BTS_Tests: f_rtpem_activate(): pad TCH/FS frames with 'FF'O

Since recently [1], osmo-bts started to preen incoming FR and EFR RTP
frames for SID errors.  In other words, if an incoming frame is a SID
frame, osmo-bts may modify some bits causing a mismatch on our side.

Use 'FF'O as padding pattern for TCH/FS to prevent pseudo-random frames
being treated as SID and modified by osmo-bts.  Keep using '00'O for
other modes, because only TCH/FS specific SID frames must have specific
bit positions set to '0'B;  for TCH/EFS and TCH/HS it's '1'B.

Change-Id: Ib42b783574caf5cbaf64b2eb5dd1d2b2a6637c2f
Related: [1] osmo-bts.git I89df2f12c49dd5378667cf149d19bde654f80134
Related: OS#6039
1 file changed