Change preferences

The preferences window allows you to configure various settings used by DROID after it has started up.  There are also some settings which control how DROID starts up, which are not configured through this window. There are three main tabs in the preferences window:

• Profile Defaults
• Signature Updates
• Export Defaults

The Profile Defaults tab contains the settings used when creating a new profile. 

• Binary Signature File
• Container Signature File
• Analyse contents of archive files
• Generate MD5 hash for each file
• Maximum bytes to scan
• Match extensions if no other signatures defined
• Match extensions against all known extensions
• Default throttle

Binary Signature File

The binary signature file is the version of the binary signatures to use when trying to identify file formats.  Binary signatures are patterns to find inside the file in order to identify its file format.  Once a profile has been created, you cannot change the binary signature file it uses.  It is recorded with the profile when you save it.

Container Signature File

The container signature file is the version of the container signatures to use when trying to identify file formats.  Container signatures identify file formats by looking for embedded files inside the main files.  Binary signatures can be applied to these embedded files.  This improves the accuracy of recognition for these types of file formats, as the search is confined to the specified embedded files, not to the entire containing file.  Once a profile has been created, you cannot change the container signature file it uses.  It is recorded with the profile when you save it.

Analyse contents of archive files.

If this option is checked, then DROID will look inside zip, tar and gzip files and profile the files it finds inside them.

Generate MD5 hash for each file

If this option is checked, then DROID will produce an MD5 hash for the content of the file.  By default this option is off, as generating hashes slows down profiling significantly.  Read "Detecting duplicate files" for more information on why you may want to generate hashes.

Maximum bytes to scan

When DROID is trying to identify files, it looks inside the files for common patterns. This setting allows you to configure how far from the beginning or end of the file DROID will scan before it stops trying to identify the file. This has a large effect on the performance of DROID, and a smaller effect on the accuracy of its identifications.

Almost all patterns which identify the format of files are found fairly close to the start or end of the file. By default, this setting is 65536 bytes (64KB).  You can make it smaller, and DROID's performance will increase, but the accuracy of identifications may go down.  Alternatively, you can make it bigger, and the performance of DROID will go down, and the identification accuracy may go up. 

Setting this value to a negative number (e.g. -1), will cause DROID to scan the entire file (possibly more than once, if different patterns trigger those scans).  This setting gives the maximum possible accuracy DROID can achieve, but can cause DROID to profile very slowly, particularly if you have large files.

If you do have files which are not being identified, you can increase this value, or set it to -1, to see if this has any effect on identification accuracy.  If it still can't identify those files on a large setting (or the unlimited -1 setting), then you should probably choose a smaller value to increase the identification performance.

Match extensions if no other signatures defined

If this option is selected, DROID will only attempt to match file extensions for formats for which no other binary or container signatures are defined.  The thinking here is that, if a presumably more accurate signature failed to match the file format, then matching against the extension alone would give potentially misleading results.  This is the default behavior,  and is the same as previous versions of DROID.

Match extensions against all known extensions

If this option is selected, DROID will attempt to match a file extensions against all known extensions.  This may be helpful if you find you have files in newer formats, for which there is currently no good binary or container signature, or you have unusual files for which the existing signatures fail to match.  Using this option will produce identifications for more files, and more multiple identifications for files.  

Default throttle

This is the delay in milliseconds that DROID should pause between identifying files read from the file system.  Specifying a higher delay will cause DROID to work slower, placing less load on your computer, network or disk storage.  It does not cause a pause between identifying files inside archival files.  

Unless you need to slow DROID down, this should be set to zero.  Unlike the other profile preferences, this value can be dynamically adjusted while running using the throttle slider control on the main window.  The throttle setting can be different for each profile, and will be saved with the profile.

This tab allows you to configure where DROID should try to update its signatures from, and how often.

• Binary Signatures URL
• Container Signatures URL
• Proxy settings
• Automatically check for updates
• Update settings
• PUID URL pattern

Binary Signatures URL

The web address where DROID can find a PRONOM-compatible web service to download binary signature updates.

Container signatures URL

The web address where DROID can find the container signature file.  Container signature files do not require specialised PRONOM web services to download from - a file available on a standard web server is sufficient.

Proxy settings

Clicking this button will allow you to configure network proxy settings if your network has a proxy.  Please consult your network administrator for details of any proxy settings you may need to make.

Automatically check for updates

If this box is checked, then DROID will automatically attempt to look for updated signatures according to the schedule you specify:

Update settings

• Every time DROID starts up - DROID will try to check for signature updates when it starts.
• Every X days - on starting up, DROID will check for signature updates after the number of days since the last check.  Note that if you leave DROID running for more days than is specified, it will not automatically try to update its signatures.  The check is still only made on startup, but only if the number of days since the last time it checked has elapsed.
• Prompt before downloading - If this box is checked, DROID will prompt you before downloading new signatures.
• Use updated signature files by default - If this box is checked, DROID will automatically use a newer signature file by default.  If it isn't checked, it will still download the file, so it is available for selection in the profile default tab, but it will not automatically make it the default signature file to use.

PUID URL pattern

The PUID URL pattern is the web location which DROID will connect to when clicking on a PUID hyperlink in the profile tab.  This should contain the URL to connect to, and the place into which the PUID should be inserted is indicated by %s.  For example, if we were to click on a hyperlinked PUID of "fmt/111" in the main profile results, DROID would launch your web browser at the address: "http://www.nationalarchives.gov.uk/pronom/fmt/111".

The Export Defaults tab contains miscellaneous settings, to configure how DROID exports CSV files by default.

• Default CSV export options

Default CSV export options

DROID can export profiles to CSV files in two ways: one row per file, and one row per format.  See exporting profiles for more information on each of these options.  The settings here only configure the default for export.  When you export, you can select which you prefer on a per-export basis.