Boolean MPEG2TransportStreamIndexFile::rewindToVSH(unsigned long&ixFound) {
Boolean success = False;
while (ixFound > 0) {
if (!readIndexRecord(ixFound)) break;
u_int8_t recordType = recordTypeFromBuf();
if ((recordType&0x80) != 0 && (recordType&0x7F) <= 2/*GOP*/) {
if ((recordType&0x7F) == 2) {
// This is a GOP. Hack: If the preceding record is for a Video Sequence Header,
// then use it instead:
unsigned long newIxFound = ixFound;
while (--newIxFound > 0) {
if (!readIndexRecord(newIxFound)) break;
recordType = recordTypeFromBuf();
if ((recordType&0x7F) != 1) break; // not a Video Sequence Header
if ((recordType&0x80) != 0) { // this is the start of the VSH; use it
ixFound = newIxFound;
break;
}
}
}
// Record 'ixFound' as appropriate to return:
success = True;
break;
}
--ixFound;
}
if (ixFound == 0) success = True; // use record 0 anyway
return success;
}
Boolean MPEG2TransportStreamIndexFile::rewindToCleanPoint(unsigned long&ixFound) {
Boolean success = False; // until we learn otherwise
while (ixFound > 0) {
if (!readIndexRecord(ixFound)) break;
u_int8_t recordType = recordTypeFromBuf();
setMPEGVersionFromRecordType(recordType);
// A 'clean point' is the start of a 'frame' from which a decoder can cleanly resume
// handling the stream. For H.264, this is a SPS. For H.265, this is a VPS.
// For MPEG-2, this is a Video Sequence Header, or a GOP.
if ((recordType&0x80) != 0) { // This is the start of a 'frame'
recordType &=~ 0x80; // remove the 'start of frame' bit
if (fMPEGVersion == 5) { // H.264
if (recordType == 5/*SPS*/) {
success = True;
break;
}
} else if (fMPEGVersion == 6) { // H.265
if (recordType == 11/*VPS*/) {
success = True;
break;
}
} else { // MPEG-1, 2, or 4
if (recordType == 1/*VSH*/) {
success = True;
break;
} else if (recordType == 2/*GOP*/) {
// Hack: If the preceding record is for a Video Sequence Header, then use it instead:
unsigned long newIxFound = ixFound;
while (--newIxFound > 0) {
if (!readIndexRecord(newIxFound)) break;
recordType = recordTypeFromBuf();
if ((recordType&0x7F) != 1) break; // not a Video Sequence Header
if ((recordType&0x80) != 0) { // this is the start of the VSH; use it
ixFound = newIxFound;
break;
}
}
}
success = True;
break;
}
}
// Keep checking, from the previous record:
--ixFound;
}
if (ixFound == 0) success = True; // use record 0 anyway
return success;
}
int MPEG2TransportStreamIndexFile::mpegVersion() {
if (fMPEGVersion != 0) return fMPEGVersion; // we already know it
// Read the first index record, and figure out the MPEG version from its type:
if (!readOneIndexRecord(0)) return 0; // unknown; perhaps the indecx file is empty?
setMPEGVersionFromRecordType(recordTypeFromBuf());
return fMPEGVersion;
}
Boolean MPEG2TransportStreamIndexFile
::readIndexRecordValues(unsigned long indexRecordNum,
unsigned long& transportPacketNum, u_int8_t& offset,
u_int8_t& size, float& pcr, u_int8_t& recordType) {
if (!readIndexRecord(indexRecordNum)) return False;
transportPacketNum = tsPacketNumFromBuf();
offset = offsetFromBuf();
size = sizeFromBuf();
pcr = pcrFromBuf();
recordType = recordTypeFromBuf();
return True;
}
