The „.json“-fileformat is a human readable object oriented format, mainly usful for import/export. The fileformat is not very compact, so you can expect very big files and it is time consuming to work with them.

{ 
  "trial": {
     "frames": [{},{},...],
     "phases": [{"name": "RStride", "start": 100, "end": 200},...]
  }
}

At the time not all informations saved in a trial are exported into Json-files. Missing parts can be added esay if needed.