The SlingStudio unit can create and maintain up to seven simultaneous recordings:
… for a total of seven project recordings.
All video is recorded in the MP4 file format.
The SlingStudio unit can record project files to either a USB-3 hard disk, or an SD card.
Note that storage media (SD card or hard disk) do not have to be present if you're just streaming live video. You only need to have storage media inserted in (or connected to) the SlingStudio unit if your project requires the saving of actual files locally.
*Note: The line-in audio stream is an M4A audio recording only; the other six recording types are MP4 files containing both audio and video.