Re: [Discuss-gnuradio] Fractional resampler eats stream tags on changes on the "ratio" input

[Tom Rondeau]

On Wed, Sep 23, 2015 at 4:06 PM, Piotr Krysik <address@hidden> wrote:

Hi all,

Fractional resampler has additional "rate" signal input for supplying
resampling ratio for each input signal sample.
Changes of the signal on the "ratio" input might result in loss of tags
that are close in time to these changes.

I observed the problem when I was implementing frequency offset
corrector (attached flowgraph screenshot).
Short description what is going on there:
-when message comes to ppm_in port of the block "Controlled const
source" changes value of constant at the output,
-when Controlled rotator observe this change on its input, it emits
stream tag,
-for changes of about +/-50ppm (and above) on the 'ratio' input of the
Fractional Resampler, tags coming from the Controlled rotator are not
going through.

Just by looking at the Fractional Resampler implementation
(https://github.com/gnuradio/gnuradio/blob/master/gr-filter/lib/fractional_resampler_cc_impl.cc#L104)
I'm not able to locate source of the problem.

I can implement minimal working example if needed.

Best Regards,
Piotr Krysik

Piotr,

Looking at the block, I was hoping it was as easy as putting a set_relative_rate call in the set_resamp_rate to adjust how the tags are being propagated. But it's not that simple. See Issue #846 (http://gnuradio.org/redmine/issues/846) for details on the problem.

Tom