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-rw-r--r--lib/edioutput/Interleaver.cpp122
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diff --git a/lib/edioutput/Interleaver.cpp b/lib/edioutput/Interleaver.cpp
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+/*
+ Copyright (C) 2017
+ Matthias P. Braendli, matthias.braendli@mpb.li
+
+ http://www.opendigitalradio.org
+
+ EDI output,
+ Interleaving of PFT fragments to increase robustness against
+ burst packet loss.
+
+ This is possible because EDI has to assume that fragments may reach
+ the receiver out of order.
+
+ */
+/*
+ This file is part of ODR-DabMux.
+
+ ODR-DabMux 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.
+
+ ODR-DabMux 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 ODR-DabMux. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "Interleaver.h"
+#include <cassert>
+
+namespace edi {
+
+void Interleaver::SetLatency(size_t latency_frames)
+{
+ m_latency = latency_frames;
+}
+
+Interleaver::fragment_vec Interleaver::Interleave(fragment_vec &fragments)
+{
+ m_fragment_count = fragments.size();
+
+ // Create vectors containing Fcount*latency fragments in total
+ // and store them into the deque
+ if (m_buffer.empty()) {
+ m_buffer.emplace_back();
+ }
+
+ auto& last_buffer = m_buffer.back();
+
+ for (auto& fragment : fragments) {
+ const bool last_buffer_is_complete =
+ (last_buffer.size() >= m_fragment_count * m_latency);
+
+ if (last_buffer_is_complete) {
+ m_buffer.emplace_back();
+ last_buffer = m_buffer.back();
+ }
+
+ last_buffer.push_back(std::move(fragment));
+ }
+
+ fragments.clear();
+
+ while ( not m_buffer.empty() and
+ (m_buffer.front().size() >= m_fragment_count * m_latency)) {
+
+ auto& first_buffer = m_buffer.front();
+
+ assert(first_buffer.size() == m_fragment_count * m_latency);
+
+ /* Assume we have 5 fragments per AF frame, and latency of 3.
+ * This will give the following strides:
+ * 0 1 2
+ * +-------+-------+---+
+ * | 0 1 | 2 3 | 4 |
+ * | | +---+ |
+ * | 5 6 | 7 | 8 9 |
+ * | +---+ | |
+ * |10 |11 12 |13 14 |
+ * +---+-------+-------+
+ *
+ * ix will be 0, 5, 10, 1, 6 in the first loop
+ */
+
+ for (size_t i = 0; i < m_fragment_count; i++) {
+ const size_t ix = m_interleave_offset + m_fragment_count * m_stride;
+ m_interleaved_fragments.push_back(first_buffer.at(ix));
+
+ m_stride += 1;
+ if (m_stride >= m_latency) {
+ m_interleave_offset++;
+ m_stride = 0;
+ }
+ }
+
+ if (m_interleave_offset >= m_fragment_count) {
+ m_interleave_offset = 0;
+ m_stride = 0;
+ m_buffer.pop_front();
+ }
+ }
+
+ std::vector<PFTFragment> interleaved_frags;
+
+ const size_t n = std::min(m_fragment_count, m_interleaved_fragments.size());
+ std::move(m_interleaved_fragments.begin(),
+ m_interleaved_fragments.begin() + n,
+ std::back_inserter(interleaved_frags));
+ m_interleaved_fragments.erase(
+ m_interleaved_fragments.begin(),
+ m_interleaved_fragments.begin() + n);
+
+ return interleaved_frags;
+}
+
+}
+
+