One of the important features of a video recorder is the ability to deal with
programme schedule changes and to ensure that the wanted programme is always
recorded. TVAnytime has its own set of data descriptors to handle late-running
or cancelled programmes but these are not used by Freeview Plus. Instead the
Running Status from the now/next section of the EIT is used to start and stop
the recording.

VDR can control timers from the running status by using 'VPS' functions in
conjunction with this patch. Note however that the normal VPS operation will no
longer work.

To use VPS for accurate recording, some conditions must be met:

- VDR must be compiled with the 'VPS Fallback' patch (included with this
  plugin). Note that some Linux distributions (eg. Mageia) include
  this patch in their binaries. 
- Parameters 'UseVps' and 'VpsFallback' in setup.conf must both be set to 1
- Timers must have the 'use VPS' flag set
- The start time of a timer must be set to exactly the scheduled start time of
  the programme (ie no padding).

With these conditions met, the sequence of events is:

- Shortly before the scheduled time of the recording (set by 'VpsMargin' in
  VDR's setup.conf) VDR switches to the multiplex containing the channel to be
  recorded
- VDR monitors the running status of the programme to be recorded
- When the running status changes to 'running', VDR starts recording
- When the running status changes to 'not running', VDR stops recording and
  deletes the timer.
- If the programme has not started by the time it was scheduled to finish,
  monitoring is stopped and the timer is deleted.

CAUTIONS
- VPS recordings seem to have a lower priority than live viewing. VDR
  will not interrupt live viewing to start looking for the start of a recording.
- The recording will not be made correctly if the wanted programme is not
  'next' on the channel at (expected start time - VpsMargin), so do not set 
  VpsMargin too high.