BeginOutput
virtual BSimpleMediaOutput* BeginOutput();
BSimpleMediaOutput* output = sProducer->BeginOutput();
BMediaOutput* output = sProducer->BeginOutput();
BMediaOutput* output = sProducer->BeginOutput();
BMediaOutput* filterOutput = sFilter->BeginOutput();
BMediaOutput* output = sFilter->BeginOutput();
assert(sProducer->Connect(sProducer->BeginOutput(),
sFilter->BeginOutput()) == B_OK);