Re: [Discuss-gnuradio] simple mod-demod combinations doesn't work

[MarkO]

Dear Marcus,
thanks for your response.

Marcus Müller-3 wrote
> That sounds like a unrelated thing; aU's typically happen when you have
> two clocks in your system, for example, one SDR device's sampling clock
> and a soundcard sampling clock, as those never align perfectly, and one
> can drift away from each other, or if you actually made a mistake
> somewhere and the rate conversions between signal source hardware and
> signal sink hardware don't actually result in the sink's clock rate.
> You're not using a throttle block together with an audio sink, are you?
> 
> The console output will tell you that using throttle + audio sink =
> evil. Throttle must never be used with hardware that has its own sample
> clock.

Yes, I also tested the audio stream with a throttle block and I understand
the problem with [throttle] + hardware, but as you said:

Marcus Müller-3 wrote
> GNU Radio's job is to process samples as fast as it can; it
> doesn't care, or even know, about how fast these samples should occur
> related to "real world time".

That can be a problem in some cases, but probably only for me because I
don't understand something essential..

The only blocking element is the [audio sink] in "blocking mode" (of
course).
If i start an audio flow graph without [throttle] and increase some additive
noise or change the volume with a multiplier in the stream the audible
signal gets effected way too slow (action-to-effect-time approximately 10 s
or more). If I use a [throttle] after the [wav file source] i can effect the
stream directly - maybe i can call it "in real time", but then sometimes aU
occurs.

The issue remains also if i use real hardware (redpitaya with osmocom
blocks) an resampler blocks in the stream.

So is the solution for such problems a tagged stream with control through
tags or the usage of PDUs?

Regards,
Markus





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