From IQ to pi/4 DQPSK I need to decode $\frac\pi4$-DQPSK packets from an SDR, preferably in C#.

I have the SDR receiver part done. Now I'm trying to learn how to take the IQ stream and get the packet info from it. 

I've gone through the math, but don't understand the notation. I've tried GNU Radio, but can't get blocks added on a windows machine. I can't find a library that I can get working. I know this is rather opened ended question, but can anyone steer me in a direction to do this? I've been programming for going on 42 years now, but this is my first foray into DSP, and at my age it doesn't come easy anymore. 

If it helps any, I do know a lot about the packets I'm trying to grab. They are transmitted in pi/4 DQPSK at 16kbps or 32kbps (there are two packet types), with a preamble of f337eeb637660672. The packet format is known to me, and is not encrypted.  This is for a project that will be released for free, which combined with my being retired hampers any ability to pay for professional help.
The OP stated he was interested in $\pi/4$-DQPSK (not QPSK), so phase synchronization is presumably not an issue for him.

As far as the actual implementation is concerned, you'll save yourself some time if you become familiar with the bottom of pages 29 (symbol mapping) and 37 (differential detection) in this student paper. Ignore all the old TI DSP-chip specific information and the information on pulse-shaping, which is already built into GNU Radio (if the OP is using that). There is also a reasonable description of a simple timing recovery algorithm. It is serviceable in some scenarios, but not others.