Grass Valley M-Series iVDR Service Manual - Manual (Page 21)

6 July 2004 M-Series Service Manual 21
Media control and processing
the Windows file system) that controls access to the raw data that makes up each
file. Any reading and writing of clips, be it through play and record operations or
through file transfers and media streaming, is managed by the database. The
database also contains iVDR configurations and logs. The database and file system
run as Windows programs.
The Storage System includes the media disk drives, controllers, drivers, and adapters
necessary for access and movement of the data. While the primary data flow is within
the overall control of the Real Time System, some components and their
communication pathways cross over into the Application System. For example, the
SCSI controller resides on the RTP board, yet it is controlled by Windows. The media
drives appear as the V: drive to the Windows operating system.
The Real Time System manages the media flow between the Storage System and the
iVDR inputs and outputs. The Real Time system has a dedicated processor and
time-sensitive mechanisms to serve media processing needs while maintaining
real-time accuracy.
When you control iVDR play and record operations from within the Application
System you trigger a chain of events that eventually crosses over into the Real Time
System and results in media access. The following sequence is an example of this type
of chain of events:
1. A user operates the Player application to play a particular clip. The Player
application communicates with the Media File System to initiate play access to the
clip.
2. The database identifies the files that make up the clip and the file system instructs
the Storage System to open access to the files.
3. The Storage System finds the raw data and opens the appropriate read access. At
this point both the Application system and the Real Time system are involved.
Windows controls the media drives and controllers, so the Real Time system
makes file requests to Windows and it causes the data to be transferred to buffers
on the Real Time Processor. The data is then available to the Real Time System so
that it can be processed at exactly the right time.
4. The Real Time System processes the media, decompresses it, adjusts its timing,
and moves it as required to play the clip as specified by the user.