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#1761 DMR decoder supports Hytera Tier 3 UTF-16 Talker Alias & new Traffic Channel Talker Status CSBKO 47. Implements a tracking feature to detect when vendors are playing games using non-standard CSBK CRC mask values by tracking when a non-standard mask value is consistently detected and applying that mask when the initial CRC check fails.

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Dennis Sheirer
2023-12-14 07:10:30 -05:00
parent b6c6505824
commit ec9ceeefb3
13 changed files with 400 additions and 32 deletions
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49
src/main/java/io/github/dsheirer/edac/CRCDMR.java
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@@ -1,18 +1,21 @@
/*******************************************************************************
* sdr-trunk
* Copyright (C) 2014-2018 Dennis Sheirer
/*
* *****************************************************************************
* Copyright (C) 2014-2023 Dennis Sheirer
*
* 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 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.
* 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/>
*
******************************************************************************/
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>
* ****************************************************************************
*/
package io.github.dsheirer.edac;
import io.github.dsheirer.bits.BinaryMessage;
@@ -177,6 +180,28 @@ public class CRCDMR
return 2;
}
/**
* Calculates the residual CRC value using a mask of zero which should identify the mask value when an alternate
* mask value is employed.
* @param message to be checked
* @param messageStart location
* @param crcStart location
* @return residual CRC check value.
*/
public static int calculateResidual(CorrectedBinaryMessage message, int messageStart, int crcStart)
{
int calculated = 0; //Starting value
/* Iterate the set bits and XOR running checksum with lookup value */
for(int i = message.nextSetBit(messageStart); i >= messageStart && i < crcStart; i = message.nextSetBit(i + 1))
{
calculated ^= CCITT_80_CHECKSUMS[i - messageStart];
}
int checksum = getIntChecksum(message, crcStart, 16);
return calculated ^ checksum;
}
/**
* Error detection for CRC-9 protected Confirmed Packet Data blocks. These
* data blocks have a slightly complicated structure because the checksum