feature iptv
Multi-channel
audio over IP
Surround sound, an essential component of the cinema experience,
has found its way into the home. James Caselton - broadcast
marketing manager at Dolby, considers the challenge this poses to
IPTV networks.
A
truly immersive audio For broadcasters who have already bandwidth restricted delivery systems.
experience can transport deployed Dolby technologies in their However, as HE-AAC is an open
someone to another broadcast systems, the most likely standard, not all implementations will
world, fill them with favoured option will be to move to survive the careful scrutiny of the
expectation or make the Dolby Digital Plus for its backwards broadcaster or operator. To help
hairs on the back of their compatibility with the existing Dolby ensure quality of service, broadcasters
neck stand on end. Sound is an Digital 5.1-channel home theatre must take care to maintain control
essential component in setting the systems already in use and its ability over their transmitted content,
scene, creating the background tension
Above: James
to scale up in terms of bit rate whichever audio codec they choose.
and building the atmosphere upon
Caselton, broadcast
(3Mbits/s and beyond) and discrete Are broadcasters sure that their
which video thrives.
marketing manager
channels (7.1 or more) with improved content is being delivered to
In order to maintain this convincing
at Dolby.
bit rate efficiency. customers with the intended audio
illusion, the audio must be of high Dolby Digital Plus is included in the quality?
quality both in terms of its Digital Video Broadcasting (DVB) One solution is to combine HE-AAC
performance and its continuity. Today, specifications for HD and other digital technology with audio metadata, a
more than ever before, the surround TV services. technology pioneered by Dolby and
sound experience is a vital part of the already deployed within Dolby Digital
entertainment experience. Audio codec choice for and Dolby Digital Plus on other
Affordable HD televisions can be broadcasters broadcast platforms to ‘describe’ the
matched with home theatre systems
Broadcasters
audio stream in such a way that the
to faithfully recreate the cinematic and For those broadcasters who have not decoder can be directed to optimise
illusion for the front room. Multi-
operators...
yet deployed any Dolby technologies the received performance to the
channel audio delivery is increasingly
being seen by audiences as a vital part
recognise the
in their broadcast systems, HE-AAC consumer. Audio metadata can offer
of their home entertainment platform -
growing
could provide another option where significant improvements in decoder
efficient bandwidth utilisation is stability, error concealment and
be it delivered over terrestrial, satellite,
importance of
critical. overall audio quality as it tailors the
cable, packaged media or IP. audio Whereas Advanced Audio Coding sound to the receiver’s capabilities,
Surround sound, an essential
metadata for
(AAC) is a perceptual coding method enabling a single 5.1 stream to handle
component of the cinema experience,
controllable,
used to compress digital audio for multi-channel, stereo, and mono
has found its way into the home.
As delivery over IP grows in
predictable
efficient storage and transmission, HE- signals with seamless switching. This
popularity many are asking if a fully
and consistent
AAC adds spectral band replication eliminates the need for bandwidth
(SBR) to dramatically improve quality consuming simulcasting.
immersive audio experience can be
high quality
and efficiency at lower bit rates. As a Dolby Pulse is Dolby’s latest audio
delivered as part of the overall audio. result, HE-AAC can offer 5.1 solution and combines HE-AAC audio
package. The simple answer is yes. The multichannel audio at 160 kbps, near coding with Dolby’s industry standard
next generation audio codec solutions CD-quality stereo at 32 kbps, excellent- audio metadata technology (the same
must offer the broadcaster/operator a quality stereo at 24 kbps, and good metadata technology deployed in
careful balance between quality, quality for mixed content even below Dolby Digital and Dolby Digital Plus). In
consistency, reliability and efficiency. 16 kbps for mono - making it ideal for a broadcast landscape that now
22 l ibe l January/February 2009 l www.ibeweb.com
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