Before myths about tagged stream blocks start perpetuating the webs: TPP_DONT on a tagged stream blocks does the same as on any other type of block; however, TSB tags still get through.
A closer inspection of packet_headergenerator_bb (either by reading the source code or the manual page (http://gnuradio.org/doc/doxygen/classgr_1_1digital_1_1packet__headergenerator__bb.html#details) reveals that the actual processing is done in a separate kernel, the header formatter object, which is user-defined. See packet_header_default for an example. M On 07/20/2014 04:54 PM, Marcus Müller wrote: > Hi Tiankun, > > On 20.07.2014 15:50, hutiantian wrote: >> Hi Marcus, >> My tx_ofdm.py is gen by tx_ofdm.grc, there are a >> 'packet_headergenerator_bb' module in it. This module use >> 'set_tag_propagation_policy(TPP_DONT)' to handle tags by itself. > Ah ok! >> I didn't find any code has touch tags in this module, but when I >> connect it to Tag Debug module, I can find the tags output. > This is indeed strange. However, packet_headergenerator_bb is a subclass > of tagged_stream_block [1]. > >> In my opinion, if one module use >> 'set_tag_propagation_policy(TPP_DONT)', and it does not handle it, >> tags will not pass down. > That's generally correct, but there's the tagged stream block exception: > [1], "A note on tag propagation" tells us that one most of the time > would use TPP_DONT to handle all non-length tags, whilst length tags are > always passed forward. > > Hope that helped! > > Greetings, > Marcus > > > [1] http://gnuradio.org/doc/doxygen/page_tagged_stream_blocks.html >> >> Thanks >> Tiankun >> >> 于 2014年07月20日 21:15, Marcus Müller 写道: >>> Hi Tiankun, >>> >>> what's your GNU Radio version [1]? Where did you find that tx_ofdm.py? >>> There is no tx_ofdm.py in my GNU Radio source tree (in none of v3.7.4, >>> v3.6.5 or v3.4.2). There is a tx_ofdm.grc, which can be used to generate >>> a tx_ofdm.py, but that does not (and shouldn't) contain a >>> "set_tag_propagation_policy" line. >>> >>> Greetings, >>> Marcus >>> >>> [1] you can find out by running "gnuradio-config-info -v" >>> On 20.07.2014 14:54, Tiankun Hu wrote: >>>> Hi Experts, >>>> I was reading tx_ofdm.py. I found this module use >>>> 'set_tag_propagation_policy(TPP_DONT)' to handle tags by itself, but I >>>> cann't find the code that used to handle tag in this module. >>>> I knew this module will call 'packet_header_ofdm.header_formatter()' >>>> and >>>> 'packet_header_default.header_formatter()', but I also cann't find the >>>> handle tag code in these functions. >>>> Anyone can help me figure out where does this module process tags? >>>> >>>> Thanks >>>> Tiankun >>>> >>>> >>>> >>>> _______________________________________________ >>>> Discuss-gnuradio mailing list >>>> Discuss-gnuradio@gnu.org >>>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >>> >>> >>> >>> _______________________________________________ >>> Discuss-gnuradio mailing list >>> Discuss-gnuradio@gnu.org >>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >>> >> > > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
