Re: [Discuss-gnuradio] ninput_items size problem

Hello Rear,

Thank you for response. I could resolve the partial samples problem. I
give custom taps to Rational_resampler as "[1.0]". This time, it gave
full output without any partial data. However, this causes multiple
images in spectrum due to interpolation. I used a low pass filter after
rational_resampler. This solved filtering issue. I have attached picture
of my FG.

I can send full tagged packets with this configuration. But, this causes
me getting letter "D". After getting couple of letter "D", RX LED of
USRP turns off. RX functionality of USRP crashes. When i searched that
means "Dropped Network Packet". But i cannot understand how my changes
caused that problem.

Do you have any idea?

Regards.

On 12.07.2019 10:52, rear1019 wrote:
> On Wed, 10 Jul 2019 at 19:15:41 +0300, Ramazan Çetin wrote:
>> We made some progress. This short ninput_items size problem results from
>> "rational_resampler". Rational_resampler is used as interpolator by 2. So,
>> lets say, there is a tagged packet on input of rational_resampler with
>> length of 975. We expect that, rational_resampler should put a packet to the
>> output with size of 1950. But, it outputs partially like length of 1024 or
>> 1536 etc. So, next block cannot produce its output. Because it needs entire
>> packet with length of 1950.
>>
>> Can we set min noutput_items for rational_resampler and does this solve the
>> problem? Or, do you know what the problem is about rational_resampler?
> That's not a problem with rational_resampler, that's how GNU Radio
> works. ninput_items and noutput_items depend on various factors and are
> not deterministic. A minimum ninput_items can be forced indirectly by
> using set_min_noutput_items() inside the block which requires a minimum
> ninput_items. I don't know whether calling this function in the upstream
> block (in rational_resampler, as suggested by you) will work.
>
> You do call set_min_noutput_items() in your code, however, the argument
> is too small; increase it to 1950. Note that generally you must take the
> implementation of forecast() into account: You use gr::block as base
> class and you don't overwrite forecast(). The default implementation [1]
> assumes a 1:1 rate of input to output items. With gr::sync_interpolator
> e.g. you must use set_min_noutput_items(minimum ninput_items times
> interpolation factor).
>
> [1] https://github.com/gnuradio/gnuradio/blob/maint-3.7/gnuradio-runtime/lib/block.cc#L115