From 230f717a30b1f9a6e2f04bf1b8dc363d793cc86c Mon Sep 17 00:00:00 2001
From: "Matthias P. Braendli" <matthias.braendli@mpb.li>
Date: Mon, 3 Oct 2022 21:06:48 +0200
Subject: Try to decode ODR-DabMux watermark

---
 src/watermarkdecoder.cpp | 114 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 114 insertions(+)
 create mode 100644 src/watermarkdecoder.cpp

(limited to 'src/watermarkdecoder.cpp')

diff --git a/src/watermarkdecoder.cpp b/src/watermarkdecoder.cpp
new file mode 100644
index 0000000..33eb960
--- /dev/null
+++ b/src/watermarkdecoder.cpp
@@ -0,0 +1,114 @@
+/*
+    Copyright (C) 2014 CSP Innovazione nelle ICT s.c.a r.l. (http://www.csp.it/)
+    Copyright (C) 2020 Matthias P. Braendli (http://www.opendigitalradio.org)
+    Copyright (C) 2015 Data Path
+
+    This program 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 of the License, or
+    (at your option) any later version.
+
+    This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
+
+    Authors:
+         Sergio Sagliocco <sergio.sagliocco@csp.it>
+         Matthias P. Braendli <matthias@mpb.li>
+                   / |  |-  ')|)  |-|_ _ (|,_   .|  _  ,_ \
+         Data Path \(|(||_(|/_| (||_||(a)_||||(|||.(_()|||/
+
+*/
+
+#include <vector>
+#include <sstream>
+#include "watermarkdecoder.hpp"
+
+static std::string calc_watermark(const std::vector<bool>& bits)
+{
+    // First try to find the 0x55 0x55 sync in the waternark data
+    size_t bit_ix;
+    int alternance_count = 0;
+    bool last_bit = 1;
+    for (bit_ix = 0; bit_ix < bits.size(); bit_ix++) {
+        if (alternance_count == 16) {
+            break;
+        }
+        else {
+            if (last_bit != bits[bit_ix]) {
+                last_bit = bits[bit_ix];
+                alternance_count++;
+            }
+            else {
+                alternance_count = 0;
+                last_bit = 1;
+            }
+        }
+    }
+
+    if (bit_ix < bits.size()) {
+        fprintf(stderr, "Found SYNC at offset %zu out of %zu\n",
+                bit_ix - alternance_count, bits.size());
+
+        std::stringstream watermark_ss;
+
+        uint8_t b = 0;
+        size_t i = 0;
+        while (bit_ix < bits.size()) {
+
+            b |= bits[bit_ix] << (7 - i);
+
+            if (i == 7) {
+                watermark_ss << (char)b;
+
+                b = 0;
+                i = 0;
+            }
+            else {
+                i++;
+            }
+
+            bit_ix += 2;
+        }
+
+        return watermark_ss.str();
+    }
+    else {
+        return "";
+    }
+}
+
+WatermarkDecoder::WatermarkDecoder() {}
+
+void WatermarkDecoder::push_fig0_1_bit(bool bit)
+{
+    // The order of FIG0_1 subchannels represents the bits
+    m_fig0_1_bits.push_back(bit);
+}
+
+void WatermarkDecoder::push_confind_bit(bool confind)
+{
+    // The ConfInd of FIG 0/10 contains the CRC-DABMUX and ODR-DabMux watermark
+    m_confind_bits.push_back(confind);
+}
+
+std::string WatermarkDecoder::calculate_watermark()
+{
+    std::string w_old = calc_watermark(m_confind_bits);
+    std::string w_new = calc_watermark(m_fig0_1_bits);
+    if (not w_new.empty()) {
+        return w_new;
+    }
+    else if (not w_old.empty()) {
+        return w_old + " (old watermark)";
+    }
+    else {
+        return "(NOT FOUND)";
+    }
+}
+
+
-- 
cgit v1.2.3