Re: [Discuss-gnuradio] Throttle block form wav files

[Kevin Reid]

On Sep 3, 2015, at 7:22, Murray Thomson <address@hidden> wrote:

> I'm using a flow graph with no GUI to demodulate a signal. I have a selector 
> block that allows me to select the source of the signal between the audio 
> card and a wav file. I can change the source using an xmlrpc server/client.
> 
> If I don't use a throttle block with the wav file, the flow graph takes all 
> the CPU and the server/client is very slow.
> If I put a throttle, I get audio underruns when using the audio card. Same 
> problem for a constant source.

You can't get audio underruns from an audio _source_, so I assume you have an 
audio _sink_ that you didn't mention in your description that you're using in 
both modes for the output of the demodulator.

It sounds like you have the audio _sink_ set not to block. In its properties, 
enable the “OK to Block” checkbox. Do not use a throttle.

This will allow the audio sink to limit the data rate from the wav source (by 
backpressure). When an audio source is being used, if the source and sink are 
from the same sound card and have the same sample rate requested then they 
should be happy too.

-- 
Kevin Reid                                  <http://switchb.org/kpreid/>