From: drowe67 <drowe67@01035d8c-6547-0410-b346-abe4f91aad63>
Date: Sat, 17 Sep 2016 02:39:56 +0000 (+0000)
Subject: ldpc encoded SSTV frames
X-Git-Url: http://git.whiteaudio.com/gitweb/?a=commitdiff_plain;h=4392410425ebb474081ff7b06659f35fea03fd05;p=freetel-svn-tracking.git

ldpc encoded SSTV frames

git-svn-id: https://svn.code.sf.net/p/freetel/code@2874 01035d8c-6547-0410-b346-abe4f91aad63
---

diff --git a/codec2-dev/octave/ldpc_fsk_lib.m b/codec2-dev/octave/ldpc_fsk_lib.m
index 33035abd..72d93148 100644
--- a/codec2-dev/octave/ldpc_fsk_lib.m
+++ b/codec2-dev/octave/ldpc_fsk_lib.m
@@ -255,17 +255,43 @@ end
 % One application of FSK LDPC work is SSTV.  This function generates a
 % simulated frame for testing
 
-function [bytes rs232_bits] = gen_sstv_frame
+function frame_rs232 = gen_sstv_frame
+  load('H2064_516_sparse.mat');
+  HRA = full(HRA);  
+  mod_order = 2;
+  code_param = ldpc_init(HRA, mod_order);
+
+  % generate payload data bytes and checksum
+
   data = floor(rand(1,256)*256);
+  % data = zeros(1,256);
   checksum = crc16(data);
+  data = [data hex2dec(checksum(3:4)) hex2dec(checksum(1:2))];
+
+  % unpack bytes to bits and LPDC encode
+
+  mask = 2.^(0:7);
+  unpacked_data = [];
+  for b=1:length(data)
+    unpacked_data = [unpacked_data bitand(data(b), mask) > 0];
+  end
+  codeword = ldpc_encode(code_param, unpacked_data);
+
+  % generate unpacked header bits
+
   uw = 'abcd';
-  bytes = [hex2dec('55')*ones(1,16) hex2dec('ab') hex2dec('cd')];
-  bytes = [bytes data hex2dec(checksum(3:4)) hex2dec(checksum(1:2))];
+  header = [hex2dec('55')*ones(1,16) hex2dec('ab') hex2dec('cd')];
+  unpacked_header = [];
+  for b=1:length(header)
+    unpacked_header = [unpacked_header bitand(header(b), mask) > 0];
+  end
+  frame = [unpacked_header codeword 0 0 0 0]; % integer number of bytes
+
+  % insert rs232 framing bits
 
-  mask = 2.^(0:7); rs232_bits = [];
-  for b=1:length(bytes)
-    bits = bitand(bytes(b),mask) > 0;
-    rs232_bits = [rs232_bits 0 bits 1];
+  frame_rs232 = [];
+  for b=1:8:length(frame)
+    frame_rs232 = [frame_rs232 0 frame(b:b+7) 1];
   end
 endfunction
 
diff --git a/codec2-dev/octave/test_ldpc_fsk_lib.m b/codec2-dev/octave/test_ldpc_fsk_lib.m
index c2253a69..43a1348c 100644
--- a/codec2-dev/octave/test_ldpc_fsk_lib.m
+++ b/codec2-dev/octave/test_ldpc_fsk_lib.m
@@ -266,7 +266,7 @@ rand('state',1);
 
 % binary flags to run various demos, e.g. "15" to run 1 .. 8
 
-demo = 7;
+demo = 8;
 
 if demo == 1
   printf("simple_ut....\n");
@@ -320,6 +320,24 @@ if demo == 7
 end
 
 if demo == 8
-   [bytes rs232_bits] = gen_sstv_frame;
-   f = fopen("sstv.bin","wb"); fwrite(f, rs232_bits, "uint8"); fclose(f);
+  frames = 100;
+  EsNodB = 3;
+  EsNo = 10^(EsNodB/10);
+  variance = 1/(2*EsNo);
+
+  frame_rs232 = [];
+  for i=1:frames
+    frame_rs232 = [frame_rs232 gen_sstv_frame];
+  end
+
+  % write hard decn version to disk file, useful for fsk_mod input
+
+  f = fopen("sstv.bin","wb"); fwrite(f, frame_rs232, "char"); fclose(f);
+
+  % soft decision version (with noise)
+
+  s = 1 - 2*frame_rs232;
+  noise = sqrt(variance)*randn(1,length(frame_rs232)); 
+  r = s + noise;
+  f = fopen("sstv_sd.bin","wb"); fwrite(f, r, "float32"); fclose(f);
 end