Re: [Discuss-gnuradio] pdu and stream tagging in 3.6.3

[Nowlan, Sean]

>On Fri, Feb 08, 2013 at 07:14:48PM +0000, Nowlan, Sean wrote:
>> I'm playing around with the new 
>> gr_pdu_to_tagged_stream/gr_tagged_stream_to_pdu
>> blocks. Is there something that can translate between the new tag format and
>> the standard tx_sob (start of burst)/tx_eob (end of burst)/tx_time tags?
>
>Hi Sean,
>
>there's only one type of tags--I'm not sure what you're asking here.

What I meant was that gr_pdu_to_tagged_stream doesn't tag with 
tx_sob/tx_time/tx_eob, and so the format has to be "translated" by a downstream 
block's work(...) function from PDU tags to burst tags.

>> I guess it's possible to write a packet scheduler if you fix a timestamp in 
>> the
>> PMT metadata dictionary? I think this would involve writing a message source
>> block that could attach PMT pairs containing tx_sob/PMT_T and tx_time/tuple
>> (uint64_t secs, double frac_secs). A downstream block could read the 
>> pdu_length
>> tag and put a tx_eob/PMT_T stream tag at the appropriate place. Does this 
>> sound
>> like a reasonable approach?
>
>That sounds exactly like something I discussed with Johnathan recently.
>Not everything you've described is there in GNU Radio, but it sounds
>reasonable.

I think all the elements are there in v3.6.3 to write such a block. But I'm 
confusing myself. In gnuradio-core/src/lib/io, gr_message_burst_source sort of 
implements this functionality (tx_sob & tx_eob, but no tx_time). It seems the 
PDU-to-tagged-stream concept is a parallel solution that adds a "length" tag 
and whatever is in the metadata dictionary, but doesn't use tx_sob/tx_eob tags 
explicitly. Am I reading this correctly?

-sean