Re: [Discuss-gnuradio] dynamically changing delay in gr_delay (or history in any gr_block)

[Achilleas Anastasopoulos]

I actually tried using filters to implement the delay and they do NOT
work as expected:

I used "Interpolating FIR filter" with taps equal to (0,)*delay+(1,)
and i didn't see any difference as i was changing the delay parameter
dynamically....


Achilleas

On Tue, Nov 15, 2011 at 3:05 PM, Marcus D. Leech <address@hidden> wrote:
> On 15/11/2011 3:00 PM, Achilleas Anastasopoulos wrote:
>>
>> I made a simple example with a cosine and a delayed version of that
>> going through
>> a multiplier, and observing the output together with a slider that
>> changes the delay dynamically.
>> However i do not see any change (eg, elimination of the dc component
>> when delay ~ pi/2).
>>
>>
>> Looking at the code of the block gr_delay it shows that the delay can
>> dynamically change
>> and this results essentially in a call to set_history() in gr_block.
>> Looking further into the set_history() method, it sets the private
>> variable d_history.
>>
>> The question is: does the dynamic change of history have any effect in
>> gr_block?
>> What happens in the guts of the block when d_history changes?
>> and why don't i see any effect in the example above?
>>
>> thanks
>> Achilleas
>
> I ran into the exact same thing a couple of weeks ago.  It has to do with
> the deep-structure of the schedule, and Jonathan Corgan had
>  indicated he was going to look into it.
>
> The weird thing is that FIR filters do the same thing when you change the
> number of tapes (muck with d_history), but they actually
>  *work* dynamically after you change them.
>
>
>
>



-- 
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Achilleas Anastasopoulos
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