NAME
Image::MetaData::JPEG::MakerNotes - This document contains random information and details on MakerNotes; it is an appendix to the main manual page of the Image::MetaData::JPEG module, which the reader should refer to for further details and the general scope.
On the problem of MakerNote corruption and ways to overcome it
A widespread problem with Exif maker notes is that there is no common standard for how to parse and rewrite the information in the MakerNote data area. This is the reason why most programs dealing with Exif JPEG files corrupt the MakerNote on saving, or decide to drop it altogether (be aware that there existed programs known to hang when they try to read a corrupt maker note).
In fact, many maker notes contain a non-standard IFD structure, with some tags storing file offsets (see the documentation page describing the IFD structure). Therefore, saving a maker note without regard for internal offsets' adjustment reduces the note mostly to garbage. Re-dumping a maker note after changing the Exif APP1 segment endianness incurs the same problem, because no internal byte-swap is performed.
A few countermeasures have been introduced in this package to try to cure some maker note problems. The first one concerns the correct byte order (the endianness, which is not always the same used in the Exif segment), which needs not to be known in advance; it is in fact determined by using the fact that, if the note is IFD-like (even non-standard), the number of tags is always in the range [1,255], so the two-bytes tag count has always the most significant byte set to zero, and the least significant byte set to non-zero.
There is also a prediction and correction mechanism for the offsets in the interoperability arrays, based on the simple assumption that the absolute value of offsets can be wrong, but their differences are always right, so, if one can get the first one right ... a good bet is the address of the byte immediately following the next_IFD link (or the tag list, if this link is absent). If the parsing process does not end successfully, this mechanism is enabled and its "corrected" findings are stored instead of the original ones if it is able to cure the problems (i.e., if the second try at parsing the note is successful).
Pieces of information available after parsing the MakerNote
The result of the process of parsing the maker note is stored in a directory in the internal data structure for the APP1 Segment, whose path is "IFD@SubIFD@MakerNoteData_$format", where $format is the specific note format; the 'MakerNote' entry in IFD0@SubIFD is then removed. This translation happens always, because there is a catch-all 'unknown' rule for a binary makernote with very broad acceptance rules. The maker note directory contains, in addition, a special subdir with some fields reporting about the parsing process.
key content
-------- -------
ORIGINAL the raw content of the maker note (unparsed)
SIGNATURE the first few bytes which allowed the format to be chosen
ENDIANNESS the byte order chosen during parsing
FORMAT the maker note format chosen during parsing
ERROR [optional] error details, in case of failure while parsingSupported MakerNote formats
Maker note formats are specified in a special internal hash, with a key for each format (including the 'unknown' format). Each format entry corresponds to an anonymous hash containing information for parsing the MakerNote; the "normal" format is considered to be an IFD-like MakerNote with a next_link pointer, offsets counted from the global TIFF header and no MakerNote internal TIFF header.
key meaning or effect
--------- -----------------
signature the MakerNote signature (a regular expression)
maker the Maker signature (i.e., its name, no regex)
tags a reference to a hash for tag translations
(A) mkntstart if set, offsets are counted from the maker note start
(B) mkntTIFF if set, offsets are counted from the internal TIFF header
(C) ignore if set, the format is to be ignored
(D) nonext if set, the maker note IFD does not have a next_link
(E) endianness if set, the byte order is fixed to this value
(F) nonIFD if set, the maker note is not IFD-likeCurrently, "supported" formats are described in the following table; authoritative data is indeed kept in Tables_makernotes.pl, to which the reader should refer for tag definitions and translations. Remember that both the 'signature' and the 'maker' fields are regular expressions matching at the beginning (the real signature corresponds to $1).
