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Bluetooth: Basic Audio Profile

This document describes how to run Basic Audio Profile functionality which includes:

  • Capabilities and Endpoint discovery

  • Audio Stream Endpoint procedures

Commands

bap --help
Subcommands:
   init
   select_broadcast       : <stream>
   create_broadcast       : [preset <preset_name>] [enc <broadcast_code>]
   start_broadcast        :
   stop_broadcast         :
   delete_broadcast       :
   create_broadcast_sink  : 0x<broadcast_id>
   sync_broadcast         : 0x<bis_index> [[[0x<bis_index>] 0x<bis_index>] ...]
                           [bcode <broadcast code> || bcode_str <broadcast code
                           as string>]
   stop_broadcast_sink    : Stops broadcast sink
   term_broadcast_sink    :
   discover               : [dir: sink, source]
   config                 : <direction: sink, source> <index> [loc <loc_bits>]
                           [preset <preset_name>]
   stream_qos             : interval [framing] [latency] [pd] [sdu] [phy] [rtn]
   qos                    : Send QoS configure for Unicast Group
   enable                 : [context]
   connect                : Connect the CIS of the stream
   stop
   list
   print_ase_info         : Print ASE info for default connection
   metadata               : [context]
   start
   disable
   release
   select_unicast         : <stream>
   preset                 : <sink, source, broadcast> [preset]
                           [config
                                 [freq <frequency>]
                                 [dur <duration>]
                                 [chan_alloc <location>]
                                 [frame_len <frame length>]
                                 [frame_blks <frame blocks>]]
                           [meta
                                 [pref_ctx <context>]
                                 [stream_ctx <context>]
                                 [program_info <program info>]
                                 [lang <ISO 639-3 lang>]
                                 [ccid_list <ccids>]
                                 [parental_rating <rating>]
                                 [program_info_uri <URI>]
                                 [audio_active_state <state>]
                                 [bcast_flag]
                                 [extended <meta>]
                                 [vendor <meta>]]
   send                   : Send to Audio Stream [data]
   bap_stats              : Sets or gets the statistics reporting interval in # of
                           packets
   set_location           : <direction: sink, source> <location bitmask>
   set_context            : <direction: sink, source><context bitmask> <type:
                           supported, available>
State Machine Transitions

Command

Depends

Allowed States

Next States

init

none

any

none

discover

init

any

any

config

discover

idle/codec-configured/qos-configured

codec-configured

qos

config

codec-configured/qos-configured

qos-configured

enable

qos

qos-configured

enabling

connect

qos/enable

qos-configured/enabling

qos-configured/enabling

[start]

enable/connect

enabling

streaming

disable

enable

enabling/streaming

disabling

[stop]

disable

disabling

qos-configure/idle

release

config

any

releasing/codec-configure/idle

list

none

any

none

select_unicast

none

any

none

send

enable

streaming

none

Example Central

Connect and establish a sink stream:

uart:~$ bt init
uart:~$ bap init
uart:~$ bt connect <address>
uart:~$ gatt exchange-mtu
uart:~$ bap discover sink
uart:~$ bap config sink 0
uart:~$ bap qos
uart:~$ bap enable
uart:~$ bap connect

Connect and establish a source stream:

uart:~$ bt init
uart:~$ bap init
uart:~$ bt connect <address>
uart:~$ gatt exchange-mtu
uart:~$ bap discover source
uart:~$ bap config source 0
uart:~$ bap qos
uart:~$ bap enable
uart:~$ bap connect
uart:~$ bap start

Disconnect and release:

uart:~$ bap disable
uart:~$ bap release

Example Peripheral

Listen:

uart:~$ bt init
uart:~$ bap init
uart:~$ bt advertise on

Server initiated disable and release:

uart:~$ bap disable
uart:~$ bap release

Example Broadcast Source

Create and establish a broadcast source stream:

uart:~$ bap init
uart:~$ bap create_broadcast
uart:~$ bap start_broadcast

Stop and release a broadcast source stream:

uart:~$ bap stop_broadcast
uart:~$ bap delete_broadcast

Example Broadcast Sink

Scan for and establish a broadcast sink stream. The command bap create_broadcast_sink will either use existing periodic advertising sync (if exist) or start scanning and sync to the periodic advertising with the provided broadcast ID before syncing to the BIG.

