Re: Latency due to hardware initialization
On 25/04/2023 11:46, Ahmad Oweis wrote: Thanks Marcus. I'm getting latency in the range of seconds, and this was the only way I could explain it.. Is this mentioned anywhere in the documentation? How can I learn more about the scheduler operation? Thanks, How are you measuring latency? Do you mean: "from the time I start the program to the time signals start coming out of my radio"? In that case, yeah, it takes a non-trivial amount of time to get the radio initialized, and Gnu Radio cannot possibly start sending samples until it is initialized. On Tue, 25 Apr 2023, 17:23 Marcus D. Leech, wrote: On 25/04/2023 02:23, Ahmad Oweis wrote: 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 Gnu Radio doesn't start running the graph until all the blocks in it are initialized--that includes hardware source/sinks.
Re: Latency due to hardware initialization
Thanks Marcus. I'm getting latency in the range of seconds, and this was the only way I could explain it.. Is this mentioned anywhere in the documentation? How can I learn more about the scheduler operation? Thanks, On Tue, 25 Apr 2023, 17:23 Marcus D. Leech, wrote: > On 25/04/2023 02:23, Ahmad Oweis wrote: > > 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 > > Gnu Radio doesn't start running the graph until all the blocks in it are > initialized--that includes hardware source/sinks. > >
Re: Latency due to hardware initialization
On 25/04/2023 02:23, Ahmad Oweis wrote: 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 Gnu Radio doesn't start running the graph until all the blocks in it are initialized--that includes hardware source/sinks.
Re: Latency due to hardware initialization
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
Latency due to hardware initialization
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
