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kkboy1
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LeAudio

Dataset card Data Studio Files
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value name description
x single once play the current track once
x single repeat play the current track repeatedly
x in order once play all of the tracks in a group in track order
x in order repeat play all of the tracks in a group in track order then repeat
x oldest once play all of the tracks in a group once in ascending order of age
x oldest repeat play all of the tracks in a group in ascending order of age then
repeat
x newest once play all of the tracks in a group once in descending order of
age
x newest repeat play all of the tracks in a group in descending order of age then
repeat
x shuffle once play all of the tracks in a group once in random order
xa shuffle repeat play all of the tracks in a group once in random order then
repeat
table playing order characteristic values
there are a couple of nuances in these t he first two values which play the current track
x and x set the current track to the next track when they have completed or been
stopped for shuffle the randomisation is left to the implementation in most cases the
implementation is not tota lly random but weighted as listeners do not expect the same tracks
to be played close together at the start of a subsequent cycle these decisions are left to the
implementation the client simply sends the command if the server cannot support the
requested playing order for example when it doesnt know the age of the tracks it should
ignore the command
chapter telephony and media control
as with the media control point characteristic a client can determine which playing order
features are supported by reading the playing orders sup ported characteristic this is a
octet bitfield with the bitfield meanings shown in table
value name
x single once
x single repeat
x in order once
x in order repeat
x oldest once
x oldest repeat
x newest once
x newest repeat
x shuffle once
x shuffle repeat
table meaning of bits in the playing orders supported characteristic
thats it for telephony and media control our next stop is volume audio input and
microphone
section mcs and mcp
chapter volume audio input and microphone control
chapter volume audio input and microphone control
anyone who has worked on audio specifications will probably tell you that a large part of their
time was taken up with discussions about volume control its a topic which generates even
more debate than audio quality the reason for that is twofold the first is a never ending
and generally academic discourse on the perception of volume and how to define the steps
between minimum and maximum the second is how to cope with multiple different ways of
controlling the volume the second problem didnt ex ist when you had a single volume knob
on your tv or amplifier however as soon as you have multiple remote controls it became
increasingly challenging for a user to work out how to set the volume
after the requisite hundreds of hours of debate the bluetooth le audio working groups
decided to more or less skip the first problem and concentrate on the second how to
coordinate multiple different points of control so this chapter is all about volume control
with only a passing reference to how volum e is interpreted because thats left to the
implementation well also cover microphone control as its analogous but involves the input
of audio rather than its output all of these features are designed to be used on non encoded
audio signals in the case of volume that means after reception and decoding for the
microphone control service and profile it is before transmission
volume and input control
after the previous chapters this should be plain sailing there are three services involved
with volume and one profile
the volume control service vcs which can be viewed as the main volume
control knob
the volume offset control service vocs which can be considered as a
balance control
the audio input control service aics which allows individual gain control and
mute on any number of audio inputs which dont need to be bluetooth audio
streams and
the volume control profile vcp which lets multiple clients control the se
services
although most of these have volume in their name what they actually do is adjust the gain
ie the amplification of the audio signal
section volume and input control
figure typical implementation of volume and audio input services for a headphone
figure shows a typical implementation for a pair of headphones or banded hearing
aids which ha s three possi ble audio inputs a bluetooth audio stream a telecoil audio
input and a microphone input these inputs are mixed together using the audio input
cont rol service to set their individual gains and to selectively mute and unmute them the
resulting stream has its gain controlled by the volume control service setting if the stream
is a stereo one then once it is split into its left and right component s a separate instance of
the volume offset control service can adjust the gain going to each speaker the drawing
is a hardware representation in practice the sum of vcs and vocs gain settings are
applied to each audio channel used together differe ntially these mimic the effect of a
balance control they can also be used individually to adjust the relative level of sound in
each speaker to accommodate different levels of hearing loss in the left and right ear
coping with multiple volume control s
from the outset during bluetooth le audio development it was obvious that users would
want to control the volume of their earbuds and headset from multiple different places the
assumption was that there would be local controls on the earbuds volume controls on the
audio sources typically the phone as well as separate volume controls in smart watches and
other dedicated remote control devices
to make this level of distributed control work you want to keep the primary volume control
at the device which is rendering the audio if you dont but let it be controlled at the audio
source as well you can end up with one controller operating on the source level and one on