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;
}
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;
}
void MPEG2TransportStreamIndexFile
::lookupTSPacketNumFromNPT(float& npt, unsigned long& tsPacketNumber,
unsigned long& indexRecordNumber) {
if (npt <= 0.0 || fNumIndexRecords == 0) { // Fast-track a common case:
npt = 0.0f;
tsPacketNumber = indexRecordNumber = 0;
return;
}
// If "npt" is the same as the one that we last looked up, return its cached result:
if (npt == fCachedPCR) {
tsPacketNumber = fCachedTSPacketNumber;
indexRecordNumber = fCachedIndexRecordNumber;
return;
}
// Search for the pair of neighboring index records whose PCR values span "npt".
// Use the 'regula-falsi' method.
Boolean success = False;
unsigned long ixFound = 0;
do {
unsigned long ixLeft = 0, ixRight = fNumIndexRecords-1;
float pcrLeft = 0.0f, pcrRight;
if (!readIndexRecord(ixRight)) break;
pcrRight = pcrFromBuf();
if (npt > pcrRight) npt = pcrRight;
// handle "npt" too large by seeking to the last frame of the file
while (ixRight-ixLeft > 1 && pcrLeft < npt && npt <= pcrRight) {
unsigned long ixNew = ixLeft
+ (unsigned long)(((npt-pcrLeft)/(pcrRight-pcrLeft))*(ixRight-ixLeft));
if (ixNew == ixLeft || ixNew == ixRight) {
// use bisection instead:
ixNew = (ixLeft+ixRight)/2;
}
if (!readIndexRecord(ixNew)) break;
float pcrNew = pcrFromBuf();
if (pcrNew < npt) {
pcrLeft = pcrNew;
ixLeft = ixNew;
} else {
pcrRight = pcrNew;
ixRight = ixNew;
}
}
if (ixRight-ixLeft > 1 || npt <= pcrLeft || npt > pcrRight) break; // bad PCR values in index file?
ixFound = ixRight;
// "Rewind' until we reach the start of a Video Sequence or GOP header:
success = rewindToCleanPoint(ixFound);
} while (0);
if (success && readIndexRecord(ixFound)) {
// Return (and cache) information from record "ixFound":
npt = fCachedPCR = pcrFromBuf();
tsPacketNumber = fCachedTSPacketNumber = tsPacketNumFromBuf();
indexRecordNumber = fCachedIndexRecordNumber = ixFound;
} else {
// An error occurred: Return the default values, for npt == 0:
npt = 0.0f;
tsPacketNumber = indexRecordNumber = 0;
}
closeFid();
}
Boolean MPEG2TransportStreamIndexFile::readOneIndexRecord(unsigned long indexRecordNum) {
Boolean result = readIndexRecord(indexRecordNum);
closeFid();
return result;
}
void MPEG2TransportStreamIndexFile
::lookupPCRFromTSPacketNum(unsigned long& tsPacketNumber, Boolean reverseToPreviousCleanPoint,
float& pcr, unsigned long& indexRecordNumber) {
if (tsPacketNumber == 0 || fNumIndexRecords == 0) { // Fast-track a common case:
pcr = 0.0f;
indexRecordNumber = 0;
return;
}
// If "tsPacketNumber" is the same as the one that we last looked up, return its cached result:
if (tsPacketNumber == fCachedTSPacketNumber) {
pcr = fCachedPCR;
indexRecordNumber = fCachedIndexRecordNumber;
return;
}
// Search for the pair of neighboring index records whose TS packet #s span "tsPacketNumber".
// Use the 'regula-falsi' method.
Boolean success = False;
unsigned long ixFound = 0;
do {
unsigned long ixLeft = 0, ixRight = fNumIndexRecords-1;
unsigned long tsLeft = 0, tsRight;
if (!readIndexRecord(ixRight)) break;
tsRight = tsPacketNumFromBuf();
if (tsPacketNumber > tsRight) tsPacketNumber = tsRight;
// handle "tsPacketNumber" too large by seeking to the last frame of the file
while (ixRight-ixLeft > 1 && tsLeft < tsPacketNumber && tsPacketNumber <= tsRight) {
unsigned long ixNew = ixLeft
+ (unsigned long)(((tsPacketNumber-tsLeft)/(tsRight-tsLeft))*(ixRight-ixLeft));
if (ixNew == ixLeft || ixNew == ixRight) {
// Use bisection instead:
ixNew = (ixLeft+ixRight)/2;
}
if (!readIndexRecord(ixNew)) break;
unsigned long tsNew = tsPacketNumFromBuf();
if (tsNew < tsPacketNumber) {
tsLeft = tsNew;
ixLeft = ixNew;
} else {
tsRight = tsNew;
ixRight = ixNew;
}
}
if (ixRight-ixLeft > 1 || tsPacketNumber <= tsLeft || tsPacketNumber > tsRight) break; // bad PCR values in index file?
ixFound = ixRight;
if (reverseToPreviousCleanPoint) {
// "Rewind' until we reach the start of a Video Sequence or GOP header:
success = rewindToCleanPoint(ixFound);
} else {
success = True;
}
} while (0);
if (success && readIndexRecord(ixFound)) {
// Return (and cache) information from record "ixFound":
pcr = fCachedPCR = pcrFromBuf();
fCachedTSPacketNumber = tsPacketNumFromBuf();
if (reverseToPreviousCleanPoint) tsPacketNumber = fCachedTSPacketNumber;
indexRecordNumber = fCachedIndexRecordNumber = ixFound;
} else {
// An error occurred: Return the default values, for tsPacketNumber == 0:
pcr = 0.0f;
indexRecordNumber = 0;
}
closeFid();
}
