In MA1 mode, delay the P3 logical channel to match P1

[argilo]

In service mode MA1, a diversity delay of 3 frames is applied to the P1 logical channel (specifically targeting the BL and BU subframes on the transmit side). As a result, the P1 logical channel has an additional 3 frames of latency and the receiver must delay the ML and MU subframes before deinterleaving so that all subframes have a combined (TX + RX) delay of exactly 3 frames.

The P3 logical channel does not have a diversity delay. To keep the received data aligned with the P1 logical channel (so that the core & enhanced streams can be coherently combined), it is necessary to apply an additional 3-frame delay in the receiver. I've accomplished that here by applying a 3-frame delay to the EL and EU subframes that carry the P3 logical channel.

No change is required for service mode MA3, because its P3 logical channel already has a 3-frame delay applied to the EML and EMU subframes, complementing the transmitter's 3-frame delays to the EBL and EBU subframes.

[argilo]

I also replaced the magic number 18000 in a bunch of places, because not all subframes have the same length.

[argilo]

One downside to delaying the entire P3 logical channel is that a secondary program (i.e. HD2) or AAS data contained in this logical would be unnecessarily delayed. We could avoid that by moving the delay up to layer 2 and selectively applying it to the enhanced stream, but I'm not sure it's worth it. It would be interesting to see which approach hardware receivers take.