Re: USRP N210 growing latencies

Hi Marcus,

How to increase the size on the buffer at the output of the USRP source ?

Improve my flowgraph : maybe possible but I already did some improvment
? I cascade 3 Xlating FIR filter with growing decimation (5, 10, 25) and
already try to limitate the number of taps. I have to work with a
12,5Msps source, make my duties at 10ksps and then output to the sink at
200Ksps (the lowest value of the USRP). I tried XLating FFT filter but
it was worst.

Thanks for your help,

Regards,

Fabien, F4CTZ.

Le 31/10/2021 à 13:03, Marcus Müller a écrit :
> Hi Fabien,
>
> risking sounding a bit cliché: Well, you need to fix your bug. The underflow should not be
> happening!
>
> An easy solution, if this is just a manner of occasionally insufficient, but
> on-the-medium-term more-than-sufficient processing speed, a larger buffer between the USRP
> source and the next block, maybe?
>
> Maybe we can otherwise help you improve the performance of your application :) Just let us
> know!
>
> Best regards,
> Marcus
>
> On 30.10.21 00:20, Fabien PELLET wrote:
>> Hi,
>>
>> Thanks for the answer.
>>
>> At the moment, it seems that catching the underflow message and then lock/unlock the
>> flowgraph permits to reset the buffers and is enough for my application to get reasonnable
>> and not growing forever latencies. I don't if someone know a better way like a C++ method
>> that could do that more "elegantly".
>>
>> If I need more predictible latencies in the futur, indeed, I will try to use tags as you
>> suggest.
>>
>> Regards,
>>
>> Fabien, F4CTZ.
>>
>> Le 27/10/2021 à 17:02, Sylvain Munaut a écrit :
>>> Hi,
>>>
>>>
>>>> OK I understand that. But is there any solution which permits to reset that growing
>>>> propagation delay ? How to reset the flowgraph buffers without killing the application
>>>> and restart it ? Is there any method that permits to purge and resync buffers of the
>>>> flowgraph ?
>>> The USRP supports timestamps for RX and TX.
>>> So you get tags for when data was received / is supposed to be transmitted.
>>> Using a custom block to modify the RX tags into TX tags ( to change
>>> the RX timestamps to TX timestamps a bit into the future ), you should
>>> be able to achieve a constant controlled latency.
>>>
>>> Cheers,
>>>
>>>      Sylvain