Re: Latency due to hardware initialization

[Fabian Schwartau]

Hi Ahmad,

I think both, sink and source, start consuming/producing samples as fast 
as they can. If the buffer for a hardware sink runs empty, you will get 
"U"s printed in the command line, for under-run. If a buffer after a 
hardware source runs full, you will get "O"s printed, for over-run.
If nothing is printed, no samples will get lost and each block runs as 
fast as it can.
Also check out this tutorial on sample rates, which explains this in 
more detail:
https://wiki.gnuradio.org/index.php?title=Sample_Rate_Tutorial

Best,
Fabian

Am 25.04.23 um 08:23 schrieb Ahmad Oweis:
> Hi all,
>
> I'm investigating the factors behind the latency in my simple GRC flow 
> graph, I have a theory and I'd be grateful if someone can confirm it or 
> refute it.
>
> Say I have a simple flow graph consisting of a file source connected to 
> a hardware sink.
>
> My understanding: when I run the flow graph, the source starts producing 
> samples and storing them in the buffer. In the meantime, the hardware 
> sink is initializing (loading FPGA, etc.). Once the hardware is ready to 
> transmit samples, it starts consuming from the buffer. 
> This initialization delay adds to the overall system latency. Is this 
> correct? or does the source only start producing samples after the 
> hardware is initialized?
>
> If my understanding is correct, how can we avoid this delay? Is there a 
> way to ask the file source to wait until the hardware is ready and then 
> start sending samples?
>
> Thank you
> --
> Ahmad Oweis