Dear Veljko Pejovic, My thought is,
when you detect a certain beginning of transmission, get the offset of it. And add tag whose value is the offset. At the end of the chain, sink block has two ports, and one receives the original one, and the other receives the processed one. And compare original[offset:] with processed[:] Stream Tags: https://gnuradio.org/doc/doxygen/page_stream_tags.html Regards, Jeon. 2015-10-26 23:26 GMT+09:00 Veljko Pejovic <veljkovel...@gmail.com>: > Hi, > > I would like to process samples from a USRP (let's use FM > demodulation, for example) and then identify which of the original > samples correspond to a particular result at the end of the chain > (say, a beginning of a stereo transmission, a beginning of a song, > etc.). > > The problem is, in the process of filtering, demodulation and > evaluation I lose the original samples. If, at the point of detection > I go back and fetch samples from USRP, those won't be the exact > samples corresponding to the generated result. Moreover, since the > delay the original samples take to go through the processing chain is > varying and unpredictable (I learnt that in my last experiment, and > thank you Macus for explaining this), I can't just build a parallel > chain that will merely delay the samples, and then fetch those delayed > samples. > > So, what is the solution? One idea I have is to extend each block in > the processing chain with another input/output port and carry along > the original samples. Then, in the end, when I evaluate the result, I > can just take the piggybacked samples, and be sure that those are the > ones that generated the result. However, this means I have to modify > each block in the chain. Is there a more elegant solution to the > problem? > > Thanks, > > > Veljko > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >
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