1. A new technique for low cost, near real time IP
based audio distribution for community radio
CBAA National Conference
Chris Deacon
Vice President
General Manager
Engineering & Development
November 2007
© ArtSound Incorporated

2. IP audio streaming
Allows audio connections to be established over LAN/WAN and internet
environments.
– Permits near real time applications
– Low latency (No significant delays).
Allows for cost effective audio distribution from anywhere to anywhere
– As long as a reliable internet connection is available
Amount of digital information that is needed to represent high-quality raw
digital audio requires several Megabits per second
– Therefore digital audio is compressed to allow transmission via Internet.
Several different IP Audio compression methods and protocols are available
(such as MP3 and AAC).
– There are cost and quality tradeoffs along with some common problem areas
and risks .
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3. Audio via IP
An IP audio system digitizes and reformats the original audio, codes and/or compresses the
data, adds IP address information to each packet, transfers the packets through the Internet,
recombines the packets and extracts the digitized audio, decodes the data and converts the
digital audio back into its original audio form.
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4. Digital Distortion
Audio signals are digitized, compressed and error protection coded prior to
transmission. During the transmission process, some packets are lost or corrupted –
can result in the temporary interruption of the audio signal. Because data compression
process represents sounds by different codes, packet corruption alters sound that was
originally transmitted. If significant data corruption occurs, this can create unusual
sounds (artifacts, “warbling”, or “smearing”).
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5. Digital Audio Quality Issues
Crosstalk
Digital Audio Quality (DAQ)
Noise Level
Key Quality Indicators (KQI)
Signal to Noise Ratio (SNR)
Bit Error Rate (BER)
Quality of Experience (QoE)
Packet Loss Rate (PLR)
Connection Success Rate
Packet Delay Variation (PDV)
(CSR)
Audio Fidelity
Connect Time
Mean Opinion Score (MOS)
Buffer Time
Frequency Response (FR)
Rebuffer Events
Total Harmonic Distortion (THD)
Rebuffer Time
Latency
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6. Audio IP Features
Unlike ISDN or POTS codecs, Audio IP:
can be implemented in software or lower cost hardware
will run on an inexpensive PC or in most cases a laptop
can use existing high-speed Internet connection (LAN or
3G bandwidth from a phone, wireless datacard, wireless
router/modem).
no additional charges other than standard Internet data
charge - you can stay connected all month but pay only
for data sent; unlimited plan may be best option.
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7. Audio IP features (cont)
Many ISP’s offer upstreaming of data at no volume charge!
Each link requires one transmit unit and one receive unit
(or software application)
The effects of packet loss on the transmission of streamed
audio over Internet protocol (IP) can be mitigated by the
inclusion of redundancy in the transmitted stream.
Buffer ensures that temporary glitches or connectivity
issues with your Internet connection will not affect the
high-quality audio connection from the transmit end to the
receiver. Latency is an important issue for live radio.
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8. Audio IP Applications
Inexpensive outside broadcasts - quality good enough
to send stereo music and speech from the OB site back
to the studio.
Studio To Transmitter (STL) links - a cost effective
alternative to RF links with high-quality audio from the
Studio to Transmitter and a telemetry link back to the
studio for confidence monitoring.
Link distant facilities for transfer of audio feeds from
one computer to the other - distance no object.
Easy to setup and operate and can be operated on
virtually any Internet ready computer with reasonable
sound card.
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9. Instreamer
Real time audio encoder
Audio streaming encoder with multiple operating modes (push/
pull, http, RTP etc), control via webbrowser or open API (UDP,
TCP, cgi or serial). SNMP monitoring for device supervision.
Configurable MP3 encoding (8kbit to 192kbit VBR, 16-48kHz
sample rate), G.711 (aLaw/uLaw) and 16bit PCM (both 8 and
24kHz sample rate). Network interface: 10/100Mbit Ethernet.
Audio Inputs: 2-channel stereo, analog (RCA), coaxial and optical
S/PDIF. Headphone output. Control: IR output, serial RS-232 port.
Power supply: 9..30VDC /12..24VAC.
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10. Extreamer
Real time audio decoder
Audio streaming decoder with multiple operating modes
(push/pull, http, RTP etc), control via web browser or open API
(UDP,TCP, cgi or serial). USB memory interface.
Supports MP3 (up to 320kbit/s FBR & VBR) and WMA (5-384kbit/s).
Network interface: 10/100Mbit Ethernet, audio outputs:
2-channel stereo analog (RCA and headphone).
