Re: [Discuss-gnuradio] Selective tag drop/strip/block

[Steven Knudsen]

Hi Marcus,

Thanks for the answer to my question. In effective, you have told me that I have likely examined all the “stock” avenues for my issue. 

Indeed, I know about the set_tag_propagation_policy from the development of my own blocks. 

What I was wondering is if there was an existing block that might selectively strip tags, and it looks like I have to (had to, almost done) write my own.

As originally mentioned, I created a single source for PDUs that contained tag info in the meta-data that I needed to feed to later blocks, both my own custom blocks and stock GR blocks. The stock blocks passed the tags from my PDU source, but this was not what I needed. 

I hate to modify an existing block for many reasons (sound, I think), so it seems better to make a new utility block.

BTW, I have a few blocks that I am lobbying my employer to allow to be released into the wild; fingers crossed.

Thanks, again!

Steven Knudsen, Ph.D., P.Eng.

www. techconficio.ca

www.linkedin.com/in/knudstevenknudsen

All the wires are cut, my friends
Live beyond the severed ends.  Louis MacNeice

Hi Steven,

what you're witnessing is the automatic tag propagation that's the default behaviour for GNU Radio blocks.

In your case, default isn't the right behaviour, as it seems!

Luckily, that's pretty easy to change: gr::block::set_tag_propagation_policy() [1]. The default value is TPP_ALL_TO_ALL (I think we have that documented somewhere, but I can't find it, which is the approximate equivalent of undocumented). Call

set_tag_propagation_policy(TPP_DONT);

in your block's constructor, and you should be fine; however, you'll have to manually add input stream tags to your output stream if you need to keep them.

Best regards,

Marcus

[1] http://gnuradio.org/doc/doxygen/classgr_1_1block.html#a476e218927e426ac88c26431cbf086cd