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ChirpChat demod: FT decoding: try symbol shifts
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@ -54,16 +54,40 @@ void ChirpChatDemodDecoderFT::decodeSymbols(
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return;
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}
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float *lls = new float[mags.size()*nbSymbolBits]; // bits log likelihoods (>0 for 0, <0 for 1)
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std::fill(lls, lls+mags.size()*nbSymbolBits, 0.0);
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// float *lls = new float[mags.size()*nbSymbolBits]; // bits log likelihoods (>0 for 0, <0 for 1)
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// std::fill(lls, lls+mags.size()*nbSymbolBits, 0.0);
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FT8::FT8Params params;
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FT8::FT8::soft_decode_mags(params, mags, nbSymbolBits, lls);
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// FT8::FT8::soft_decode_mags(params, mags, nbSymbolBits, lls);
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int r174[174];
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std::string comments;
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payloadParityStatus = (int) ChirpChatDemodSettings::ParityOK;
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payloadCRCStatus = false;
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std::vector<std::vector<float>> magsp = mags;
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if (FT8::FT8::decode(lls, r174, params, 0, comments) == 0)
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qDebug("ChirpChatDemodDecoderFT::decodeSymbols: try decode with symbol shift 0");
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int res = decodeWithShift(params, magsp, nbSymbolBits, r174, comments);
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if (res == 0)
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{
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std::vector<std::vector<float>> magsn = mags;
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int shiftcount = 0;
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while ((res == 0) && (shiftcount < 7))
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{
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qDebug("ChirpChatDemodDecoderFT::decodeSymbols: try decode with symbol shift %d", shiftcount + 1);
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res = decodeWithShift(params, magsp, nbSymbolBits, r174, comments, 1);
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if (res == 0)
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{
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qDebug("ChirpChatDemodDecoderFT::decodeSymbols: try decode with symbol shift -%d", shiftcount + 1);
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res = decodeWithShift(params, magsn, nbSymbolBits, r174, comments, -1);
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}
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shiftcount++;
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}
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}
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if (res == 0)
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{
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if (comments == "LDPC fail")
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{
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@ -108,4 +132,45 @@ void ChirpChatDemodDecoderFT::decodeSymbols(
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}
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}
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int ChirpChatDemodDecoderFT::decodeWithShift(
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FT8::FT8Params& params,
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std::vector<std::vector<float>>& mags,
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int nbSymbolBits,
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int *r174,
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std::string& comments,
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int shift
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)
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{
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if (shift > 0)
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{
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for (unsigned int si = 0; si < mags.size(); si++)
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{
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for (int bini = (1<<nbSymbolBits) - 1; bini > 0; bini--)
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{
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float x = mags[si][bini - 1];
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mags[si][bini - 1] = mags[si][bini];
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mags[si][bini] = x;
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}
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}
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}
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if (shift < 0)
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{
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for (unsigned int si = 0; si < mags.size(); si++)
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{
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for (int bini = 0; bini < (1<<nbSymbolBits) - 1; bini++)
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{
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float x = mags[si][bini + 1];
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mags[si][bini + 1] = mags[si][bini];
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mags[si][bini] = x;
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}
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}
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}
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float *lls = new float[mags.size()*nbSymbolBits]; // bits log likelihoods (>0 for 0, <0 for 1)
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std::fill(lls, lls+mags.size()*nbSymbolBits, 0.0);
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FT8::FT8::soft_decode_mags(params, mags, nbSymbolBits, lls);
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return FT8::FT8::decode(lls, r174, params, 0, comments);
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}
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#endif // HAS_FT8
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@ -21,6 +21,10 @@
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#include <vector>
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#include <string>
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namespace FT8 {
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class FT8Params;
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}
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class ChirpChatDemodDecoderFT
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{
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public:
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@ -39,10 +43,20 @@ public:
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std::string& call1, //!< 1st callsign or shorthand
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std::string& call2, //!< 2nd callsign
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std::string& loc, //!< locator, report or shorthand
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bool& reply , //!< true if message is a reply report
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bool& reply, //!< true if message is a reply report
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int& payloadParityStatus,
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bool& payloadCRCStatus
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);
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private:
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static int decodeWithShift(
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FT8::FT8Params& params,
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std::vector<std::vector<float>>& mags,
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int nbSymbolBits,
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int *r174,
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std::string& comments,
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int shift = 0
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);
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};
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