[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Discuss-gnuradio] question about overruns with simple flowgraph

From: Stephen
Subject: Re: [Discuss-gnuradio] question about overruns with simple flowgraph
Date: Mon, 05 Aug 2013 20:48:10 -0500
User-agent: Mozilla/5.0 (Windows NT 5.1; rv:17.0) Gecko/20130509 Thunderbird/17.0.6

On 8/5/2013 8:17 PM, Marcus D. Leech wrote:
> On 08/05/2013 09:00 PM, Nick Foster wrote:
>> A couple of seconds seems pretty fast, however. Make sure you're
>> resampling the audio to a rate which is actually supported by your
>> soundcard.
>> --n
> The two-clock problem tends to manifest as the occasional "click" or
> occasional 'O'.
> But if the rates between USRP source, and audio sink are significantly
> mis-matched, you end up with overruns very quickly, since buffers will
>   start to fill up to exhaustion, since the sink isn't taking samples as
> fast as they're being produced.
> There's no "magic" rate-adaptation in Gnu Radio.  If you have a filter
> block that is decimating down to, let's say, 50kHz, and then feed it into
>   an audio sink that's expecting data at 48kHz, things will get stuffed
> pretty quickly.  Just because a (hardware) sink is expect data at
>   some rate, doesn't mean that Gnu Radio automatically "tweaks" the flow
> graph to deliver data at that rate.  Gnu Radio is a streaming
>   architecture, it doesn't actually inherently "know" about sample
> rates, so you have to take care of decimating/interpolating data streams
>   so that things "match".

Ahhhh, now I see. I am getting frequent 'O' and audio clicks and pops. I
had played with the various rates till I got the final audio decimation
very close to an integer value but not quite. The integer value used was
a little lower than needed. I adjusted things some more and got a set of
rates that resulted in an integer decimation for the audio lp filter and
that fixed the problem.

The link to the previous discussion was interesting.

thanks, guys

reply via email to

[Prev in Thread] Current Thread [Next in Thread]