uart:~$ bap init
uart:~$ bap create_broadcast_sink 0xEF6716
No PA sync available, starting scanning for broadcast_id
Found broadcaster with ID 0xEF6716 and addr 03:47:95:75:C0:08 (random) and sid 0x00
Attempting to PA sync to the broadcaster
PA synced to broadcast with broadcast ID 0xEF6716
Attempting to sync to the BIG
Received BASE from sink 0x20019080:
Presentation delay: 40000
Subgroup count: 1
Subgroup 0x20024182:
   Codec Format: 0x06
   Company ID  : 0x0000
   Vendor ID   : 0x0000
   codec cfg id 0x06 cid 0x0000 vid 0x0000 count 16
      Codec specific configuration:
      Sampling frequency: 16000 Hz (3)
      Frame duration: 10000 us (1)
      Channel allocation:
               Front left (0x00000001)
               Front right (0x00000002)
      Octets per codec frame: 40
      Codec specific metadata:
      Streaming audio contexts:
         Unspecified (0x0001)
      BIS index: 0x01
         codec cfg id 0x06 cid 0x0000 vid 0x0000 count 6
         Codec specific configuration:
            Channel allocation:
               Front left (0x00000001)
         Codec specific metadata:
            None
      BIS index: 0x02
         codec cfg id 0x06 cid 0x0000 vid 0x0000 count 6
         Codec specific configuration:
            Channel allocation:
               Front right (0x00000002)
         Codec specific metadata:
            None
Possible indexes: 0x01 0x02
Sink 0x20019110 is ready to sync without encryption
uart:~$ bap sync_broadcast 0x01

Syncing to encrypted broadcast

If the broadcast is encrypted, the broadcast code can be entered with the bap sync_broadcast command as such:

Sink 0x20019110 is ready to sync with encryption
uart:~$ bap sync_broadcast 0x01 bcode 0102030405060708090a0b0c0d0e0f

The broadcast code can be 1-16 values, either as a string or a hexadecimal value.

Sink 0x20019110 is ready to sync with encryption
uart:~$ bap sync_broadcast 0x01 bcode_str thisismycode

Stop and release a broadcast sink stream:

uart:~$ bap stop_broadcast_sink
uart:~$ bap term_broadcast_sink

Init

The init command register local PAC records which are necessary to be able to configure stream and properly manage capabilities in use.

State Machine Transitions

Depends

Allowed States

Next States

none

any

none

uart:~$ bap init

Discover PAC(s) and ASE(s)

Once connected the discover command discover PAC records and ASE characteristics representing remote endpoints.

State Machine Transitions

Depends

Allowed States

Next States

init

any

any

Note

Use command gatt exchange-mtu to make sure the MTU is configured properly.

uart:~$ gatt exchange-mtu
Exchange pending
Exchange successful
uart:~$ bap discover [type: sink, source]
uart:~$ bap discover sink
conn 0x2000b168: codec_cap 0x2001f8ec dir 0x02
codec cap id 0x06 cid 0x0000 vid 0x0000
   Codec specific capabilities:
      Supported sampling frequencies:
         8000 Hz (0x0001)
         11025 Hz (0x0002)
         16000 Hz (0x0004)
         22050 Hz (0x0008)
         24000 Hz (0x0010)
         32000 Hz (0x0020)
         44100 Hz (0x0040)
         48000 Hz (0x0080)
         88200 Hz (0x0100)
         96000 Hz (0x0200)
         176400 Hz (0x0400)
         192000 Hz (0x0800)
         384000 Hz (0x1000)
      Supported frame durations:
         10 ms (0x02)
      Supported channel counts:
         1 channel (0x01)
      Supported octets per codec frame counts:
         Min: 40
         Max: 120
      Supported max codec frames per SDU: 1
   Codec capabilities metadata:
      Preferred audio contexts:
         Converstation (0x0002)
         Media (0x0004)
ep 0x81754e0
ep 0x81755d4
Discover complete: err 0

