Joining M2TS files from different sources

[TCmullet]

I'm making my first serious attempt to create an X264 file (m2ts) to join to a file captured by the Hauppauge Colossus.  All is 1920x1080i.  I discovered that my Virtualdub can encode X264 in an AVI.  Then I remux with AviDemux to .M2TS.

When I then use AviDemux 2.6.5 (r8897) to join them (with the soft-encoded piece first), it appears to join.  But then I load the result into AviDemux and the indexing stops at the end of the soft-encoded piece.

Without being an X264 encoder expert (I've largely left most settings at default), is there a list somewhere of x264/h264 encoding parameters that have to be the same for AviDemux to recognize them as compatible for purposes of joining them (appending them)?

I really need to be able to create H264 M2TS files that I can join with files directly encoded by the Colossus.
I've done the obvious things like pixel ratio, audio format parameters.

[mean]

i would check if the pid used are the same
i.e video ix 0x150 for the 1st one and 0x151 for the 2nd
Mediainfo will tell you

[TCmullet]

i would check if the pid used are the same
i.e video ix 0x150 for the 1st one and 0x151 for the 2nd
Mediainfo will tell you

Under Video, I see:
ID: 256 (0x100)
in both of them.

I don't why they should be different, especially as all the clips I normally join are all from the Colossus and have the same values anyway, not different ones.  Can you please clarify what you mean in light of what I'm reporting here?