X-Git-Url: https://git.gag.com/?a=blobdiff_plain;f=gr-atsc%2Fsrc%2Flib%2Fatsci_reed_solomon.cc;fp=gr-atsc%2Fsrc%2Flib%2Fatsci_reed_solomon.cc;h=e20e76d71363b1efa57e564eecdf9667834c0fa9;hb=8a9ddbb0675f9bfcc6e03b457fba6c79474a3693;hp=0000000000000000000000000000000000000000;hpb=82d471b9b4a8b389b5da44b19c69c36420828382;p=debian%2Fgnuradio

diff --git a/gr-atsc/src/lib/atsci_reed_solomon.cc b/gr-atsc/src/lib/atsci_reed_solomon.cc
new file mode 100644
index 00000000..e20e76d7
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+++ b/gr-atsc/src/lib/atsci_reed_solomon.cc
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+/* -*- c++ -*- */
+/*
+ * Copyright 2002 Free Software Foundation, Inc.
+ * 
+ * This file is part of GNU Radio
+ * 
+ * GNU Radio is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3, or (at your option)
+ * any later version.
+ * 
+ * GNU Radio is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with GNU Radio; see the file COPYING.  If not, write to
+ * the Free Software Foundation, Inc., 51 Franklin Street,
+ * Boston, MA 02110-1301, USA.
+ */
+
+#include <atsci_reed_solomon.h>
+#include <assert.h>
+#include <string.h>
+
+extern "C" {
+#include "rs.h"
+}
+
+static const int rs_init_symsize =     8;
+static const int rs_init_gfpoly  = 0x11d;
+static const int rs_init_fcr     =     0;	// first consecutive root
+static const int rs_init_prim    =     1;	// primitive is 1 (alpha)
+static const int rs_init_nroots  =    20;
+
+static const int N = (1 << rs_init_symsize) - 1;	// 255
+static const int K = N - rs_init_nroots;		// 235
+
+static const int amount_of_pad	 = N - ATSC_MPEG_RS_ENCODED_LENGTH;	  // 48
+
+atsci_reed_solomon::atsci_reed_solomon ()
+{
+  d_rs = init_rs_char (rs_init_symsize, rs_init_gfpoly,
+		       rs_init_fcr, rs_init_prim, rs_init_nroots);
+
+  assert (d_rs != 0);
+}
+
+atsci_reed_solomon::~atsci_reed_solomon ()
+{
+  if (d_rs)
+    free_rs_char (d_rs);
+  d_rs = 0;
+}
+
+void
+atsci_reed_solomon::encode (atsc_mpeg_packet_rs_encoded &out, const atsc_mpeg_packet_no_sync &in)
+{
+  unsigned char tmp[K];
+
+  assert ((int)(amount_of_pad + sizeof (in.data)) == K);
+  
+  // add missing prefix zero padding to message
+  memset (tmp, 0, amount_of_pad);
+  memcpy (&tmp[amount_of_pad], in.data, sizeof (in.data));
+
+  // copy message portion to output packet
+  memcpy (out.data, in.data, sizeof (in.data));
+
+  // now compute parity bytes and add them to tail end of output packet
+  encode_rs_char (d_rs, tmp, &out.data[sizeof (in.data)]);
+}
+
+int
+atsci_reed_solomon::decode (atsc_mpeg_packet_no_sync &out, const atsc_mpeg_packet_rs_encoded &in)
+{
+  unsigned char tmp[N];
+  int		ncorrections;
+
+  assert ((int)(amount_of_pad + sizeof (in.data)) == N);
+  
+  // add missing prefix zero padding to message
+  memset (tmp, 0, amount_of_pad);
+  memcpy (&tmp[amount_of_pad], in.data, sizeof (in.data));
+
+  // correct message... 
+  ncorrections = decode_rs_char (d_rs, tmp, 0, 0);
+  
+  // copy corrected message to output, skipping prefix zero padding
+  memcpy (out.data, &tmp[amount_of_pad], sizeof (out.data));
+
+  return ncorrections;
+}