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doc: Add HFP design document

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Frédéric Danis 2012-11-15 18:35:39 +01:00 committed by Johan Hedberg
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Makefile.am
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@ -342,7 +342,7 @@ EXTRA_DIST += doc/manager-api.txt \
doc/media-api.txt doc/assigned-numbers.txt \
doc/supported-features.txt doc/alert-api.txt doc/mgmt-api.txt \
doc/oob-api.txt doc/proximity-api.txt doc/heartrate-api.txt \
doc/thermometer-api.txt
doc/thermometer-api.txt doc/audio-telephony-design.txt
AM_CFLAGS += @DBUS_CFLAGS@ @GLIB_CFLAGS@

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doc/audio-telephony-design.txt Normal file
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@ -0,0 +1,317 @@
Telephony Interface Design
**************************
Introduction
============
The aim of this document is to briefly describe usage of profile
interface which will allow external application to implement telephony
related profiles (headset, handsfree).
The goal
========
Previous version of headset code in BlueZ needs the implementation of an
AT parser for each modem target or external telephony application
(Maemo, oFono) which is not the aim of Bluez.
The profile interface allows BlueZ to focus on Bluetooth communication
part (connection, disconnection, authentication, authorization) and let
external application (i.e. oFono) take charge of the Telephony tasks (AT
parsing and modem specific code).
This will allow code to be simpler, easier to maintain and debug in both
BlueZ and telephony application.
Design
======
External applications, which should implement AT parsing and telephony part
will have to register an org.bluez.Profile1 agent using RegisterProfile of
org.bluez.ProfileManager1 interface.
This will setup a SDP record for the profile and a RFCOMM server
listening for incoming connection.
When a new device is connected, NewConnection method of Profile1 agent
is called with informations related to connecting profile (like RFCOMM
client file descriptor, version, features, media end point path, ...).
The telephony application is in charge to implement a MediaTransport for
its audio connection with remote device and interact with the
MediaTransport of the audio component (i.e. PulseAudio).
Flow charts
===========
Here is some flowcharts of interactions between BlueZ, telephony agent
(oFono) and audio component (PulseAudio):
.....> Bluetooth communication between headset and phone
-----> Dbus messages and signals
Start up
--------
When PulseAudio starts it registers media endpoints to BlueZ.
When oFono starts it registers profile agent for HFP.
PulseAudio BlueZ oFono
| | |
| register media endpoint | |
|------------------------>| |
| | register profile agent |
| |<-----------------------|
| | |
HFP Connection
--------------
On incoming connection, BlueZ performs (if needed) authentication and
authorization then passes RFCOMM file descriptor and media end point
path to oFono.
oFono should create a media transport and register it to PulseAudio
using the media end point path.
PulseAudio oFono BlueZ HF
| | | |
| | | connection |
| | | set-up |
| | |<............>|
| | NewConnection | |
| |<---------------| |
| SelectConfiguration | | |
|<--------------------| | |
| | | |
| SetConfiguration | | |
|<--------------------| | |
| | | |
Outgoing SCO connection - HFP <= 1.5
------------------------------------
When PulseAudio needs to setup the audio connection it will call media
transport acquire method. This will perform a SCO connection and return
the SCO socket file descriptor to PulseAudio.
PulseAudio oFono HF/AG
| | |
| transport acquire | |
|------------------------>| |
| | connect SCO |
| |..............>|
| return SCO fd | |
|<------------------------| |
| | |
Incoming SCO connection - HFP <= 1.5
------------------------------------
On an incoming SCO connection oFono will change to playing state. On
reception of this state change, PulseAudio will call media transport
acquire method to retrieve the SCO socket file descriptor.
PulseAudio oFono HF/AG
| | |
| | connect SCO |
| |<..............|
| state changed signal | |
|<------------------------| |
| | |
| transport acquire | |
|------------------------>| |
| | |
| return SCO fd | |
|<------------------------| |
| | |
Codec negotiation - HFP AG - HFP v1.6
-------------------------------------------
On reception of HF available codecs command (AT+BAC), the gateway may
start a codec selection procedure which will setup the correct media
transport. When a media transport already exists and it uses a different
codec, it should be closed before correct one is setup.
