| |
IPTV: Can you afford to
forget about the sound?
Other Topics:
August 21, 2007
"Debate about IPTV systems very often lead to discussions about
the choice of video coder. But whilst next generation video coders
like H.264 and Windows Media are undoubtedly playing a vital
enabling role in new IPTV services, the choice of video coder is not
the only critical coding decision to make before rolling out a
platform."
- Jason Power, Director, Broadcast Systems, Dolby
Audience expectations of quality surround audio have never been
higher thanks to the success of DVD, so it’s important that IPTV
platforms incorporate the appropriate audio technology to enable
them to deliver the right audio features now and in the future. |
|
|
|
|
|
|
A New Expectation
The standard audio format for DVD is Dolby Digital 5.1 – a
cinema-style surround sound format that envelops the viewer and
places them at the centre of the action thanks to the use of 6
speaker channels in place of the usual two. The popularity of this
format on DVD has led to significant sales of home cinema audio
systems in key markets worldwide. For example, over 17.5m home
cinema systems have been sold in Europe, with 17% of households in
the important UK, German, Dutch and French markets estimated to own
a system even by the end of 2005. [source: Understanding and
Solutions]. This in turn has driven a new expectation of quality
surround audio from by viewers – which has not gone unnoticed by the
broadcast industry. Leading pay TV operators such as Canal Plus,
Premiere and Sky are amongst the European broadcasters who have
already launched digital TV services complete with Dolby Digital 5.1
surround sound. Other entertainment sources are also featuring
surround sound – for example, games consoles such as the Xbox can
generate live real time 5.1 soundtracks that immerse players in
their games. And whilst 5.1 sound is a valuable added feature to
standard definition media, it’s even more important with high
definition – it’s a key feature both of existing HD services in the
US and the newly launched services in Europe. So with the
expectations of viewers set so high, can IPTV operators really
afford to ignore the audio?
IPTV Challenges
Many IPTV implementations have significant data-rate constraints,
which on first consideration might make it seem difficult to find
the extra bandwidth needed to transmit the extra audio channels
needed for 5.1. However, adding 5.1 audio doesn’t always require as
much bandwidth as first thought. Firstly, it’s not necessary to
deliver separate 5.1 and stereo audio streams. Even though the
set-top box needs to output soundtracks in 5.1, stereo and mono to
suit viewers with different equipment, with Dolby Digital a single
data-efficient 5.1 audio stream is delivered to each set-top box and
downmixed inside to create any stereo or mono outputs needed.
Secondly, next generation audio coders like Dolby Digital Plus have
been designed specifically to partner with new video coders like
H.264, offering even more attractive data rates for audio to match
the savings for video. This means that home cinema audio can be
delivered using data rates practical for IPTV.
5.1 audio can be more of a challenge, however, if it is not planned
in from the start. A key consideration is that the right audio
technology needs to be included in IPTV set-top boxes from the
beginning of deployment. If the right technology is not included at
the outset, operators who subsequently decide to offer 5.1 might end
up having to ‘simulcast’ separate stereo and 5.1 audio streams to
ensure that all viewers can receive audio. It’s also critical that
good connectivity is provided to output the encoded 5.1 audio stream
to viewers’ existing home cinema systems. As many home cinemas only
have inputs for encoded digital audio (rather than decoded
multichannel audio), it’s important that the connection format is
supported by the maximum number of systems to maximise the audience
that can enjoy full surround sound.
Sourcing 5.1 programming
Once a platform has been deployed with 5.1 capability, the next step
is to source appropriate content. Fortunately, over 7500 movies have
been produced in Dolby Digital 5.1, and almost all Hollywood titles
and major domestic releases are now created in the format. And, due
to the demand for 5.1 soundtracks on DVD and increasingly on
broadcast services, entertainment series such as Lost, ER and 24
plus premium programming like natural history and documentaries are
being produced with thrilling 5.1 sound.
Broadcasters are also starting to add the excitement of surround
sound to their premium sports coverage. For example, events as
varied as the Superbowl and German Bundesliga soccer have been
produced and broadcast live in 5.1, transporting the viewer at home
right into the middle of the action.
To The Future
Audio is already perhaps more important in the marketing of TV
services than it has ever been before. But the future brings further
possibilities – delivery of soundtracks with 7.1 or even more
channels, multiple language versions, streamed director commentaries
to be overlaid over the main soundtrack, and improved audio for the
visually- and hearing-impaired to name but a few.
But for today, it’s critical to note that the audience already has
an expectation for home cinema audio with their TV entertainment,
not internet quality audio. Fortunately, if the audio solution used
by their IPTV supplier has been chosen carefully, they won’t be
disappointed. |
|
Back to Newsroom |
|
