Since there are no formal documents available for implementing gstqamtunersrc, some of the features are very vague.
Below is some description on the important features.

PAT insertion:
gstqamtunersrc inserts an artificially generated PAT at intervals mandated by ISO-13818-1 specification. The original PAT broadcast in the transport stream has multiple programs in it. The output of gstqamtunersrc is a single program transport stream (SPTS) and only the requested program must be present in the PAT tables sent out. This is the reason why we artificially generate them instead of letting the original PAT pass through.


PMT insertion:
The PMT acquisition is managed by RMFQAMSrc and in-band SI manager. gstqamtunersrc is not privy to this information. In order to include the relevant PMT in the outgoing SPTS, RMFQAMSrc copies the PMT section from in-band SI manager and passes that to gstqamtunersrc as a property. gstqamtunersrc wraps this section in a TS packet and sends it out at regular intervals.


TTS:
Enabling TTS switches gstqamtunersrc's TS output packet size from 188 byte to 192 byte. The additional bytes are used to embed a timestamp indicating what time that packet was generated. This timestamp is used by the player to synchronize A/V.