Re: [Discuss-gnuradio] how does Packet Header Generator module handle tags

[Marcus Müller]

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
>>>
>>>
>>>
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>>
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