In Broadcast - October 2019 - 46

46

www.inbroadcast.com | Vol: 9 - Issue 9 | October 2019

InForm

Immersive Audio at the
2020 Tokyo Olympics
The 2020 Tokyo Olympics is just around the corner, Mike Kahsnitz
takes a look at how audio is produced and distributed at this event...

T

he 2020 Olympics is closing in
on us, and it is of course very
interesting to be looking at how audio
is produced and how it is distributed
from the Olympics to broadcasters
around the world. Not least is it
important to us to dig into how we
can help ensure that audio quality is
maintained in production as well as
through transmission lines.
Practical Life
But one thing is the technology,
another thing is how it is used in
practical life. Through discussions
with a number of TV sports channels
we have found that 16 channels is
the commonly required format for
transmission of sports in general, and
this is the official format that will be
used by OBS (Olympic Broadcasting
Services) at the Olympics 2020, too.
OBS is the organization responsible
for the production of all official audio
and video from the Olympics, live
television, radio or digital coverage.
All audio at the 2020 Olympics will
be produced using 16 audio channels,
and the relatively new Dolby® Atmos™
format will lay the ground for how
those 16 audio channels are laid out.
Though metadata is known to be
part of Dolby Atmos, there will be
no metadata delivered by OBS, as
they will be transmitting immersive
discrete audio.
Audio Channel Layout
Though all audio will be produced
in an immersive audio format,
broadcasters can subscribe to channel
layouts from stereo all the way up to
5.1.4 with additional audio objects, and
here I'd like to zoom in on the formats
in use. There will be two immersive
channel layouts at play. Both are based

on a traditional 5.1.4 main- and upper
bed layout, but they differ with regards
to stereo channels and the number of
objects.
The first layout (below) has two
stereo pairs plus two audio "objects".
The other layout (below) has only
one stereo pair, but four objects.
Content
The 5.1 main bed is a traditional
5.1 surround layer that contains no
metadata. Even without metadata,
normal panning can of course occur,
though panning is likely to be static.
The upper bed represents 4 ceiling
mounted, down pointing speakers.
Also here there is no metadata, and
most likely static panning.
The 5.1.4 would be containing a
traditional mix of the atmosphere, for
instance the ambience in a football
stadium.
The stereo channel(s) could for
example contain the same ambience,
but in stereo.
The objects could be as simple as
just static international commentary
or other static audio. As mentioned
before, the transmission from the
Olympics will carry no dynamic
metadata, though the Dolby® Atmos™
format supports it.

Immersive audio format

Is there a Loudness
standard for this?
There are a number of international
standards for measuring stereo and
surround audio, and you
might wonder if there is
also one for immersive
audio.
The answer is yes. ITU 1770 in its
latest version 4 (ITU-R BS. 1770-4)
covers the most popular configurations
and weighting factors for measuring
audio layout formats up to 22.2.
TouchMonitor and Immersive Audio
With its simple and flexible user
interface and the capability to
monitor up to 32 audio channels
simultaneously, TouchMonitor very
much fits the needs to monitor
immersive audio streams, and with
a selection of form factors, it will
prove itself is useful to engineers
on production as well as engineers
downstream.

RTW TM9 TouchMonitor
5.1 (main bed) - 4.0 (upper bed) - 2.0 + 2.0 (2 x stereo) - two objects

5.1 (main bed) - 4.0 (upper bed) - 2.0 (stereo) - four objects

In Kahsnitz's next blog he will
discuss what parts of the immersive
audio signal needs to be monitored,
how they should be monitored and
how to set up a TouchMonitor for that
purpose.

Explainers:
Dolby Atmos: For those of you who
are new to this, Dolby® Atmos™ is the
name of a surround sound technology
developed by Dolby Laboratories, and
the technology supports up to 128
audio channels.
On top of the audio channels
themselves,
the
Dolby
Atmos
technology
allows
engineers
to add associated spatial audio
description metadata to the audio
channels. An audio channel that
includes metadata is called an
audio object.
MPEG-H: The MPEG-H 3D audio
system was developed by Fraunhofer
based on the ISO/IEC Moving Picture
Experts Group (MPEG) standards
to support coding audio as audio
channels, audio objects, or higher
order ambisonics (HOA).
MPEG-H 3D Audio can support up
to 64 loudspeaker channels and 128
codec core channels.
Channels,
objects,
and
HOA
components may be used to transmit
immersive sound as well as mono,
stereo, or surround sound.
The MPEG-H 3D Audio decoder
renders the bitstream to a number of
standard speaker configurations as
well as to misplaced speakers.
Binaural rendering of sound for
headphone listening is also supported.
Objects may be used alone or in
combination with channels or HOA
components.
The use of audio objects allows
for interactivity or personalization
of a program by adjusting the gain
or position of the objects during
rendering in the MPEG-H decoder.
NHK 22.2: Beside the 16 audio
channel immersive audio format
discussed above, NHK, the main
Japanese national broadcaster, will do
an additional transmission using 24
audio channels, 22.2.
22.2 is the surround sound
component of the new television
standard Super Hi-Vision.
It has been developed by NHK
Science
&
Technical
Research
Laboratories and uses 24 speakers,
including two subwoofers, arranged in
three layers + LFE: Upper layer: nine
channels, middle layer: 10 channels,
lower layer: three channels and two
LFE channels.
Super Hi-Vision will be produced
from a limited number of venues and
for limited distribution.
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