Hi everyone and merry Christmas! :)
I want to find the same snippet of I/Q data of a radio station in another I/Q recording of the same station but recorded with another dongle. Of course both with rtl-sdr dongles.
I did this here
http://filebin.net/8nevid3yk3and played around with a python script and numpy math-lib to find this "needle" in the "haystack" and the timeshift. But it didn't work. That's why I am here to ask you how to do that.
First of all, I would like to ask you if you could somehow check if both streams are actually containing the "same" I/Q data. Perhaps you can do that with one other software if you can find it.
What I did was to use the numpy correlate function and added there some lines to have it normalized to have the results between -1 and 1 as explained here
http://en.wikipedia.org/wiki/Cross-correlation#Normalized_cross-correlationBut it couldn't find a needle sequence of 1000 samples that could be refound in the haystack (about 2000000 samples) when the starting of the needle samples were shifted a bit with some new 1000 samples.
I guess that the analogue radio channel on this carrier and thus the I/Q doesn't form the I/Q enough to use each sample on that 2MHz sample rate, but much less in the KHz range. But I am not fully sure if this is true. This is why I am also here to ask about the influences on a cross correlation and how to set it up.
So, any answer is very welcome. I hope it will work out in the end :).