Hi Marcus, Brian,
Regarding your question about the device type, I'm using X300 with 2
twinrx under uhd 4.5.
I added some correlation + interpolation to get the accurate delay.
Here's the results :
* with rx_rate0 = 2 *rx_rate1 I get around 11.68 samples in delay, as
per below, whatever rx_rate0 in [390625.0*8, 390625.0*4, 390625.0*2]
delay_f = -11.680166, delay_f/rx_rates[0] = -3.73765e-06,
delay_i = -12, phi = 0.6401
* with rx_rate0 = 4 *rx_rate1 I get around 17.52 samples in delay, as
per below, whatever rx_rate0 in [390625.0*8, 390625.0*4]
delay_f = -17.52644, delay_f/rx_rates[0] = -5.6084e-06,
delay_i = -18, phi = -0.3705
As this delay seems consistent and depends only on the rate ratio, I
suspect, as you suggested, some difference in down-sampling stages
introduce a delay. I tried to see if this delay is some
multiple/congruence of the master clock but could not find any.
Also, with that script I get this error :
[WARNING] [RFNOC::GRAPH] One or more blocks timed out during flush!
I run into this issue at least 50% of the time. And then one of the
buffers, sometimes both buffers, are empty. Still trying to figure out
why...
Thanks anyway, as I make substantial progress with you ;-)
Chris
Christophe Grimault
NovaGrid SAS
Les Jardins de la Teillais
3, allée de la grande égalonne
35740 Pacé, France
Tel : (33)2 23 41 37 97
Mob: (33)6 82 22 46 93
www.novagrid.com
Le 16/12/2024 à 20:26, Marcus D. Leech a écrit :
On 16/12/2024 14:24, Brian Padalino wrote:
My guess is that you're going through another Halfband FIR filter
somewhere, so there is group delay that isn't being accounted for in
the digital filters.
What is the lag (in samples) of the lower rate sampled signal?
Brian
That was my other thought, assuming that the streams really are
starting at the same time--different group delay
due to the different sample rates.
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