Re: [Discuss-gnuradio] USRP1 problem, UHD problem, and one suggestion

[Marcus D. Leech]

>
> By default Gnu Radio now schedules each block in its own CPU thread. So
>   
>> there could be
>>   differences in instantaneous latencies down each path.
>>
>>     
> Also- whether a data is processed at the same time in terms of physical
> timeslices in the real world isn't so important, but by definition,
> gnuradio should assure that samples in various block arrive in order to
> the various things- so say in the simplest case you have a vector source
> with [1, 0] in it, and you have two sink blocks connected to it, each
> sink should receive 1,0,1,0 always. Make it more complicated, add a
> const multiplier (*2) in one of the two paths- one sink should receive
> 2,0,2,0... and the other should receive 1,0,1,0. My point is - in-order
> processing and sample order preservation and arrival should be preserved
> or half the DSP in done in gnuradio wouldn't be possible. The Scope sink
> should be grabbing the same number of samples off each of the inputs on
> each work pass, and if one path doesn't have enough available it should
> stop short and not report consuming anything past the smallest available
> number of samples on the inputs, and not render any data seen past the
> shortest available.
>
>   
I'm not sure how the scope sink deals with the "minimum amount of data
available" issue.

But the broader question becomes something like:

   given two (or more) subgraphs where the signals in the subgraphs had
relative phase "foo" at the
   head of those sub-graphs, and the two (or more) subgraphs do
different numbers and types of
   "things" to those signals, is relative phase preserved as seen by a
sink object?

It seems, on reflection, that unless those things *explicitly* modify
phase, then phase should
  naturally be preserved.  This is in stark contrast to the analog
world, where there will be
  minor (or major!) phase-distortions as a result of following different
paths.


-- 
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org