Determine maximum length of recording according to browser- and DB-capabilites

[kyro46]

The buffer for recordings in the browser might be a limit for the length of recordings.

• Do browsers stop a recording if a not yet determined limit/buffer is reached?
• What is the default value?
• How long can be recorded before reaching this limit? One might want to address the different encodings in different browsers. For fairness, the lowest value shall be used.

The DB might encounter problems with very big recordings, as they are saved as base64-blob.

• Is it a good idea to store this type of data in the db?
• How long can be recorded before writing to the db might get problematic? One might want to address the different encodings in different browsers.
• If stored as files, one has to consider delete, copy, import and export etc. of course.

[kyro46]

DB can store up to 4GB per answer - no problem there despite performance.

[kyro46]

The recordings produce around 10KB per second. With lots of participants and long recordings, this might put some stress on the DB.

Since it is unclear whether all DB-installations can handle this amount of data in (large scale) assessments, it might be better to save the recording to the filesystem.

[kyro46]

Files are stored in the filesystem as of d5c4dcb.
The size of recordings is noted in the readme to give a hint to admins how much storeage usage can be anticipated and a link to check the supported browsers is provided as of f13702c.