Why does Tvheadend deliver data over TCP to Showtime? I thought it was bad to use TCP for realtime sensitive traffic?
  'HTSP' - the protocol used for streaming TV, sending meta information updates and RPC between Tvheadend and Showtime uses a transmission scheduler with multiple queues on the Tvheadend side. This means that Tvheadend can measure the available bandwidth between itself and the mediaplayer and when congestion happens it's even capable of dropping less important data (such as B-frames). HTSP has been tested over WAN links and DSL connections with zero picture/audio artifacts.

  It's possible to get view drop statistics and bitrates directly in Showtime. (Open the menu when watching a TV-channel and switch on 'Detailed Information')