Select preset

The preset command can be used to either print the default preset configuration or set a different one, it is worth noting that it doesn’t change any stream previously configured.

uart:~$ bap preset
preset - <sink, source, broadcast> [preset]
         [config
               [freq <frequency>]
               [dur <duration>]
               [chan_alloc <location>]
               [frame_len <frame length>]
               [frame_blks <frame blocks>]]
         [meta
               [pref_ctx <context>]
               [stream_ctx <context>]
               [program_info <program info>]
               [lang <ISO 639-3 lang>]
               [ccid_list <ccids>]
               [parental_rating <rating>]
               [program_info_uri <URI>]
               [audio_active_state <state>]
               [bcast_flag]
               [extended <meta>]
               [vendor <meta>]]
uart:~$ bap preset sink
16_2_1
codec cfg id 0x06 cid 0x0000 vid 0x0000 count 16
   Codec specific configuration:
      Sampling frequency: 16000 Hz (3)
      Frame duration: 10000 us (1)
      Channel allocation:
                  Front left (0x00000001)
                  Front right (0x00000002)
      Octets per codec frame: 40
   Codec specific metadata:
      Streaming audio contexts:
         Game (0x0008)
QoS: interval 10000 framing 0x00 phy 0x02 sdu 40 rtn 2 latency 10 pd 40000

uart:~$ bap preset sink 32_2_1
32_2_1
codec cfg id 0x06 cid 0x0000 vid 0x0000 count 16
   Codec specific configuration:
      Sampling frequency: 32000 Hz (6)
      Frame duration: 10000 us (1)
      Channel allocation:
                  Front left (0x00000001)
                  Front right (0x00000002)
      Octets per codec frame: 80
   Codec specific metadata:
      Streaming audio contexts:
         Game (0x0008)
   QoS: interval 10000 framing 0x00 phy 0x02 sdu 80 rtn 2 latency 10 pd 40000

Configure preset

The bap preset command can also be used to configure the preset used for the subsequent commands. It is possible to add or set (or reset) any value. To reset the preset, the command can simply be run without the config or meta parameter. The parameters are using the assigned numbers values.

uart:~$ bap preset sink 32_2_1
32_2_1
codec cfg id 0x06 cid 0x0000 vid 0x0000 count 16
data #0: type 0x01 value_len 1
00000000: 06                                               |.                |
data #1: type 0x02 value_len 1
00000000: 01                                               |.                |
data #2: type 0x03 value_len 4
00000000: 03 00 00 00                                      |....             |
data #3: type 0x04 value_len 2
00000000: 50 00                                            |P.               |
meta #0: type 0x02 value_len 2
00000000: 08 00                                            |..               |
QoS: interval 10000 framing 0x00 phy 0x02 sdu 80 rtn 2 latency 10 pd 40000

uart:~$ bap preset sink 32_2_1 config freq 10
32_2_1
codec cfg id 0x06 cid 0x0000 vid 0x0000 count 16
data #0: type 0x01 value_len 1
00000000: 0a                                               |.                |
data #1: type 0x02 value_len 1
00000000: 01                                               |.                |
data #2: type 0x03 value_len 4
00000000: 03 00 00 00                                      |....             |
data #3: type 0x04 value_len 2
00000000: 50 00                                            |P.               |
meta #0: type 0x02 value_len 2
00000000: 08 00                                            |..               |
QoS: interval 10000 framing 0x00 phy 0x02 sdu 80 rtn 2 latency 10 pd 40000

