In the SDK, the function call for playdate.sound.fileplayer.new(..) does not state what the buffersize defaults to if not specified.
The nearest thing to this is that in the description for playdate.sound.fileplayer:play(...) it mentions "creating and filling a 1/4 second playback buffer if a buffer size hasn’t been set yet". If this is in fact the default, it would be nice to have it stated in the description of new()... ie:
If given, buffersize specifies the size in seconds of the fileplayer’s data buffer, or else an 0.25 second buffer will be used.