MIME Type Registrations for JPEG 2000 (ISO/IEC 15444)
Extracted elements (15)
A distinct MIME type (video/mj2) was created for Motion JPEG 2000 rather than reusing an existing type because MJ2 is a restricted usage of the ISO Base Media File Format shared with MPEG-4/MP4, and a new type is needed to identify this restriction unambiguously.
A file format is optional in ISO/IEC 15444-1 for the codec itself, but is mandatory for the image/jp2 MIME sub-type registration. This ensures that content identified by the MIME type always has a well-defined container structure.
Motion JPEG 2000 is placed under the 'video' MIME branch rather than 'image' because it is always intended to contain a video sequence (with optional audio), making the video/* classification correct even though the codec is JPEG 2000.
For video/mj2, interoperability exists with the broader MPEG-4 community because Motion JPEG 2000 derives from the ISO Base Media File Format, which is also the basis for MP4. Reference software for both formats is available.
Implementations may not be able to handle all defined applications or profiles within JPEG 2000. As a result, a decoder may successfully parse the file but be unable to render the image either partially or in full.
JPEG 2000 files registered under these MIME types are binary and MUST be transmitted in a suitable encoding without CR/LF conversion, 7-bit stripping, or similar transformations; base64 is identified as a suitable encoding.
All JPEG 2000 family files share a common 12-byte magic number: X'0000 000C 6A50 2020 0D0A 870A'. This magic number applies uniformly to image/jp2, image/jpx, video/mj2, and image/jpm.
image/jp2 has no required or optional parameters; it is the responsibility of the implementation to determine the appropriate application and render the image to the user.
image/jpx covers all profiles and extensions building on ISO/IEC 15444-2 (JPEG 2000 Extensions). The file format is defined in Annex M of that standard; the Macintosh File Type Code is 'jpx '.
Registers MIME type image/jp2 for JPEG 2000 still images as defined in ISO/IEC 15444-1 Annex I. The recommended file suffix is 'jp2'; alternative suffix 'jpg2' is also declared.
Registers MIME type image/jpm for JPEG 2000 Compound Image files as defined in ISO/IEC 15444-6. The recommended file suffix is 'jpm'; 'jpgm' is also declared. Intended for compound documents containing scanned and/or synthetic images.
Registers MIME type image/jpx for extended JPEG 2000 still images as defined in ISO/IEC 15444-2 (JPEG 2000 Extensions). The recommended file suffix is 'jpf'; 'jpx' is also acceptable but not recommended for desktop files.
Registers MIME type video/mj2 for Motion JPEG 2000 sequences as defined in ISO/IEC 15444-3. The format is derived from the ISO Base Media File Format and may carry audio in addition to video. Preferred file extension is 'mj2'; 'mjp2' is also declared.
JPEG 2000's extensible structure means future metadata fields could theoretically induce recipient actions and present security risks, but no such capability is defined in the current specification. Encryption, signing, and authentication can use mechanisms defined in ISO/IEC 15444-8 (JPSEC).
The descriptive metadata fields defined in JPEG 2000 do not themselves create additional security risks because they are not used to induce particular behavior in the recipient application. However, some metadata fields may encode IPR protection information whose alteration could constitute an offense under WIPO-based national agreements.