Allow creation of ATMOS sync on channel 14.atmos

1 files changed, 121 insertions, 0 deletions

diff --git a/src/fsk.cc b/src/fsk.cc
new file mode 100644
index 00000000..4755e560
--- /dev/null
+++ b/src/fsk.cc
@@ -0,0 +1,121 @@
+/*
+    Copyright (C) 2020 Carl Hetherington <cth@carlh.net>
+
+    This file is part of libdcp.
+
+    libdcp 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 2 of the License, or
+    (at your option) any later version.
+
+    libdcp 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 libdcp.  If not, see <http://www.gnu.org/licenses/>.
+
+    In addition, as a special exception, the copyright holders give
+    permission to link the code of portions of this program with the
+    OpenSSL library under certain conditions as described in each
+    individual source file, and distribute linked combinations
+    including the two.
+
+    You must obey the GNU General Public License in all respects
+    for all of the code used other than OpenSSL.  If you modify
+    file(s) with this exception, you may extend this exception to your
+    version of the file(s), but you are not obligated to do so.  If you
+    do not wish to do so, delete this exception statement from your
+    version.  If you delete this exception statement from all source
+    files in the program, then also delete it here.
+*/
+
+
+#include "fsk.h"
+#include <iostream>
+
+
+using std::cout;
+using std::vector;
+using namespace dcp;
+
+
+FSK::FSK ()
+	: _data_position (0)
+	, _sample_position (0)
+	, _last_polarity (false)
+	, _last_bit (false)
+{
+
+}
+
+
+void
+FSK::set_data (vector<bool> data)
+{
+	_data = data;
+	_data_position = _sample_position = 0;
+}
+
+
+int32_t
+FSK::get ()
+{
+	static int const twenty_four_bit = 8388608; // 2^23
+
+	static int const lut[4][2] = {
+		// sample 0
+		{
+			int( 0.03827 * twenty_four_bit), // 0
+			int( 0.07071 * twenty_four_bit), // 1
+		},
+		// sample 1
+		{
+			int( 0.09239 * twenty_four_bit), // 0
+			int( 0.07071 * twenty_four_bit), // 1
+		},
+		// sample 2
+		{
+			int( 0.09239 * twenty_four_bit), // 0
+			int(-0.07071 * twenty_four_bit), // 1
+		},
+		// sample 3
+		{
+			int( 0.03827 * twenty_four_bit), // 0
+			int(-0.07071 * twenty_four_bit), // 1
+		}
+	};
+
+	/* The bit we are working on */
+	bool const bit = _data[_data_position];
+	/* Get the +ve version of the required sample */
+	int sample = lut[_sample_position][bit];
+
+	bool polarity = _last_polarity;
+	if (_sample_position == 0 && _last_bit == false) {
+		/* We're starting a new bit, and the last one was 0 so we need to flip
+		 * the polarity we are using.
+		 */
+		polarity = !polarity;
+	}
+
+	/* Obey the required polarity for this sample */
+	if (polarity == false) {
+		sample = -sample;
+	}
+
+	/* Get ready for next time */
+
+	_last_bit = bit;
+	_last_polarity = polarity;
+
+	++_sample_position;
+	if (_sample_position == 4) {
+		_sample_position = 0;
+		++_data_position;
+	}
+
+	return sample;
+}
+