Data Stores Have Different Durations

Tech Note: TN0957
Product: TTankX, OpenEx, RS4, Synapse
Version: All
Date Added: 2015-09-02


When comparing different data elements saved with the TDT system you may see different total recorded lengths. The TDT data storage methodology emphasizes and guarantees data synchronization across all data sampled on a TDT system, independent of sample rate or data format - even across different devices within the system.

In software, continuous data is stored as a timestamp and a chunk of points that starts and remains synchronized, sample for sample, for the entire recording session. You see different total recorded lengths on different data elements saved with the TDT system because the data Stores are saved to the tank in evenly sized chunks and only full chunks are written. This chunk size is user settable or set automatically in software depending on the sampling rate. By default, chunk sizes run anywhere from 100 ms to 500 ms. For example, the default chunk size is 2048 samples when sampling at 24414.0625 Hz. You can see the exact chunk size in the Storage Specification table when Workbench is in 'Idle' mode, under 'Store Description'.

When recording ends, sampling stops, and any incomplete chunks are not saved to disk. The start time for each store will always line up precisely, but the recorded duration of each data store will likely be different.

The RS4 works differently. Data is saved sample-by-sample while the software is recording, so its chunk size is effectively one and thus it will always have more data than stores with 'chunked' data.

All data across the tanks and RS4 will be synchronized from the onset of the recording, but each store might have a different recorded duration.

Here is a graphical depiction of what is happening: