42 / 48
52
|
JANUARY08
|
THE CHANNEL
THE CHANNEL
|
TECHNOLOGY
C4MEDIAACCESS
UK Channel 4 Television has completed the first phase of its
media access project, progressing C4 from video tape to an
MXF file-based operation.
Kevin Burrows
,C4’s CTO and
Spencer Rodd
, Technical Director at
Pharos
, explain about one
of the most innovative technical progressions in C4’s 25 years
IMX so that file-users could
simply unwrap metadata stored
with each file rather than needing
to rely on a database. MXF 50i
also makes decoding much
easier as no additional software
is required.
INGEST
Incoming programmes and
interstitials are ingested at full 50
Mbit/s I-frame MPEG2 via Omneon
ingest servers to an Isilon central
online storage system before being
automatically transcoded to 15
Mbit/s Long GOP MPEG2 for
playout via the existing Pinnacle
TX server system. Using Mediator,
Channel 4 is able to perform the
entire broadcast operation from its
online digital library store.
The ingest area is equipped with
quality control booths for content
that needs careful eyeballing and
fast-track desks for material that
does not need to be viewed in real
time. Both are controlled via
Mediator. All ingested content is
exported to the browse system
through MPEG1 encoders at the
same time as it is transferred for
transmission. The browse system
is used for off-air logs, for all
compliance viewing and for
checking of commercial break
running order. A playlist function
is already built in. A generic
Application Program Interface is
used to ensure flexible control.
With
25 years of
archived
material,
it is
important
to be as
future-
proof as
possible
“
”
n 2003 Channel 4 replaced
its VHS-based preview
facility with a Pharos
browse system giving
access directly from
standard desktop office
PCs. The objective was to
deliver browse-quality content to
relevant staff as efficiently as
possible with minimal operational
overheads. This would bring the
further benefit of eliminating the
risk of lost or damaged video tapes.
The result was a highly co-ordinated
solution centred on a Pharos
Mediator media management
database. Initially rolled out to 20
desktops and expanded later to
400, this proved very successful
and is one of the largest broadcast
browse systems in Europe.
The media access project was a
logical extension of the browse
concept, effectively adding in a
single architecture all the facilities
Channel 4 needed for file-based
ingest, long-term storage and
playout. Essentially a large library
of file-based digital content and
metadata, it allowed the channel to
create and maintain a tapeless store
of all programmes which could
then be made available in any
format, whether linear TV, video on
demand, mobile or whatever might
be called for in the future.
PHAROS MEDIATOR AT C4
The entire media access project -
ingest server, content store, archive
manager, Petasite tape library and
file transfer management - are
managed by the Pharos Mediator
media management system and
database.
Pharos Mediator is a scalable
broadcast media management
system which can be configured to
co-ordinate single or multiple
workflows in any broadcast
environment. Ingested content can
be catalogued, researched, loaned
and shared between users,
providing collaborative working.
Files can be outgest to any selected
format, such as complete
programmes music compilations
for post-production or DVDs for
local distribution. Multiple client
libraries can be configured to
provide security and privacy for
clients without the expense and
complexity of separate hardware
for every client.
FILE FORMAT
An initial challenge was the
selection of a generic file format.
MXF 50i was chosen on the basis
that it maintains optimal quality
and is a relatively easy standard to
export. If the need arises to send
content elsewhere, recipients will
be able to use the programme
content and the accompanying
metadata. Many broadcasters have
gone down the road of proprietary
IMX. Channel 4 wanted to avoid
I
PROJECT