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going to work a more practical solution which addresses the quality and universal access
requirements would be to transmit khz stereo and khz mono audio streams in one big
which only consumes around of the total airtime transmitting both a stereo khz pair
and a khz pair of audio streams in the same big takes the same airtime as a single khz
stereo st ream
in the examples above i have chosen the low latency qos settings despite that fact that
they include fewer retransmissions for the khz and khz sampling rates in this particular
application latency isnt that important as there are usually n o visual cues or simultaneous
ambient sound although there could be however in this application the broadcast
transmitter is likely to be placed high on a wall or attached to the ceiling to get the best
coverage so theres not much in the way to ab sorb the transmissions that should mean that
the low latency settings are adequate if the café owner located the broadcast transmitter in
a cupboard or under the serving counter that would be different this is something that
equipment designers need to think about in their physical design and installation instructions
ensuring that broadcast transmitters for this application can easily be wall mounted and that
any leads attached to a unit are long enough to do that
equipment manufacturers need to understand these constraints and design products with the
flexibility to support multiple bigs and allow the installer and venue owner to position and
configure them appropriately we should not expect café owners to understand airti me or
qos parameters manufacturers should provide them with solutions which are easy to install
and use that includes the ability to customise all of the ad type names and ltv strings
with values which are appropriate for each installation
chapter bluetooth le audio applications
a basic bro adcast transmitter which just accepts an audio input either from a mm jack
rca plug or a usb input is about as simple as you can get but will be adequate for very many
premises and applications equipment vendors will almost certainly provide more c omplex
broadcast units for larger establishments as well as managed services to configure them
supply the audio stream and integrate them into other audio services even with basic
bluetooth le audio broadcast there are plenty of opportunities for diff erentiation
tvs and broadcast
from an early point i n the bluetooth le audio development the tv industry became very
excited about the possibility of connecting tvs to earbuds headphones and hearing aids
although tvs can use unicast there is an obviou s limitation to its scalability as it requires
separate cises for every listener hence the consensus is that most tv usage will use
broadcast adding encryption to ensure that only authorised users can decode the audio
content in this section well look at the requirements for the three most common application
areas
public tv
today a large number of publicly installed tvs are silent its n ot because they have no audio
output but because they are installed in areas where ambient audio would be an noying or
conflict with other audio common examples are airports where operators dont want users
to be distracted from being able to hear flight and security announcements gyms where
multiple tvs display different channels but are silent as multipl e conflicting audio from them
would be cacophonous pubs and bars where the sound from even one tv and there are
often multiple tvs with different channels would disrupt normal conversation and outdoor
installations where the sound would not be heard or be intrusive
these installations are all akin to the simple broadcaster that we looked at above they dont
need encryption they just need a broadcast transmitter that could be a similar plug in device
attached to their tvs audio outputs or a bui ltin bluetooth le audio broadcast transmitter
it needs to allow a device location to be entered so that a user can match an audio broadcast
with the tv or it can take the wi fi route of sticking its access information on a notice on
the wall
as wev e seen above many of these devices including those integrated into tvs will probably
be managed not least to allow specific messages to be mixed into the audio stream for
example in an airport flight announcements would probably be mixed into an au dio stream
so that someone listening to a tv would never miss them this is where we will probably see
the start of multiple language streams if multiple language soundtracks are available for a tv
broadcast they can be sent in separate bises on one b ig using a khz mono coding it
should be possible to provide six different language streams from one broadcast transmitter
each input stream would mix the flight announcements in real time with the audio input for
that program with any unannounced l anguages being mixed at a subsequent point where they
section tvs and broadcast
dont conflict with any ambient announcements if a transmitter needed to support more
channels it could add a second bluetooth transmitter each language is identified by a
language ltv value in the base indicating the language of each bis a user can set their
scanning application to select specific languages so that these are presented preferentially
alternatively it can show all of the language variants which are available and let the user
choose the one they want to hear this requires the phone s apis to expose this information
and application developers to understand how to use it
personal at home
personal tv has different priorities many tvs already support bluetooth classic audio
profiles but that is generally limited to connecting to a soundbar a single set of earbuds or a
headphone the reality is that in most homes multiple members of the family or friends will
be listening although tv manufacturers could do a like forlike transition by moving the
bluetooth le audio unicast that will quickly hit an airtime limit of a few users it makes far
more sense to move to broadcast
unlike the public tv cases described above most users would not want their neighbours to
hear what they are listening to so for personal tvs and other audio sources in the home the
expectation is that broadcast audio streams would always be encrypted that means that
there needs to be a simple mechanism for the user to obtain the broadcastc ode to dec rypt
the audio streams
this is where the broadcast assistant comes in personal audio sources which expect to be
heard regularly by multiple users would expect each user to pair and bond with them that
provides a long term trusted connectio n when a user comes within range of the tv they
would ask their earbuds to connect and the broadcast assistant in the tv would inform them
of the broadcast stream location using past followed by the current broadcastcode this
is an important point once a user has paired they no longer need to use their phone to
connect to a broadcast when the user comes within range of the tv the basic le connection
can be automatic a pair of earbuds can be informed of that connection with an internally
gener ated audio message alerting the user to the presence of audio source if they want to
connect they press a button or perform whatever gesture the earbuds require allowing them
to receive the information they need from the tv to start audio streaming w ith no further
action from the user for users walking between rooms with different audio sources its an
elegant way for them to connect to the nearest source notifications are provided to all
broadcast assistant s informing them that the earbuds are d ropping synchronisation or
synchronising to a new source it means that every connected device which is involved keeps
track of the current status making it possible to engineer a very elegant solution
chapter bluetooth le audio applications
if friends come around and want to connect with t heir earbuds or hearing aids the tv owner