Doesn't really matter what transmission mode is used - you still need to record and play back at a higher speed. Both carrier frequency and the actual message being transmitted would be slowed down, as determined by the relativistic Doppler shift.

If the ship is racing away at 99% lightspeed, the message would be received at a frequency of 1/14 the original, and be slowed down to 1/14 the original speed.

__________________
"We do not require reality to conform to the expectations of the ignorant"