Control: optional IR receiver for IR remote, serial RS-232 port.
Power supply: 9..30VDC /12..24VAC.
©ArtSound Incorporated
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11. Instreamer/Exstreamer devices
Allow
unidirectional, low latency, high quality audio distribution over
satellite or terrestrial IP systems.
They support
RTP/Multicast, and can also transport control signals.
Backup/emergency STL; OB; No PC required at either end
Instreamer encodes the audio in real time, the stream is
distributed via the internet and at the remote sites, the IP feed
received is decoded into audio and control by the Exstreamer.
The Exstreamer can be controlled to select one of multiple
channels.
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12. Instreamer/Exstreamer audio
Using realtime MP3 encoding, achievable audio quality better than CD at 192
kbps max. in highest quality settings. Compression rate can be increased and
sample rate can be set lower so a typical “FM” stereo audio signal can easily
be streamed at 128 kbps.
Barix IP Audio products are standalone, hardware based devices which are
easy to set up, low power (<6 W power consumption), based on embedded
technologies (non-PC architecture) and low cost.
A typical STL link setup can be achieved with one Instreamer and Exstreamer
at a total cost of approx. $700 (not including the DSL line or equipment).
A single Instreamer can serve up to 8 concurrent streams allowing multiple
transmitter sites with Exstreamers to be linked.
Instreamer can also serve to stream to an Icecast/Shoutcast server for internet
radio applications, or provide a stream into an audio recording solution
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13. RTP reliability
RTP (Real Time Protocol) - a stream of UDP frames containing audio
content plus a small header with time sequence information.
– used by the receiving party (e.g. Exstreamer) to detect and replace lost
frames.
If Exstreamer detects lost frame(s), it will replace the missing audio
information with repetition(s) of the next incoming frame.
Sound quality is good because the replacement is usually short and fits well
into its surrounding audio.
– Even with massive packet loss, music and speech are still intelligible.
– Rhythm of music or speech can be preserved even when packets are lost
during transmission.
RTP is an Internet standard
– is interoperable with a wide range of other RTP supporting applications and
hardware devices.
BRTP – a Barix variation to facilitate easier use behind LAN firewalls
©ArtSound Incorporated
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14. IP Multicasting Project
A non-profit subscriber-supported digital audio service
for remote and/or isolated Australian citizens
Seniors confined to nursing homes
and hospices
Handicapped or infirm confined to
home or hospital
Dwellers in remote and underserved
rural/outback areas
Retirement homes
Disadvantaged citizens denied ready
access to health, social and
educational services
Uses innovative internet multicast
streaming audio technology
Local, regional and national
components
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15. Features
Builds on existing community
radio expertise,
infrastructure and content
Largely volunteer driven:
users have the opportunity
to participate directly in the
service as program
presenters and organisers
Content tailored to regional
and local communities
National distribution with
regional/local hubs
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16. Project Consortium
Initial “core” partners are five of
Australia’s community FM radio
stations (Fine Music Network):
ArtSound FM Canberra
2MBS FM Sydney
3MBS FM Melbourne
4MBS FM Brisbane
5MBS FM Adelaide
Act as regional distribution/production
centres in NSW, Vic, Qld, SA, ACT
regions
• WA, NT, Tas, to be added later
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17. How does it work?
Uses low cost, next generation IP-
based technology to encode, distribute
and decode in real time
Point to multipoint IP streaming over
the internet (or digital sub-carriers in
metropolitan area)
– restricted to private users
Uses an intelligent network-based
audio decoder that can pull digital
audio from multiple IP network sources
and convert it to audio.
Software-controlled switchover to
alternative streaming sources, such as
regional or locally originated programs
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18. Technical Configuration
Easy and simple internet based
distribution
– No expensive satellite dish, no
dedicated Telco lines
– No broadcast licences required
INTERNET
ENCODER
Localised content customisation
– per region, town or subscribing
organisation
Inexpensive and simple installation
DECODER DECODER
and usage
– Plug a small decoder device
into the broadband network
Compatible with IP based LAN,
WLAN technology
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19. User hardware
Simple, easy to install decoders
Cost ~ $300-500
No PC required
No complicated software
Fed by LAN or direct from ADSL
modem/router
Feeds existing domestic audio or
hospital broadcast distribution PA
equipment, or wireless LAN
No tuning or antennas required
No training course necessary
High quality stereo audio
Remote programmable from program
origination centre
©ArtSound Incorporated
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20. Further information?
chris.deacon@artsound.com.au
or 02-6295-7444
©ArtSound Incorporated
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