uart:~$ bap preset sink 32_2_1 config freq 10 meta lang "eng" stream_ctx 4
32_2_1
codec cfg id 0x06 cid 0x0000 vid 0x0000 count 16
data #0: type 0x01 value_len 1
00000000: 0a                                               |.                |
data #1: type 0x02 value_len 1
00000000: 01                                               |.                |
data #2: type 0x03 value_len 4
00000000: 03 00 00 00                                      |....             |
data #3: type 0x04 value_len 2
00000000: 50 00                                            |P.               |
meta #0: type 0x02 value_len 2
00000000: 04 00                                            |..               |
meta #1: type 0x04 value_len 3
00000000: 65 6e 67                                         |eng              |
QoS: interval 10000 framing 0x00 phy 0x02 sdu 80 rtn 2 latency 10 pd 40000

Configure Codec

The config command attempts to configure a stream for the given direction using a preset codec configuration which can either be passed directly or in case it is omitted the default preset is used.

State Machine Transitions

Depends

Allowed States

Next States

discover

idle/codec-configured/qos-configured

codec-configured

uart:~$ bap config <direction: sink, source> <index> [loc <loc_bits>] [preset <preset_name>]
uart:~$ bap config sink 0
Setting location to 0x00000000
ASE config: preset 16_2_1
stream 0x2000df70 config operation rsp_code 0 reason 0

Configure Stream QoS

The stream_qos Sets a new stream QoS.

uart:~$ bap stream_qos <interval> [framing] [latency] [pd] [sdu] [phy] [rtn]
uart:~$ bap stream_qos 10

Configure QoS

The qos command attempts to configure the stream QoS using the preset configuration, each individual QoS parameter can be set with use optional parameters.

State Machine Transitions

Depends

Allowed States

Next States

config

qos-configured/codec-configured

qos-configured

uart:~$ bap qos

Enable

The enable command attempts to enable the stream previously configured.

State Machine Transitions

Depends

Allowed States

Next States

qos

qos-configured

enabling

uart:~$ bap enable [context]
uart:~$ bap enable Media

Connect

The connect command attempts to connect the stream previously configured. Sink streams will have to be started by the unicast server, and source streams will have to be started by the unicast client.

State Machine Transitions

Depends

Allowed States

Next States

qos/enable

qos-configured/enabling

qos-configured/enabling

uart:~$ bap connect

Start

The start command is only necessary when starting a source stream.

State Machine Transitions

Depends

Allowed States

Next States

enable/connect

enabling

streaming

uart:~$ bap start

Disable

The disable command attempts to disable the stream previously enabled, if the remote peer accepts then the ISO disconnection procedure is also initiated.

State Machine Transitions

Depends

Allowed States

Next States

enable

enabling/streaming

disabling

uart:~$ bap disable

Stop

The stop command is only necessary when acting as a sink as it indicates to the source the stack is ready to stop receiving data.

State Machine Transitions

Depends

Allowed States

Next States

disable

disabling

qos-configure/idle

uart:~$ bap stop

Release

The release command releases the current stream and its configuration.

State Machine Transitions

Depends

Allowed States

Next States

config

any

releasing/codec-configure/idle

uart:~$ bap release

List

The list command list the available streams.

State Machine Transitions

Depends

Allowed States

Next States

none

any

none

uart:~$ bap list
*0: ase 0x01 dir 0x01 state 0x01

Select Unicast

The select_unicast command set a unicast stream as default.

State Machine Transitions

Depends

Allowed States

Next States

none

any

none

uart:~$ bap select <ase>
uart:~$ bap select 0x01
Default stream: 1

To select a broadcast stream:

uart:~$ bap select 0x01 broadcast
Default stream: 1 (broadcast)

Send

The send command sends data over BAP Stream.

State Machine Transitions

Depends

Allowed States

Next States

enable

streaming

none

uart:~$ bap send [count]
uart:~$ bap send
Audio sending...