Figure 8: NMOS model (oversimplified)
SOURCE
FLOW
Video Grain
Data Grain
Audio Grain
INPUT LIST
Inputs are dynamic. As systems evolve and changes are made on
the fly, it is very hard to completely maintain an input list. Being up
to date takes paper and runners unless you’re using the same ex-
act spreadsheet. The use of “living document” applications such as
Google Sheets or Smartsheet allow all operators to have immediate
access to the current information, meaning everyone can now be on
the same sheet.
With AES67, your patching can be automated. You are never
changing the parameters of the transmitter with AES67; you are only
changing what is being received and where. If all of your multicast
sources were in a database, with metadata, it could be used to dy-
namically update your console’s inputs. When you realize that most
modern digital consoles are just database-driven analog console
emulators, you wonder why we’re still passing around paper input
lists with numbers instead of a database of raw, accurate data.
Figure 9: Google Sheet patch database with microphone
RECORDING
database and IP address/multicast address information for
every source
42 PROFESSIONAL SOUND
RECORDING
Sound recording is an electrical, mechanical, electronic, or digital
inscription of sound waves. In AES67, you have none of the above.
Data packets that contain transmissions are moved over a network.
Within those packets is a representation of the digital inscription but
the packet itself is not the inscription and, therefore, not a recording.
Wireshark could capture the “packet storm” that is on a network. If
all of those packets were intercepted and captured to a reliable and
readable capture format, one would accomplish the “recording” of
AES67. This process would capture the audio on the network without
any introduced signal processing, conversion, or dependence on
synchronization. The packets captured are individually time stamped
and could be re-assembled for playback. We’re not recording any-
more; we’re capturing.
Figure 10: PacketStorm - a network capture system
Anthony Peter Kuzub is the IP audio product manager for Toronto’s Ward-
Beck Systems (www.ward-beck.com) and is the vice chair of the Toronto
Audio Engineering Society.
He is actively involved in the technical and promotional aspects of the
Open Control Architecture (OCA-AES70) alliance and the Alliance for IP
Media Solutions (AIMS-ST2110). In his spare time, he is a carpenter that is
obsessed with automated test and measurement.