Access Unit and AUD in Transport Stream

What data should an access unit contain?

    [SPS][PPS][IDR][PFrame][BFrame]

is an access unit? I got the concept that, access unit delimiters are required in ts packet. But, if the source file(I am using .264 file as input) do not contain AUD? then should I add AUD explicitly? If yes, then of how many bytes? Should it be the following?

    0x00000169(of Header+1 Byte)

And where should I add the AUD? Currently my TS file contains this formation:

    [TS Header][PES Header][SPS][PPS][IDR][PFrame][BFrame][TS Header]...

Is this structure okay? Also, can one access unit contain multiple I frames?

f the source file does not contain AUD should I add AUD explicitly?

YES

Also, can one access unit contain multiple I frames

No, an an access unit is analogous to a single frame, they are used to explesit delimit frames. Hence the name.

0x00000169(of Header+1 Byte)

0x00000169FF80 just use this for the AUD. You can hard code it.