first pass at streaming version, works oK from stroed file

git-svn-id: https://svn.code.sf.net/p/freetel/code@2433 01035d8c-6547-0410-b346-abe4f91aad63

diff --git a/codec2-dev/octave/fsk_horus_stream.m b/codec2-dev/octave/fsk_horus_stream.m
new file mode 100644 (file)
index 0000000..72c9d56
--- /dev/null
+++ b/codec2-dev/octave/fsk_horus_stream.m
@@ -0,0 +1,79 @@
+#!/usr/bin/octave -qf
+
+% fsk_horus_stream.m
+% David Rowe 13 Oct 2015
+%
+% Experimental near space balloon FSK demodulator, takes 8kHz 16 bit samples from 
+% stdin, output txt string on stdout
+%
+% usage:
+%  $ chmod 777 fsk_horus_stream.m
+%  $ rec -t raw -r 8000 -s -2 - | ./fsk_horus_stream.m
+
+fsk_horus;  % include library (make sure calls to functions at bottom are commented out)
+
+more off;
+states = fsk_horus_init();
+N = states.N;
+Rs = states.Rs;
+nsym = states.nsym;
+nin = states.nin;
+nfield = states.nfield;
+npad = states.npad;
+uw = states.uw;
+
+rx = [];
+rx_bits_buf = [];
+
+[s,c] = fread(stdin, N, "short");
+
+while c
+
+  rx = [rx s'];
+ 
+  % demodulate to bit stream
+
+  while length(rx) > nin
+    [rx_bits states] = fsk_horus_demod(states, rx(1:nin)');
+    rx_bits_buf = [rx_bits_buf rx_bits];
+    rx = rx(nin+1:length(rx));
+    nin = states.nin;
+    %printf("nin: %d length(rx): %d length(rx_bits_buf): %d \n", nin, length(rx), length(rx_bits_buf));
+  endwhile
+  % printf("nin: %d length(rx): %d length(rx_bits_buf): %d \n", nin, length(rx), length(rx_bits_buf));
+
+  % look for complete Horus frame, delimited by 2 unique words
+
+  bit = 1;
+  nbits = length(rx_bits_buf);
+  uw_loc1 = find_uw(states, bit, rx_bits_buf);
+
+  if uw_loc1 != -1
+    uw_loc2 = find_uw(states, uw_loc1+length(uw), rx_bits_buf);
+
+    if uw_loc2 != -1
+
+      % Now we can extract ascii chars from the frame
+
+      str = [];
+      st = uw_loc1 + length(states.uw);  % first bit of first char
+      for i=st:nfield+npad:uw_loc2
+        field = rx_bits_buf(i:i+nfield-1);
+        ch_dec = field * (2.^(0:nfield-1))';
+        % filter out unlikely characters that bit errors may introduce, and ignore \n
+        if (ch_dec > 31) && (ch_dec < 91)
+          str = [str char(ch_dec)];
+        else 
+          str = [str char(32)]; % space is "not sure"
+        end
+      end
+      printf("%s\n", str);
+
+      % throw out used bits in buffer
+
+      rx_bits_buf =  rx_bits_buf(uw_loc2-1:length(rx_bits_buf));
+    end
+  end
+  [s,c] = fread(stdin, N, "short");
+
+endwhile