Beginner Question. Continuous 0 prints and 0au prints

[ashok shankar das]

Dear All,
Firstly Thanks for a good SDR with intuitive Frontend.

for last 4 weeks I am playing with Fedora-19, GNU-Radio-3.7.1, RTL-SDR(git), GQRX( git).

every thing is fine until i play FM-Mono broadcast. As I mentioned I am a beginner, When ever I see a new type of spectrum I try to listen.
So by wild guess if change the demod to am / narrowFM then Generaly i see a 0au continuously printed on the terminal. during that time the sound quality
deteriorate too much.

another fact is If I start gqrx and do nothing then a 0 is printed continuously. this stops after i press the start button.

my questions:

1) can any one show/point me to what these '0' and '0au' means.?
2) how to avoid them?
3) is there any web-page where i can see different modulation fft in image format so that i can use proper demod?

thanks in advance.

Ashok.
(Alias bluehole,swldas)

[Alexandru Csete]

On Mon, Sep 23, 2013 at 5:50 AM, ashok shankar das
<ashok...@gmail.com> wrote:
> Dear All,
> Firstly Thanks for a good SDR with intuitive Frontend.
>
> for last 4 weeks I am playing with Fedora-19, GNU-Radio-3.7.1, RTL-SDR(git),
> GQRX( git).
>
> every thing is fine until i play FM-Mono broadcast. As I mentioned I am a
> beginner, When ever I see a new type of spectrum I try to listen.
> So by wild guess if change the demod to am / narrowFM then Generaly i see a
> 0au continuously printed on the terminal. during that time the sound quality
> deteriorate too much.
>
> another fact is If I start gqrx and do nothing then a 0 is printed
> continuously. this stops after i press the start button.
>
> my questions:
>
> 1) can any one show/point me to what these '0' and '0au' means.?
> 2) how to avoid them?

Hi Ashok,

The initial 'O' are a quirk of the driver. As soon as it is loaded it
starts reading samples from the device. However, gqrx will not fetch
the samples before you actually start DSP and the therefore the buffer
in the driver will overflow. It's really harmless as long as it only
comes while gqrx DSP is off.

The 'aU' and broken audio on the other hand means audio underrun and
could indicate that CPU load is too high when you switch to that mode.
There is not much to do about it except optimize code and use faster
cpu. You can try to change the sample rate of the dongle, maybe a
lower rate will be better.

Alex

[Alexandru Csete]

You can also try the following to reduce CPU load:
- Reduce FFT rate and FFT size
- Select "wide" filter
- Set AGC to OFF (okay in FM but you will need it back on in AM and SSB).

Alex

[Ashok Shankar Das]

Hi Alex,

Thank you very much for your prompt reply. and Also thanks a lot for the GQRX project.

>There is not much to do about it except optimize code and use faster cpu.

Well I think I can help if you can tell me which file/code block to look into for optimization. Or you mean the whole code need to be optimize?

Ashok.

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Thanks
Ashok.
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