[
https://issues.apache.org/jira/browse/TIKA-4060?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17730315#comment-17730315
]
Gregory Lepore commented on TIKA-4060:
--------------------------------------
I'm not 100% sure, but I think the offset is incorrect for the ID3 version of
the magic. The ID3 header can be anywhere from 0-2045 total bytes, after the
494433, so the offset of the
FF(F0|F1|F8|F9)(40|41|44|45|48|49|4C|4D|50|51|54|55|58|59|5C|5D|60|61|64|65|68|69|6C|6D|70|71|80|81|84|85|88|89|8C|8D|90|91|94|95|98|99|9C|9D|A0|A1|A4|A5|A8|A9|AC|AD|B0|B1)(00|01|20|40|41|60|80|81|60|A0|C0|C1|E0)
values can be anywhere from 3 to 2049 (I think that's right).
I would try sneaking up on it by matching the offset to the exact values in
your test files and then worrying about the full range of possible offsets. I
often build up my signatures that way.
If the above doesn't work, I can work on figuring out the Tika mimetype meaning
of offset="512:2048". The PRONOM equivalent is the value in the curly braces,
in this case the \{0-2045} means the subsequent values can appear anywhere from
0 to 2045 bytes after the 494443.
Does that make sense?
> Add magic to audio/aac in tika-mimetypes.xml
> --------------------------------------------
>
> Key: TIKA-4060
> URL: https://issues.apache.org/jira/browse/TIKA-4060
> Project: Tika
> Issue Type: Sub-task
> Reporter: Gregory Lepore
> Priority: Minor
> Attachments:
> 067aece423d8694a891a61a45ac0e870914bc1314ef510ac40b36ca3397843ef,
> cb1bec08898db7a733b42ac44bdd76b6177cd3a07a2435a83fd99b7453d564d1
>
>
> Currently tika-mimetypes only recognizes audio/aac files by the file
> extension. PRONOM recently added support for identifying aac files, but the
> signature is tricky. There are two signatures, below in PRONOM format curly
> braces mean to look ahead between the two values for the subsequent patterns.
>
> The first pattern is pretty basic, the second pattern is the first pattern
> after a 2048 ID3 header.
>
> ||Name|Audio Data Transport Stream sig.1|
> ||Description|An FF pattern from BOF with variation of byte stream|
> ||Byte sequences|
> ||Position type|Absolute from BOF|
> ||Offset|0|
> ||Maximum Offset|0|
> ||Byte order| |
> ||Value|FF(F0\|F1\|F8\|F9)(40\|41\|44\|45\|48\|49\|4C\|4D\|50\|51\|54\|55\|58\|59\|5C\|5D\|60\|61\|64\|65\|68\|69\|6C\|6D\|70\|71\|80\|81\|84\|85\|88\|89\|8C\|8D\|90\|91\|94\|95\|98\|99\|9C\|9D\|A0\|A1\|A4\|A5\|A8\|A9\|AC\|AD\|B0\|B1)(00\|01\|20\|40\|41\|60\|80\|81\|60\|A0\|C0\|C1\|E0)|
> |
> ||Name|Audio Data Transport Stream sig.2|
> ||Description|ID3 tag variation with variable byte stream|
> ||Byte sequences|
> ||Position type|Absolute from BOF|
> ||Offset|0|
> ||Maximum Offset|0|
> ||Byte order| |
> ||Value|494433\{0-2045}FF(F0\|F1\|F8\|F9)(40\|41\|44\|45\|48\|49\|4C\|4D\|50\|51\|54\|55\|58\|59\|5C\|5D\|60\|61\|64\|65\|68\|69\|6C\|6D\|70\|71\|80\|81\|84\|85\|88\|89\|8C\|8D\|90\|91\|94\|95\|98\|99\|9C\|9D\|A0\|A1\|A4\|A5\|A8\|A9\|AC\|AD\|B0\|B1)(00\|01\|20\|40\|41\|60\|80\|81\|60\|A0\|C0\|C1\|E0)|
> |
--
This message was sent by Atlassian Jira
(v8.20.10#820010)