PulseAudio oFono HF
| | |
| | AT+BAC=u1,u2 |
| |<.............|
| | |
| | OK |
| |.............>|
| | |
| | +BCS:id |
| |.............>|
| | |
| | AT+BCS=id |
| |<.............|
| | |
| | OK |
| |.............>|
| configure Transport | |
|<--------------------| |
| | |
It may also be possible to force a codec selection from oFono.
PulseAudio oFono HF
| | |
| | +BCS:id |
| |............>|
| | |
| | AT+BCS=id |
| |<............|
| | |
| | OK |
| |............>|
| configure Transport | |
|<--------------------| |
| | |
Outgoing SCO connection - HFP AG - HFP v1.6
-------------------------------------------
Idem than for HFP v1.5
Incoming SCO connection - HFP AG - HFP v1.6
-------------------------------------------
It is pretty the same here as for outgoing SCO connection, except that
it is started upon reception of AT+BCC from the headset.
PulseAudio oFono HF
| | |
| | AT+BCC |
| |<............|
| | |
| | OK |
| |............>|
| | |
| | connect SCO |
| |............>|
| state changed signal | |
|<---------------------| |
| | |
| transport acquire | |
|--------------------->| |
| | |
| return SCO fd | |
|<---------------------| |
Codec negotiation - HFP HF - HFP v1.6
-------------------------------------------
Codec selection procedure started by gateway will end up by codec
property update and setup of the correct media transport.
When a media transport already exists and it uses a different codec, it
should be closed before correct one is setup.
PulseAudio oFono AG
| | |
| | +BCS:id |
| |<.............|
| | |
| | AT+BCS=id |
| |.............>|
| | |
| | OK |
| |<.............|
| configure Transport | |
|<--------------------| |
| | |
Outgoing SCO connection - HFP HF - HFP v1.6
-------------------------------------------
On media transport acquire, oFono requests connection from the gateway.
Then incoming SCO socket file descriptor will be returned to PulseAudio.
PulseAudio oFono AG
| | |
| transport acquire | |
|----------------------->| |
| | AT+BCC |
| |............>|
| | |
| | OK |
| |<............|
| | |
| | connect SCO |
| |<............|
| return SCO fd | |
|<-----------------------| |
| | |
Incoming SCO connection - HFP HF - HFP v1.6
-------------------------------------------
Idem than for HFP v1.5
AT+NREC - HFP AG
----------------
Reception of AT+NREC will update the NREC property of media transport interface
(listened by PulseAudio).
HF oFono PulseAudio
| AT+NREC | |
|............>| |
| | property |
| | changed signal |
| |--------------->|
| OK | |
|<............| |
| | |
+BSIR - HFP AG
--------------
PulseAudio can change in-band ring tone by calling SetProperty method of media
transport interface, which will send the proper +BSIR unsolicited event.
HF oFono PulseAudio app
| | | |
| | |<------------|
| | SetProperty | |
| |<---------------| |
| +BSIR:x | | |
|<............| | |
| | property | |
| | changed signal | |
| |--------------->| |
| | | |
AT+VGS,AT+VGM - HFP AG
----------------------
Reception of volume management command will update the corresponding volume
property of media transport interface (listened by PulseAudio).
HF oFono PulseAudio app
| | | |
| AT+VGS=xx | | |
|............>| | |
| | property | |
| | changed signal | |
| |--------------->| |
| OK | | |
|<............| |------------>|
| | | |
+VGS,+VGM - HFP AG
------------------
PulseAudio can change volume by calling SetProperty method of media transport
interface. This which will send the proper +VGx unsolicited event.
HF oFono PulseAudio app
| | | |
| | |<------------|
| | SetProperty | |
| |<---------------| |
| +VGS:xx | | |
|<............| property | |
| | changed signal | |
| |--------------->| |
| | |------------>|
| | | |