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

[Martin Braun]

On 07/21/2014 02:04 PM, hutiantian wrote:
> Hi Martin,
> What's the TSB tags? Does the tags have the different types? I think the
> tags just a pair of key-value.

http://gnuradio.org/doc/doxygen/page_tagged_stream_blocks.html

M
> 
> Thanks
> Tiankun
> 
> 于 2014年07月21日 17:54, Martin Braun 写道:
>> 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
>>>>>>
>>>>>>
>>>>>>
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>>>>>
>>>>>
>>>>>
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