A B C D E F Maker Signature
----------- --------- -----------------
Agfa AGFA (AGFA \000\001)
Canon Canon ()
Casio_1 CASIO ()[^Q]
Casio_2 CASIO (QVC\000{3})
Epson EPSON (EPSON\000\001\000)
Foveon FOVEON (FOVEON\000{2}\001\000)
Fujifilm x FUJIFILM (FUJIFILM\014\000{3})
HPackard x Hewlett-Packard (HP)
Kyocera x x KYOCERA (KYOCERA {12}\000{3})
Kodak B x KODAK (KDK INFO[a-zA-Z0-9]* )
Minolta_1 MINOLTA ().{10}MLT0
Minolta_2 Minolta ().{10}MLT0
Konica x Minolta|KONICA ((MLY|KC|(\+M){4})|\001\000{5}\004)
Nikon_1 NIKON (Nikon\000\001\000)
Nikon_2 NIKON ()[^N]
Nikon_3 x NIKON (Nikon\000\002[\020\000]\000{2})
Olympus OLYMPUS (OLYMP\000[\001\002]\000)
Panasonic_1 x Panasonic (Panasonic\000{3})
Panasonic_2 x x Panasonic (MKED)
Pentax_1 x Asahi ()[^A]
Pentax_2 x x Asahi (AOC\000..)
Ricoh_1 x RICOH (Rv|Rev)
Ricoh_2 x RICOH (\000)
Ricoh_3 RICOH ((Ricoh|RICOH)\000{3})
Sanyo SANYO (SANYO\000\001\000)
Sigma SIGMA (SIGMA\000{3}\001\000)
Sony x SONY (SONY (CAM|DSC) \000{3})
Toshiba x TOSHIBA ()
unknown x . ()References
MakerNote format details are not usually released by vendors (well, this is an euphemism: no vendor ever, to my knowledge, released any detail on its format, exception made for Sigma/Foveon). All information used for this package was collected on the Internet (and its reliability is therefore limited) or through personal tests. Some interesting sites are (not an exhaustive list at all):
General: home.arcor.de/ahuggel/exiv2/makernote.html
.....: www.ozhiker.com/electronics/pjmt/jpeg_info/makernotes.html
Agfa: www.ozhiker.com/electronics/pjmt/jpeg_info/agfa_mn.html
Canon: www.burren.cx/david/canon.html
Casio: park2.wakwak.com/~tsuruzoh/Computer/Digicams/exif-e.html
...: www.dicasoft.de/casiomn.htm
Epson: www.ozhiker.com/electronics/pjmt/jpeg_info/epson_mn.html
Foveon: Foveon is the same as Sigma, see Sigma
Fujifilm: park2.wakwak.com/~tsuruzoh/Computer/Digicams/exif-e.html
......: www.ozhiker.com/electronics/pjmt/jpeg_info/fujifilm_mn.html
Kyocera: www.ozhiker.com/electronics/pjmt/jpeg_info/kyocera_mn.html
Kodak: my personal tests with my Kodak DX3900 (not IFD-like)
Minolta: www.dalibor.cz/minolta/makernote.htm
.....: www.ozhiker.com/electronics/pjmt/jpeg_info/minolta_mn.html
Nikon: park2.wakwak.com/~tsuruzoh/Computer/Digicams/exif-e.html
...: www.tawbaware.com/990exif.htm
...: www.ozhiker.com/electronics/pjmt/jpeg_info/nikon_mn.html
Olympus: park2.wakwak.com/~tsuruzoh/Computer/Digicams/exif-e.html
.....: www.ozhiker.com/electronics/pjmt/jpeg_info/olympus_mn.html
Panasonic: www.compton.nu/panasonic.html
Pentax: www.ozhiker.com/electronics/pjmt/jpeg_info/pentax_mn.html
Ricoh: www.ozhiker.com/electronics/pjmt/jpeg_info/ricoh_mn.html
Sanyo: www.exif.org/makernotes/SanyoMakerNote.html
Sigma: www.x3f.info/technotes/FileDocs/MakerNoteDoc.html
Sony: www.ozhiker.com/electronics/pjmt/jpeg_info/sony_mn.htmlAUTHOR
Stefano Bettelli, bettelli@cpan.org
COPYRIGHT AND LICENSE
Copyright (C) 2004,2005 by Stefano Bettelli
This library is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License. See the COPYING and LICENSE file for the license terms.
SEE ALSO
The main documentation page for the Image::MetaData::JPEG module.