audio timing
audio timing is tested with a simple duration of 4s and an offset value list for
begin of 2s;7s;12s.
Because only the timing is tested, it is not important, whether
the used format OGG is interpreted or not; whether there is
noise or not. The timing is derived using the begin and end
of the audio as syncbases for the begin and end for a rotation
of a blue square. This rotation reference is compared with a
red rotation square behind with the same begin and end using
simple offset values. If something red gets visible, an error is
occured.