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TECHNOLOGY
|
THE CHANNEL
THE CHANNEL
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JANUARY08
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53
ONLINE AND ARCHIVE STORAGE
Five nodes of Isilon disc storage,
totalling 40 terabytes, are accessible
for online storage. Everything so
far as possible incorporates
redundancy, including main and
backup Mediator databases, main
and backup servers. Ingest is split
across two servers so only half of
each is lost if a server goes wrong.
A 12-drive Sony Petasite
LTO3000 based data tape archive
provides sufficient capacity for up
to 18 months of MXF 50i
programmes. Multiple transcoders
and multiple data movers interface
between the servers and the
Petasite. Each LTO3000 takes LTO3
data tape cassettes with a capacity
of 400 gigabytes per cassette. Each
server controls four Petasite drives.
If one server goes down, the eight
other drives would continue
working. DigiBeta tapes are still
held as backups with the option of
making local or external copies.
MEDIATOR OUTGEST
Mediator manages outgest of
video, files and metadata to any
chosen destination using an XML
interface for metadata. Outgest 1 is
DigiBeta, Outgest 2 is Digital
Rapids Version X, and so on.
Outgest to graphics is handled
similarly, exporting clips directly
into a Pixel Power Clarity for
making promotional graphics.
Quite a lot of material is issued
on DVD for the Channel 4 press
office. This is transcoded from 50i
and a logo superimposed. A Pharos
database within Mediator makes a
title slate which is added to the
DVD chapters. Transcoders are
used to generate 15 long-GOP files
for transmission from Pinnacle
servers. All broadcast schedules for
a week or more go into the
Mediator and that actually drives
the transcode process.
TRANSITIONAL TIMESCALE
The project was anticipated to take
15 months from start to finish. It
began about the time when
affordable storage costs combined
with a growing need to get the
media out to the right places. It
would have been too expensive a
year earlier. Channel 4 wanted a
system big enough to handle at
least a year's programmes. The
Petasite has sufficient capacity to
store 12 to 18 months of content.
Channel 4 launched its 4oD
video-on-demand service a year
ago, supplying Tiscali, BT Vision,
Virgin Media and the PC download
service. The video-on-demand
requirement came shortly after
installation commenced and meant
rescheduling some priorities. Half
the system was allocated to deliver
the 4oD service and the rest of the
system is essentially complete.
Time could have been saved by
opting for IMX rather than MXF.
Starting today, one would certainly
go down the MXF route as it is
finally becoming fully supported
by equipment suppliers. There was
no rigid deadline to meet and it
was important not to end up with
several years of content that would
need rewrapping in the future. It was
Main Image:
Channel 4’s
headquarters in
London
Top left:
Part of
the Pharos
Mediator
managed data
storage system in
the C4 library
area
Top right:
Task-
specific Pharos
Mediator Spot
Check user
interface
planned that each MXF file should
be standalone and potentially
readable very far into the future.
The Media Access Project greatly
simplifies media ingest and
outgest. Pharos did a detailed
study of workflow within each
relevant department of Channel 4.
Mediator enabled a starting
workflow pattern to be defined for
each operator. The ability to
reconfigure workflow was also
very important. The system has
certainly met expectations,
streamlining day-to-day workflows
and increasing overall efficiency. It
has also made engineering planning
for additional services much easier.
The system itself is very scalable,
allowing more storage to be added
whenever required.
THE FUTURE
For Channel 4's recently launched
HD simulcast service on the Sky
platform, the first phase has
parallel HD ingest to a separate
Omneon server which takes HD
and SD for short-term storage and
playout. HD content is stored on its
original master tapes and only
compressed for actual transmission.
Direct ingest of data files is
clearly the future. An increasing
number of commercials already
arrive at Channel 4 from a server at
the end of a line. For programmes,
standards and delivery costs are the
issues. With three or four
Hollyoaks
per week, for example, it is far
cheaper to put tapes on a bike and
send them down from Liverpool
rather than wire them as files. The
move to HD makes wired delivery
of archive-quality programmes
even more challenging but that is
obviously the future.
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