Maybe it could be a track to follow also... I read it very quickly.
I go down to 1e-9 and there is no influence on the attack behaviour.
I try difference sampling rate (200e3 and 1e6 for output on a USRP) and
it influences decay and attack as expected.
I come back to AGC instead of AGC2 and the rate value has an influence
on both attack and decay behaviour as expected.
Hope this will help.
If I would like to play on the code of AGC2, how can I recompile only
this module and not all gnuradio ?
Le 09/12/2021 à 14:52, Jeff Long a écrit :
Maybe "tmp" should be compared to 0, not to gain. It does look
suspicious. Not sure what algorithm the author had in mind.
On Thu, Dec 9, 2021 at 8:41 AM Fabien PELLET <fpellet.f4...@free.fr>
wrote:
Maybe I'm wrong but at line 141, it should be a division and not a
difference ??? I'm telling that because in line 143, the result
"tmp" is compared to the gain. There is a unit problem here I
think : amplitude (result of the difference) can't be compared to
a gain which do not have unit by definition....
I will try wider value for attack.
Le 09/12/2021 à 13:23, Jeff Long a écrit :
The change in gain is also proportional to the difference between
the reference level and the signal level. So it probably is
having some influence but it reacts more quickly. Try a smaller
value for attack. Take a look at the source here
https://github.com/gnuradio/gnuradio/blob/35a242f1cd4b724be0c4708d8690f82c804aafd8/gr-analog/include/gnuradio/analog/agc2.h#L64
for more info. It may just not be a great algorithm, or may not
work for the rates and changes in signal you have.
On Thu, Dec 9, 2021 at 7:07 AM Fabien PELLET
<fpellet.f4...@free.fr> wrote:
Thanks for the explanation.
Do you have any idea on why the attack as no influence ?
Le 09/12/2021 à 12:58, Jeff Long a écrit :
Attack and decay are unitless per-sample multipliers, so
1.0e-2 gives you a time "on the order of" 100 samples. It's
really an exponential attack and decay, but that gives you
an idea. So, your observation is correct - a smaller value
gives you a longer attack/decay.
On Thu, Dec 9, 2021 at 4:33 AM Fabien PELLET
<fpellet.f4...@free.fr> wrote:
Hello,
I'm trying to work with the module AGC2 but I have some
trouble using it.
First problem is : what is the unit of the parameters
attack and decay ?
I thought initially that it was in second but after some
test it is
clearly not in that unit. Indeed, if I increase the
value of the decay
for example, the time of the increase of the gain at the
end of a signal
will go down where it should go up.
Second problem (maybe in relation with the first) : the
attack value
have absolutly no influence.... From 10-6 to 10-2, I
can't see any
changes on the output signal.
Does someone have any explanation ?
Best regards,
Fabien, F4CTZ.
