Re: [Discuss-gnuradio] QT GUI Range response (GNU radio companion)

[Derek Kozel]

Hi Jan,

You've found the right place to ask. The IRC/Slack channel is also a 
good resource for talking to people.

Usually when delays are that long it's a sample rate issue. The 
underlying cause is that each block has some buffers so there's always a 
latency from input to output of sample period * total buffer length. At 
tens of megasamples per second that's not very much delay, but at lower 
rates, such as the audio rate you're probably using, that can be 
appreciable fractions of a second. You're describing multiple seconds 
which usually means there's a sample rate mismatch that's causing 
buffers to completely fill and back pressure the entire flowgraph. Do 
you notice the delay increasing over time?

That's about as far and specific as we can guess without seeing your 
flowgraph. Can you post your GRC file here for us to take a look at? 
That's the best although there's also a screenshot feature in the GRC 
menu. If you want to post a screenshot please host it somewhere else 
(like imgur) and link to it to keep the email size small.

Cheers,
Derek
MW0LNA

On 4/16/2019 10:06 AM, Jan Simons wrote:
> Hello,
> I just joined this group so hope my question fits this group.
> I started with GNU radio companion a few month ago. Have been using 
> Matlab/Simulink for about 15 years for DSP.
> Use it e.g. for ham radio shortwave noise cancelling and noise reduction.
>
> I am using the widget QT GUI range in my models for changing settings.
> What I have noticed is that a change in the setting is delayed by 
> several seconds when the value is passed through an other block e.g. a 
> multiplier or transcendental block . Even if I remove all not relevant 
> processing.
> So a change takes a few seconds to have an effect.
>
> Have googled a lot but cannot find a hint.
>
> Am I doing something wrong?
> How can I improve the response time?
>
> Thanks,
> Jan PA0SIM
>
>
>
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