[Discuss-gnuradio] When we combine several streams

[Sachi]

Hi, Matt and Eric

I have a basic problem regarding the flow schedueling
in GNU Radio, especially when we try to combine
several sub-streams using a multiplier or an adder. 
Can we make sure the indexes are still aligned?

For example, suppose I want to implement:
z[n] = x[n] + c * y[n]
Source block A is used to genereate x[1], x[2],
x[3]...
source block B is used to genereate y[1], y[2],
y[3]...
Block C, gr_multiply_const_cc, is used to multiply
y[n], as the constant c.
Block D, gr_add_cc, is used to add the two streams,
the flow graph looks like:
A->D
B->C->D

So my question is, can the scheduling mechanism in GNU
Radio guarantee the index alignment?  I mean, will the
block C introduce any delay, or the two sourced
generating data in different speeds, so that at the
adder D, the index for the two sequence is not aligned
any more, but something looks like:
z[n] = x[n] + c * y[n - 1]??

Another more complicated example is the FM stereo
receiver, after fm-demodulating the input signal, we
need to split the data stream into two, process the
two sub-streams separately (filtering), and recombine
them using an adder and a substractor.  Something
like:
A->B->C->F
A->D->E->F
I am concerned about whether the index is still
aligned at F.  Can we make sure (BC) and (DE)
introduce the same delay?  


Thank you very much, the answer to this is very
important to me, because I am going implement some
complex algorithms. I know the simulink in Matlab
could guarantee this, but I am not sure whether GNU
Radio could gurantee this, especially when we split up
stream and recombine again.

Thanks

Sachi




                
__________________________________ 
Yahoo! Mail 
Stay connected, organized, and protected. Take the tour: 
http://tour.mail.yahoo.com/mailtour.html