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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"
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;
}
}
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