Pre-Roll Just Got More Complicated

By Rob Leishman, Marketing Manager, Abit.
Managing the delay or pre-roll in a transmission path means an automation system has to begin playout of material slightly in advance to ensure the broadcast of all elements of the channel start on time.
The more complex, flexible and imaginative the channel image becomes the more timing issues need to be resolved and managed by the automation system. Add the up and down conversion between SD and HD into the mix and the addition of new features like split screen channel branding and pre-roll just got a lot more complicated for the average automation system.
The first part of the workflow is to get all of the programme material and branding elements transferred into the transmission environment ready for playout. A lot of automation systems rely on the media asset management system to supply material to the transmission server for playout at the correct time. This is rather like 'expecting something in the post.' Problems in transfer are invisible to the transmission environment and can not easily be rectified and what happens if you need to make a last minute change to the schedule?
For this reason, the ideal scenario is where the automation system is responsible for moving file based material from the IT domain into the transmission domain. Then, the operator in the transmission suite remains in overall control and has the tools to monitor and step-in and cancel and restart the transfer should it be too slow or if there is a fault elsewhere in a peripheral device or in the network architecture preventing delivery on time.
To achieve this, the automation system needs to be designed to prioritise the transfer of material making use of multiple FTP sessions over a broadband Ethernet. The sessions are managed by the automation system while the broadband Ethernet connects a range of equipment including transmission, archive and file based servers along with graphics play-out devices.
In the event that there is insufficient time to complete the file transfer, a device API is used to set up a TCP/IP connection allowing play-out of the file while in the background the remainder of the file is transferred.
These transfers are time dependant but the real complexity is when the timing has to take into account the device characteristics. Time delayed play-out of a channel can simply be recorded and shifted by a fixed time delay with commercial opt-outs allowing different commercial material to be played out with fixed linkage of channels. When the secondary channel needs to be reformatted to meet regulatory issues, then it becomes much more complex.
Firstly the channel needs to be reformatted automatically to meet the host country's regulations for different commercial slot timing and placement. Secondly, operational or schedule changes need to be reflected correctly in the secondary channels. Thirdly, any changes - such as moving the channel logo - that overlaps information embedded in the play-out material or changes the aspect ratio need to be addressed. It is only possible to manage the increased complexity of this workflow with complete accuracy if the automation system retains control of the movement and insertion of material.
Pre-roll traditionally was starting play-out a fixed number of frames early on a VTR so that mechanically everything was operating optimally before play-out. However, these days, play-out is much more challenging as the workflow in the transmission path is not fixed but adaptive dependant on both network performance and the material type resulting in variable delays depending on the routing. The best way to manage this added complexity is with an automation system that gives the operator one point of control.
Abit’s Present-it automation system has been developed in this way to meet the needs of the increasingly complex workflow that we see in broadcast environments today.
For more information visit: www.abit.co.uk
(BMcN)