PicoQuant GmbH HydraHarp 400 Software V. 3.0.0.1
8.2. Data File Formats
While for many purposes the ASCII export of histograms to files or to the clipboard is sufficient and easy, you
also may want to access the HydraHarp data files via custom programs. This section provides only a brief
overview on the file format. For details please refer to the online help file available via the help menu.
To overcome certain limitations of the formats used in the past, the latest HydraHarp software uses a new file
format previously proven in our SymPhoTime 64 software. It is designed to be future poof in the sense that files
created by the current software version stay valid for future software revisions and, moreover, files created by
future software versions will most likely still be readable by older software, although they might contain
information, that software can't even "know" about. This is achieved by using a tagged format. Tags identify the
data to follow, and give the type, length and even meta information. The exact location of an individual item in
the file is then irrelevant. Version robustness is granted as long as version-breaking changes to the semantics
of a given field are implemented by a tag with a new identifier rather than expanding the range or interpretation
of the old one. The list af tags (identifiers) and their interpretation rules can be kept in a tag dictionary. With this
as a precondition, the software only has to show tolerance on missing non-mandatory (i.e. optional) content.
The new format definition unifies PicoQuant's existing file formats which individually evolved over many years.
The resulting new TTTR file format with the extension *.ptu will be used for all current and future TCSPC
products supporting TTTR mode and enriches them by powerful new features. Similarly, a tagged file format
with the extension *.phu will cover the histogram data formats of our current and future TCSPC products.
The new format may at first glance look more complicated than previous versions with hard coded structure.
Nevertheless, we hope that the benefits of version tolerance and “durability” will outweigh the complications. To
support understanding of the format and implementation of custom software acessing these files, a set of
demos is provided in the subfolder \Filedemo in your chosen installation folder. If you need to evaluate
more header items than the demos do, please refer to the HydraHarp online help file available via the help
menu. A file format related html help file is also provided in the file demo folder. It contains a list of tag types
and a tag dictionary that explains the individual items. Note that the dictionary contains more items than the
HydraHarp software actually uses. It is recommended to go by a specific file, have one of the demos read it
and then look at the list of header items you get. You can also use the PicoQuant File Info shell extension that
will be installed by the HydraHarp software setup to inspect individual header items of a *.ptu or *.phu file.
Just right-click on the file in Windows explorer and select Properties.
For backward compatibility version 3.0 of the HydraHarp software can still read old files of format version 2.0
(*.hhd, *.ht3). Note, however, that saving such files converts them to the new format. Despite the intended
version tolerance of the tagged format, for consistency and safe version checking the new HydraHarp data
files still carry a format version number, which is now called content version and currently has the string value
“3.0”. In order to identify a HydraHarp data file as a file created by and to be used by the native HydraHarp
software there is a tag assured content which begins with the string “HydraHarp“. There is also a pair of tags
creator name and creator version that identify the creating software. Programmers of custom software writing
such files MUST USE THEIR OWN CREATOR NAME.
Note that despite our best efforts towards version tolerance, file formats in future software releases are subject
to change without notice.
8.2.1. Interactive Histogramming Mode File Format
The standard HydraHarp histogram data files created by the HydraHarp software in interactive histogramming
mode (*.phu) are tagged binary files which contain both the setup parameters and the actual histogram data.
The latter can be present multiple times, i.e. multiple measurements can be stored in one file. Relevant settings
are stored for each meaurement separately. In order to identify a HydraHarp data file as a file created by and to
be used by the native HydraHarp software, a program reading in these files can read the tag assured content
which begins with the string “HydraHarp“. However, a piece of software aiming solely at retrieving the
histogram data content can (and should) be tolerant about this tag and go for the pure histogram data. This
tolerance will ensure compatibility for the future. Indeed, the demos in the subfolder \Filedemo in your
chosen installation directory are following this tolerant approach. For more information on individual file tags
and their content, please consult the online help file available via the help menu.
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