Change number of samples from int16 to uint16, as this should
never be negative. Change timestamp from uint64 to int64, as
negative timestamps may one day be necessary.

This should help reduce overheating.

just changed SAMPLES_PER_DATA_BLOCK back to 300, this probably requires
a real bug fix somewhere else, not sure why this is an issue.

that was introduced trying to fix buffer delays
data looks ok now, and there seem to be no accumulating delays

this should be made automatic or at least user-selectable through the
GUI