Re: Sample Rate and audio underflow ....

[Cinaed Simson]

Hi Rob - you should just post the GRC file to the mailing list - just 
attach it to the message.

If the only thing you changed was sampling rate, then you will most 
likely have trouble.

 But you haven't provided enough information in order for anone to help 
you.

Note, the website in the URL appears to be insecure - at least my 
browser claims it's insecure - presumably because it usees http instead 
https.

-- Cinaed

On 5/13/21 1:30 PM, Rob Roschewsk wrote:
> Hi all!
>
> I'm working on a "Hello, World!" flow in GRC .... just a simple NBFM 
> receiver tuned to my local NOAA station.
>
> Using an RTLSDR and the osmocom block ... into a low-pass that 
> decimates by 5 into the NBFM block and then an audio sink. It doesn't 
> get any more simple. Here is a image of the flow 
> http://pabut.org/wiki/images/a/aa/My-fmrcv.grc.png 
> <http://pabut.org/wiki/images/a/aa/My-fmrcv.grc.png>
>
> So with the sampling rate set to 2M .... works fine ..... if I REDUCE 
> the sample rate, say 240k, I start to get audio sink underruns 
> "aUaUaUaUaUaUaUaUaU" and I only get small blurbs of audio.
>
> I'm sure to set the sample rate in the downstream blocks appropriately.
>
> 240k samples/sec should be plenty for a 5khz deviation FM signal ... 
> right??
>
> This is completely counterintuitive to what I was expecting.  I 
> thought by reducing the sample rate I would lower CPU consumption ... 
> and mitigate the exact problem I'm experiencing at the lower rate.
>
> What am I not grocking here??
>
> Thanks,
> --> Rob