There are multiple file format options depending on your desired interface for post-processing.
Postprocessing is possible in Python or in MATLAB. For data acquisition, there are multiple software programs to choose from. An overview of the software options is given in this article. To use the acquired data with one of these software options for postprocessing it is needed to convert the file format.
Postprocessing in Python
Postprocessing in Python can be started with both .Poly5 and .xdf files. Both file formats can be transformed into an MNE-Python object. The example scripts in the 'examples_reading_data' folder can be used respectively. Furthermore, in V4 of the TMSi Python Interface, the functionality to transform .Poly5 files to .edf file format is added.
Postprocessing in MATLAB
Postprocessing in MATLAB is possible with .Poly5 files. It is possible to convert this file format into an EEGLab compatible file, by using the example script 'Poly5toEEGlab.m'.
Do you have further questions on this topic?