doc/notes.txt : Added notes.

doc/notes.txt

        Enable/Disable selected events.
         
      
-    
+=============================================================================
+
+                                  
+                                      
+                             a                   b
+    piano --> mic ----> adc --> fbctl --> xform -+-> dac --> spkr --> room --+
+     ^         ^                  ^              |                           |
+     |         |                  |              |                           |
+     |         |                  +--------------+                           |
+     +---------+-------------------------------------------------------------+
+
+fbctl Design:
+
+      
+
+1. Measure the spectrum of the room impulse response.
+   a. Generate a sine sweep, or Max. length sequance, s,  with a non-symetric envelope.
+               
+   b. Playback s and record the result N times
+      using different mic. positions.
+      
+   c. S = STFT(s)
+      R = sum(STFT(r_i) / N
+      
+   d. Align S and R using PHAT.
+   e. RIR = mean(S - R)
+
+
+2. Find the delay, d, which minimizes sum(a-b)
+
+       a ----------> DFT() --\
+                              - --->  
+       b --> z^d --> DFT() --/
+       
+
+=============================================================================
+
+  1. Use spectral flux to generate an impulse signal: f.
+  2. f' = 1-f correlates to the level of time dependency in the signal.
+     Frames with a high time dependency contain more reberberated signal.
+  3. Setup a 2xT NMF problem  Y = HE
+  4. Initialize spectrum 1 as the f weighted avg. of all spectra.
+  5. Initialize spectrum 2 as the f' weighted avg. of all spectra.
+  6. Initialize env. 1 as f
+  7. Initialize env. 2 as f'
+  8. Allow all other variables, other than f', to vary - spectrum 2
+     is the impulse response.  
+
+   alternatively use gradient descent, or alternating LS, rather than NMF
+
+
+=============================================================================
+
+New vector library:
+1. Use type generic pre-proc feature.
+2. Explicit matrix representation.
+3. Use BLAS and LAPACK.
 
 
 =============================================================================