In Broadcast - September 2021 - 54

54
www.inbroadcast.com | Vol: 11 - Issue 9 | September 2021
InStudio
A Not-So-Deep Dive into
Audio CODECs
With Dr. Ciro Noronha, Executive Vice President
of Engineering for Cobalt Digital Inc.
L
et's talk about audio in the
context of broadcast encoders and
decoders. Many video compression
experts treat audio as a second-class
citizen - something that needs to be
done but does not merit a lot of attention
(to the chagrin of audio experts). But,
in
a
well-designed
system,
audio
cannot be an afterthought. It may
not be as compelling as video, but it
is equally important - bad audio can
greatly degrade an otherwise great
video experience.
Conceptually, audio is simpler than
video. You take in a signal with one
or more audio channels, compress the
whole thing, send it out, and, in the
other side the decoded audio should
sound pretty much the same as it did
when it came in (for most people who
are not audio experts). The reality
today is that all audio CODECs in use
today achieve the " sound pretty much
the same " part for the usual bit rates.
So, what is the big deal?
The big deal starts with multichannel
audio. Every audio CODEC in
use in broadcast today can do stereo.
That's par for the course, nobody
thinks about that. You have a left and
a right channel, they go in together
and come out in phase at the decoder.
Things start getting interesting when
you go to surround audio, where you
have more than two channels. That's
where we leave behind the good old
MPEG-1 Layer II (or III) CODEC. If you
have a 5.1 surround service (which is
actually composed of six channels),
couldn't we just use three
stereo
pairs of MPEG-1 Layer II? Not really
- you need to present all six channels
absolutely in phase. There are some
legacy systems that can do this, but
it is not part of the standard, and
such systems should be considered
proprietary as the channels are carried
independently. The far better way
9992-ENC/DEC
is to use an actual surround CODEC,
which will also save you bandwidth
(as it handles the .1 LFE channel more
efficiently), and will pack the whole
service into a single PID. Options for
that are the various Dolby CODECs,
as well as AAC (both LC and HE) and
MPEG-H. The same argument applies
to higher channel counts (such as
7.1) and the new object-based audio
CODECs.
Another aspect is multiple
languages. In this case, you have
multiple audio services, and each one
should go in a separate PID, with the
appropriate ISO 639-2 language code
so that receiving devices can honor
language preferences and play
the
correct audio.
9934-AUD-PRO-DSP
When you are deploying
a compression system,
it is important to pay attention to the
audio support. The Cobalt 9992-ENC/
DEC family is renowned for both the
breadth of CODEC support and the
number of simultaneous services.
Besides the usual support for MPEG-1
Layer II, Dolby AC-3/EAC-3, all flavors
of AAC, as well as LPCM, the 9992DEC
also supports Dolby AC-4 and
Dolby-E decoding.
If you need more
advanced processing, these can be
complemented by the 9934-AUD-PRODSP
or the 9904-UDX-4K-DSP, which
can add Real-Time Loudness Leveling
and automatic upmixing.
https://www.cobaltdigital.com
http://www.inbroadcast.com https://www.cobaltdigital.com https://www.cobaltdigital.com https://www.cobaltdigital.com https://www.brainstorm3d.com/products/edison?utm_source=inbroadcast&utm_medium=half%20page&utm_campaign=edison

In Broadcast - September 2021

Table of Contents for the Digital Edition of In Broadcast - September 2021

Contents
In Broadcast - September 2021 - Intro
In Broadcast - September 2021 - Cover1
In Broadcast - September 2021 - Cover2
In Broadcast - September 2021 - Contents
In Broadcast - September 2021 - 4
In Broadcast - September 2021 - 5
In Broadcast - September 2021 - 6
In Broadcast - September 2021 - 7
In Broadcast - September 2021 - 8
In Broadcast - September 2021 - 9
In Broadcast - September 2021 - 10
In Broadcast - September 2021 - 11
In Broadcast - September 2021 - 12
In Broadcast - September 2021 - 13
In Broadcast - September 2021 - 14
In Broadcast - September 2021 - 15
In Broadcast - September 2021 - 16
In Broadcast - September 2021 - 17
In Broadcast - September 2021 - 18
In Broadcast - September 2021 - 19
In Broadcast - September 2021 - 20
In Broadcast - September 2021 - 21
In Broadcast - September 2021 - 22
In Broadcast - September 2021 - 23
In Broadcast - September 2021 - 24
In Broadcast - September 2021 - 25
In Broadcast - September 2021 - 26
In Broadcast - September 2021 - 27
In Broadcast - September 2021 - 28
In Broadcast - September 2021 - 29
In Broadcast - September 2021 - 30
In Broadcast - September 2021 - 31
In Broadcast - September 2021 - 32
In Broadcast - September 2021 - 33
In Broadcast - September 2021 - 34
In Broadcast - September 2021 - 35
In Broadcast - September 2021 - 36
In Broadcast - September 2021 - 37
In Broadcast - September 2021 - 38
In Broadcast - September 2021 - 39
In Broadcast - September 2021 - 40
In Broadcast - September 2021 - 41
In Broadcast - September 2021 - 42
In Broadcast - September 2021 - 43
In Broadcast - September 2021 - 44
In Broadcast - September 2021 - 45
In Broadcast - September 2021 - 46
In Broadcast - September 2021 - 47
In Broadcast - September 2021 - 48
In Broadcast - September 2021 - 49
In Broadcast - September 2021 - 50
In Broadcast - September 2021 - 51
In Broadcast - September 2021 - 52
In Broadcast - September 2021 - 53
In Broadcast - September 2021 - 54
In Broadcast - September 2021 - 55
In Broadcast - September 2021 - 56
In Broadcast - September 2021 - 57
In Broadcast - September 2021 - 58
In Broadcast - September 2021 - 59
In Broadcast - September 2021 - 60
In Broadcast - September 2021 - 61
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In Broadcast - September 2021 - 75
In Broadcast - September 2021 - 76
In Broadcast - September 2021 - 77
In Broadcast - September 2021 - 78
In Broadcast - September 2021 - Cover3
In Broadcast - September 2021 - Cover4
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