Grass Valley UIM v.2.1.1 - Manual (Page 149)

February 5, 2008 UIM Instruction Manual 149
MXF transfers via FTP
When receiving an MXF stream, the UIM parses the structural metadata and uses it
to decompose the stream into its various elementary essences, such as video, audio,
and timecode. Once the essence is extracted, it is either written to the file system
(UIM-SAN-GEIP or UIM-SAN-FCIP), or assembled into a GXF stream for transfer
to a standalone Profile (UIM-DIS-GEIP).
When creating an MXF stream from either a GXF stream or a clip on an Open SAN
file system, the UIM reformulates Profile clip metadata into MXF structural metadata
to ensure that the stream can be parsed by other MXF readers.
Descriptive metadata
Descriptive metadata includes information such as Producer name, name(s) of
actor(s), etc.
When receiving descriptive metadata within the MXF stream, the UIM does not retain
this information.
When generating an MXF stream, the UIM does not insert any descriptive metadata.
Any information of this type that was stored as Profile user data is inserted into a MXF
Dark Metadata KLV element, as mentioned below.
Dark metadata
The MXF standard allows for metadata that is not described by the standard to be
included as part of the MXF stream. This metadata is may be used for proprietary
purposes such as including scripts or scene information. Creating and reading dark
metadata is entirely the responsibility of the application that creates the clip.
When receiving dark metadata in the MXF stream, the UIM parses the metadata and
determines if it was originally Profile User Data, or if it came from some other source.
If it was Profile User Data, the UIM extracts the packets and identifies them as Profile
User Data, to be saved in the Profile format for such data. If the dark metadata came
from another source, the KLV information is stored as-is in Profile user data
extensions. The information remains part of the clip as long as the clip exists and can
be accessed by any application using relevant Profile User Data API calls
When creating an MXF stream, Profile User Data that was stored using the Profile
API as extensions is repackaged as with appropriate KLV information and included
in the stream. Incoming dark metadata associated with the clip that was stored as-is in
its KLV form is included as dark metadata in the stream, preserving its format exactly
as it was originally stored.
MXF transfers via FTP
An application can transfer a clip in the MXF format using the same FTP command
syntax as is used for GXF transfers. To initiate an MXF transfer, the specified
username must be mxfmovie, not movie as is used for GXF transfers.
The UIM always transfers essence in its original format. If it receives an MXF stream
that contains video essence in DVCPRO25, the resulting clip is stored in that format.
Similarly, MXF streams generated by the UIM always contain the same essence as
the clip to be transferred. If the clip’s video is recorded in MPEG Long GoP at
24 Mb/s, the video essence is included in the MXF stream in that format.