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Fixed CRC calculation for TS Packets, in particular the PAT

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This commit is contained in:
Erik Zandvliet 2014-11-17 14:45:07 +01:00
parent 7bf5b4093b
commit fc080f81ca
2 changed files with 13 additions and 13 deletions
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8
lib/checksum.h
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@ -219,10 +219,10 @@ namespace checksum {
0x6D66B4BCU, 0xDA7B75B8U, 0x035D36B5U, 0xB440F7B1U
};
while (len > 0) {
crc = table[*data ^ ((crc >> 24) & 0xff)] ^ (crc << 8);
data++;
len--;
const char * tmpData = data;
const char * end = tmpData + len;
while(tmpData < end){
crc = table[((unsigned char) crc) ^ *tmpData++] ^ (crc >> 8);
}
return crc;
}

18
lib/ts_packet.cpp
View file

@ -919,20 +919,20 @@ namespace TS {
return ((int)(strBuf[loc]) << 24) | ((int)(strBuf[loc + 1]) << 16) | ((int)(strBuf[loc + 2]) << 8) | strBuf[loc + 3];
}
/// \todo checksum is calculated wrong, but the stream plays. Fix checksum when deadlines are less tight.
void ProgramMappingTable::calcCRC() {
unsigned int loc = 4 + (AdaptationField() > 1 ? AdaptationFieldLen() + 1 : 0) + getOffset() + 13 + getProgramInfoLength() + (getProgramCount() * 5);
unsigned int loc = 4 + (AdaptationField() > 1 ? AdaptationFieldLen() + 1 : 0) + getOffset() + getSectionLength();
unsigned int newVal;//this will hold the CRC32 value;
unsigned int pidLoc = 4 + (AdaptationField() > 1 ? AdaptationFieldLen() + 1 : 0) + getOffset() + 9;;//location of PCRPID
newVal = checksum::crc32LE(0, strBuf.c_str() + pidLoc, loc - pidLoc);//calculating checksum over all the fields from table ID to the last stream element
unsigned int pidLoc = 4 + (AdaptationField() > 1 ? AdaptationFieldLen() + 1 : 0) + getOffset() + 1;//location of PCRPID
INFO_MSG("Calculating checksum from offset %d, over %d bytes", pidLoc, loc - pidLoc);
newVal = checksum::crc32(-1, strBuf.c_str() + pidLoc, loc - pidLoc);//calculating checksum over all the fields from table ID to the last stream element
if (strBuf.size() < 188) {
strBuf.resize(188);
}
strBuf[loc] = (newVal >> 24) & 0xFF;
strBuf[loc + 1] = (newVal >> 16) & 0xFF;
strBuf[loc + 2] = (newVal >> 8) & 0xFF;
strBuf[loc + 3] = newVal & 0xFF;
memset((void*)(strBuf.c_str() + loc + 4), 0xFF, 180 - loc);
strBuf[loc + 3] = (newVal >> 24) & 0xFF;
strBuf[loc + 2] = (newVal >> 16) & 0xFF;
strBuf[loc + 1] = (newVal >> 8) & 0xFF;
strBuf[loc] = newVal & 0xFF;
memset((void*)(strBuf.c_str() + loc + 4), 0xFF, 184 - loc);
}
///Print all PMT values in a human readable format