IEC committee structure formally known as ISO/IEC JTC 1/SC 29. |
| Documentation | ISO/IEC 15444-3:2002/Amd.2:2003. Information technology -- JPEG 2000 image coding system -- Part 3: Motion JPEG 2000/Amendment 2: Motion JPEG 2000 derived from ISO base media file format. |
| Adoption | Increasing interest in 2005-06. During this period, the format received comment in the archiving community; see for example the National Library of Medicine (NLM) Video Archivists 2005 Web site. Examples of adoption in 2006 include Grass Valley's announcement of a SD/HD camcorder with a built-in JPEG 2000 codec, and BroadMotion's announcement of JPEG 2000 and Motion JPEG 2000 codecs optimized for a pair of Texas Instruments digital signal processors. |
| Licensing and patent claims | See ISO_BMFF |
| Transparency | Depends upon the encoding within the file; see J2K_LL and J2K_LSY. |
| Self-documentation | The structure includes boxes and headers that contain the technical metadata needed to manage the media streams. Boxes may be added by implementers; the cited description of a digital cinema profile adds an MPEG-7 descriptive metadata track. |
| External dependencies | None. |
| Technical protection considerations | See ISO_BMFF |
| Video elements | |
| Normal rendering for video | Good support. The format supports timescales that manage the playout of time-based media streams and hint tracks employed in streaming applications. |
| Clarity (support for high video image resolution) | Excellent, especially when frames are compressed with J2K_LL encoding. For J2K_LSY encoding, the outcome will depend on the type and extent of compression, and the encoder used. |
| Functionality beyond normal video rendering | The specification discusses features like composition (the mixing or matrixing of tracks), random access, and fragmented movie files. |
| Sound elements | |
| Normal rendering for sound | Good support. |
| Fidelity (support for high audio resolution) | Excellent; the format supports LPCM encoding (as "raw" or "twos-complement" data) with no stated limit on sampling or bit depth. The simple profile, however, is limited to a single audio track, not to exceed 48 kHz and 16 bits. The format also supports tracks using any encoding specified in MPEG-4; for information, see MP4_FF_2. |
| Support for multiple sound channels | The support for multiple tracks permits the use of multiple audio streams and/or individual streams encoded in structures like 5.1 (e.g., AAC_MP4 from the MPEG-4 family). |
| Functionality beyond normal sound rendering | See beyond-normal-rendering note in the video section above. |
| Tag type | Value | Note |
| Filename Extension | mj2, mjp2 | From the specification; mj2 is preferred. |
| Internet Media Type | video/mjp2 | From http://www.faqs.org/rfcs/rfc3745.html. |
| Magic numbers | 12 byte string: X'0000 000C 6A50 2020 0D0A 870A' | "For all JPEG-2000 family files," including MJP2, from http://www.faqs.org/rfcs/rfc3745.html |
| File type brand | mjp2 | In the ISO_BMFF file type box, "indicates unrestricted conformance to this specification," from Annex A of the specification. |
| File type brand | mj2s | In the ISO_BMFF file type box, "indicates indicates the simple Motion JPEG2000 profile [see Notes below]," from Annex A of the specification. |
| General | (1) About usage: some commentators are careless about their use of the term Motion
JPEG 2000 and readers should take care to distinguish discussions
of JPEG 2000 frames wrapped according to the specification described here
from descriptions of other wrapping options, e.g., AVI
or MXF. Specialists indicate that there are no plans to develop an MXF wrapping for Motion JPEG 2000; turns of phrase that conjoin MXF and Motion JPEG 2000 are likely to mean MXF wrapping JPEG 2000 frames, i.e., MXF_JP2 (SMPTE specification 422M, as seen in DCP_1_0).
(2) Quoted from the specification Annex B: In the file format, the overall presentation is called a movie. It is logically divided into tracks; each track represents a timed sequence of media (frames of video, for example). Within each track, each timed unit is called a sample; this might be a frame of video or audio. Samples are implicitly numbered in sequence. Note that a frame of audio may decompress into a sequence of audio samples (in the sense this word is used in audio); in general, this specification uses the word sample to mean a timed frame or unit of data. Each track has one or more sample descriptions; each sample in the track is tied to a description by reference. The description defines how the sample may be decoded (e.g. it identifies the compression algorithm used). Unlike many other multi-media file formats, this format, with its ancestors, separates several concepts which are often linked. Understanding this separation is key to understanding the file format. In particular: • The physical structure of the file is not tied to the physical structures of the media itself. For example, many file formats 'frame' the media data, putting headers or other data immediately before or after each frame of video; this file format does not do this. • Neither the physical structure of the file, nor the layout of the media, is tied to the time ordering of the media. Frames of video need not be laid down in the file in time order (though they may be). This means that there are file structures which describe the placement and timing of the media; these file structures permit, but do not require, time-ordered files. All the data within a conforming file is encapsulated in boxes (called atoms in the other versions of this file format [i.e., QuickTime]). There is no data outside the box structure. All the meta-data, including that defining the placement and timing of the media, is contained in structured boxes. This specification defines the boxes. The media data (frames of video, for example) is referred to by this metadata. The media data may be in the same file (contained in one or more boxes), or can be in other files; the meta-data permits referring to other files by means of URLs. The placement of the media data within these secondary files is entirely described by the meta-data in the primary file. They need not be formatted to this specification, though they may be; it is possible that there are no boxes, for example, in these secondary media files. Tracks can be of various kinds. Three are important here. Video tracks contain samples which are visual; audio tracks contain audio media. Hint tracks are rather different; they contain instructions for a streaming server in how to form packets for a streaming protocol, from the media tracks in a file. Hint tracks can be ignored when a file is read for local playback; they are only relevant to streaming. (p.28) (3) Quoted from the specification Annex B: The Motion JPEG 200 Simple Profile includes the following elements: • Exactly one video track is present. • At most a single audio track, using only 8 or 16-bit raw audio, is present. • Each track shall have exactly one sample description, used by all samples. • The sample rate of the audio, if present, shall not exceed 48 kHz. • The frame rate of the video shall not exceed 30 frames per second. • The video codestream profile shall be profile O for both the motion sequence and the still image, if present. • The file is self-contained; no data references are used, and therefore all media data is contained within the single file. • The media data in the Media Data Box(es) is placed within the box(es) in temporal order. • If more than one track is present, the media data for the tracks is interleaved, with a granularity no greater than the greater of (a) the duration of a single 'sample' (in file format terms) or (b) one second. • The transformation matrices used are restricted to uniform scaling and rotation by multiples of 90 degrees. Although not a formal profile, some provocative profile-like ideas pertinent to video reformatting projects are articulated in the straw man documents available from the National Library of Medicine (NLM) Video Archivists 2005 Web site. |
| History | The underlying ISO_BMCC format and this subtype owe a strong debt to Apple's QuickTime. |
URLs
Print
• ISO/IEC 15444-3:2002/Amd.2:2003. Information technology -- JPEG 2000 image coding system -- Part 3: Motion JPEG 2000/Amendment 2: Motion JPEG 2000 derived from ISO base media file format.
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