MediaSonic MS9000, Руководство пользователя

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HD Player Chapter 14: Application Notes
85 Rev. 6.4
Chapter 14: Application Notes
The following sections contain some application specific notes to help the system designer and installer use the
MediaSonic HD Player in 3D or multi-channel configurations.
Synchronized playback
The MediaSonic HD Player has been designed to support applications requiring multiple HD sources. Typical
uses of this feature include, High Resolution 3D displays or multi-source shows with soft edging.
There are two control conditions that need to be met before a system can playback synchronously. Firstly the
players must start at the same time and secondly they must playback locked together in a condition known as
Genlock. These concepts are discussed later in this chapter.
Content Preparation
The first requirement for a multi-source system is that the content being displayed is “correct” on all Players.
There are certain constraints that MPEG streams must operate within to ensure successful synchronization. The
most important of these is that the first frame of the stream is an I frame and follows a Group of Pictures header
(for a discussion of these terms please refer to the MPEG appendix). This is easy to implement when using a
software encoder, but may prove difficult if using an encoder linked to a tape machine. Most of the currently
available “Broadcast quality” encoders are designed to stream to an uplink transmitter and do not usually have the
ability to frame accurately encode, or record to a storage medium such as disk.
Since most systems will use a Genlock signal that will be either 29.97Hz or 25Hz it is necessary that the frame
rate of the content also be one of these frequencies.
Genlock
The genlock features in the HD Player can be used to ensure the output rasters from the multiple units stay locked
together. This ensures that once the units begin playing the output video will stay synchronized. In a closed system
it is only necessary to designate one Player as the Genlock Master and the rest as Genlock Slaves. Genlock will
keep the units playing in sync. relative to each other but they also need to start at the same time, see the following
sections for information on timecode triggers.
Playing in Sync. with Timecode
The only guaranteed way to trigger a multi-channel show is to use the timecode input. The timecode can come
from an external generator or one of the HD Players can be used to generate the timing reference. The timecode
‘Start’ point is set on the Master player a few seconds in advance of the ‘Play At’ timecode that is set identically
on both Master and Slave. The separate timecode section of this manual contains a detailed description of the
timecode capabilities and explains how to set up a timecode trigger on both the Master and the Slave(s).
The timecode trigger is set up using a “cue” or “play range” command from an external control system before the
timecode feed starts counting. See Cueing and Playing with Serial Control below.
Cueing and Playing with Serial control
Before a system will ‘trigger’ from a timecode point the Players must be ‘Cued’ and sent a ‘Play’ command. On
receipt of the ‘Play’ command the Master Player will start to generate timecode. When the ‘Play At’ timecode
point is reached all players will start.