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There are two levels of alignment inside clearmode RTP packets carrying CSData per TS 48.103 section 5.6: 1) Alignment of 2 or 4 V.110 (T) or pseudo-V.110 (NT) frames within one RTP packet of 160 octets of an imaginary ISDN B channel; 2) For NT modes only, alignment of 4 pseudo-V.110 frames to form a single 240-bit RLP frame. Per previous patch, alignment 1 is to be treated as mandatory for RTP transport inside an Osmocom network. Alignment 2 _could_ be made mandatory for TCH/F9.6 NT, but the same is not possible for TCH/[FH]4.8 NT: in the best case of half-alignment, alternating RTP packets will carry alternating halves of RLP frames. Implemented solution: allow arbitrary state of alignment 2 (aligned or misaligned) in the incoming RTP stream for all CSD NT modes, and perform the necessary alignment internally. This approach is consistent with the world of E1 BTS: a TRAU in data mode is responsible for alignment 1 (with 20 ms TRAU frames taking the place of our clearmode RTP packets), but only the BTS can perform alignment 2, as the TRAU is agnostic to T vs NT distinction. Related: OS#6579 Change-Id: Idaebfce6da13b23ba265a197502712d83991873e