89 lines
2.4 KiB
C++
89 lines
2.4 KiB
C++
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//
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// Created by Grishka on 24/03/2019.
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//
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#include "../logging.h"
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#include "VideoFEC.h"
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#include <cstring>
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#include <cstdint>
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#include <algorithm>
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using namespace tgvoip;
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using namespace tgvoip::video;
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Buffer ParityFEC::Encode(const std::vector<Buffer>& packets)
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{
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std::size_t maxSize = 0;
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for (const Buffer& pkt : packets)
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{
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maxSize = std::max(maxSize, pkt.Length());
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}
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Buffer result(maxSize + 2); // add 2 bytes for length
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std::uint8_t* resultPtr = *result;
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std::memset(resultPtr, 0, result.Length());
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for (const Buffer& pkt : packets)
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{
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for (std::size_t i = 0; i < pkt.Length(); ++i)
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{
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resultPtr[i] ^= pkt[i];
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}
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std::uint16_t len = static_cast<std::uint16_t>(pkt.Length());
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resultPtr[maxSize + 0] ^= static_cast<std::uint8_t>(len >> 0);
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resultPtr[maxSize + 1] ^= static_cast<std::uint8_t>(len >> 8);
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}
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return result;
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}
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Buffer ParityFEC::Decode(const std::vector<Buffer>& dataPackets, const Buffer& fecPacket)
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{
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std::size_t maxSize = 0;
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for (const Buffer& pkt : dataPackets)
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{
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maxSize = std::max(maxSize, pkt.Length());
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}
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if (fecPacket.Length() < maxSize + 2)
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{
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LOGE("ParityFEC: FEC packet too small (%u, expected >=%u)", static_cast<unsigned int>(fecPacket.Length()), static_cast<unsigned int>(maxSize + 2));
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return Buffer();
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}
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Buffer result = Buffer::CopyOf(fecPacket);
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std::uint8_t* resultPtr = *result;
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unsigned int emptyCount = 0;
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for (const Buffer& pkt : dataPackets)
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{
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if (pkt.Length() == 0)
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{
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++emptyCount;
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continue;
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}
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for (std::size_t i = 0; i < pkt.Length(); ++i)
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{
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resultPtr[i] ^= pkt[i];
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}
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std::uint16_t len = static_cast<std::uint16_t>(pkt.Length());
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resultPtr[maxSize + 0] ^= static_cast<std::uint8_t>(len >> 0);
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resultPtr[maxSize + 1] ^= static_cast<std::uint8_t>(len >> 8);
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}
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if (emptyCount != 1)
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{
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LOGE("ParityFEC: %u packets lost", emptyCount);
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return Buffer();
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}
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std::uint16_t len = static_cast<std::uint16_t>(resultPtr[maxSize + 0] << 0) |
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static_cast<std::uint16_t>(resultPtr[maxSize + 1] << 8);
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if (len > maxSize)
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{
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LOGE("ParityFEC: incorrect length %u", len);
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return Buffer();
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}
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LOGV("ParityFEC decoded packet size %u", len);
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result.Resize(len);
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return result;
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}
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