You can record the call using API or XML and the suggestions to record calls are as follows.
To record the call in either Mp3 or Wav:
If you want to record the call in Mp3 format or Wav format, all you have to do is change the file_format as Mp3 or Wav as per your requirement.
To record the call in either stereo or mono:
You can record a call either in mono using API or stereo using XML.