Data Recording Formats

Data can be recorded in HGL native format and/or DATX format. This is configurable, independently for each channel, in the channel configuration screen, “Recording formats” tab:

HGL File format

The HGL native file format used is not multiplexed; therefore each channel is recorded in a separate file. User events inserted during the recording will be inserted in the raw file, and the same for gain changes that will affect the conversion from raw ADC to EUs. In the HGL file format,  the raw ADC integer values coming from the acquisition card are recorded to disk (in 16 bits or 24 bits). The calibration information (to convert the ADC into engineering units) is stored in the file header. So if the calibration information used during the recording are erroneous for any reason, it is always technically possible afterwards to edit the raw file header and change the calibration later on.

There is a maximum limit for a raw file size, which is not a setting that can be modified via the Hawk GUI, but is configurable (as a duration in minutes) in the INI file of the Hawk acquisition engine. Once the hawk has reached the maximum limit for a file, it will close it, and open a new one, without loss of any data samples.

DATX file format

The DATX file format is multiplexed; there are various settings available to tailor it to the user’s requirements. Those are editable in the “Recording” tab of the Preferences screen:

• Multiplexed: if ticked, each Hawk acquisition engine will regroup channels by common sample rate and sample resolution, with a maximum of 32 channels per group. Each group of channel will be recorded in a separate file. If unticked, each channel is recorded in a separate file.
• File duration in seconds
• Insert files in the database: if ticked, the DATX files will be inserted in the HGL database (the HGL files are always inserted), and therefore managed by the HGL system (see chapter 0 – Disk space management). If unticked, the DATX files generated will be left in the Hawk acquisition engine output folder, to be managed by the user.
• 16 bits always: will force the DATX to be recorded in 16 bits, while the data might be recorded in HGL format in 24 bits.
• Pack channels: if ticked, any gap in the channel configuration will be filled in with dummy channels. Those dummy channels are applied only in the context of the DATX recording, the data will be padded with zeroes in the DATX file for those dummy channels.
• Index file generation: the DATX file format comprises the numeric data file(s), and a text-based index file. It is possible to generate one index file per file set (a new file set is created when we reach the file maximum duration), per segment (i.e. per writing), or not generate any index file.