Theatre Design & Technology - Fall 2020 - 20

consider frame rate. How fast do those
pixels need to change color and intensity?
If a system is running at 30 frames per
second, this is different from 60 frames
per second, meaning pixels potentially
change at a faster rate. This also impacts
the performance requirements for the
computer.

Maxin10sity's " Pandora's
Box " entry in the 2019
LUMA Festival, projected
onto 79 Collier Street, in
Binghamton, NY. | Photo
by Mark Doyle/ USITT.

2. Encoding guidelines

Video files are typically very large and
encoded using a compression scheme,
known as a codec. The codec choice
will impact computer operation, because
some codecs rely more on the capabilities of the CPU, while other codecs rely
more on the capabilities of the graphics
card, or GPU. Uncompressed video files
place more demand on the computers
and require more " bandwidth, " as well as
storage. It is preferable to compress files
into something more compact and manageable. Codec selection impacts the performance requirements, and whether the
CPU or the graphics card plays a greater
role.
Typically, a particular media server
platform will have guidelines for encoding to achieve the best results. It's
important to know which platform is
being used and the associated encoding
guidelines. Additionally, there may be different terminology used for the same parameters among different platforms and
codecs. For example, in WATCHOUT,
bi-directional frames are called B-frames,
but in other platforms B-frames may be
called N-frames or M-frames.

3. Frame sync and genlock

Synchronization is another important
consideration for multi-output media
servers. The graphics card, let's say it's
a 4-output or 6-output card, will usually
have resident software synchronization
capability. However, hardware-assisted
synchronization is required under certain
circumstances, so the addition of a " sync
card " to facilitate frame sync, or genlock
using a signal generator, may be necessary to perfect a seamless appearance
across multiple display devices. This may
be especially true when networking multiple servers together.
An LED wall with multiple LED
processors is just one example of an application that requires hardware-assisted
sync. The goal is to have pixel-to-pixel
synchronization across the entire wall

20 | THEATRE DESIGN & TECHNOLOGY | FALL 2020

regardless of the number of processors.
Also, multiple projector blends with less
than 15 percent overlap may sometimes
require hardware-assisted sync.
For scenic projection on a stage or
when projecting on buildings, the projection surfaces are fairly imperfect.
Viewers are less likely to see the visual
imperfections caused by less-than-ideal
frame synchronization. In contrast, when
a number of monitors are configured in a
video wall, all butted up against each other with no bezel, a totally seamless look
is important. Hardware assist adds that
necessary frame synchronization.

4. Content complexity

Demanding applications require more
digital horsepower. An arena concert
with a lot of fast-moving content and multiple simultaneous cross-fades would use
more computer resources than relatively
static applications like scenic projection
in a live theatre production.
Also, some of the processes might
be handled outside of the computer. For
example, some newer professional-grade
projectors can communicate with each
other; they network together and perform
edge-blending within the projectors so

that the media server doesn't need to. It
becomes a balance between the resources being used in the computer versus the
built-in features of the projector. So if you
are using a light-duty server, it may be
beneficial to try to edge-blend with the
projectors first, if that capability exists.

5. EDID management

Several other elements affect the hardware and performance requirements of
your media server. For example, EDID
(Extended Display Identification Data)
management helps maintain a functional
connection to the display devices in the
event of a signal loss or glitch somewhere
in the signal chain. Higher-end graphics cards typically have the capability for
EDID emulation. Most of the time, using
the on-board EDID management capability works just fine, although it is another
point of system resource usage. With a
light-duty media player, you may wish
to use a stand-alone EDID manager for
each display device.

6. Live capture

Another feature that may be desirable
is live capture input. Traditionally, this is
handled by adding capture cards to the

Theatre Design & Technology - Fall 2020

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