Common Audio Profile

API Reference

group bt_cap

Common Audio Profile (CAP)

[Experimental] Users should note that the APIs can change as a part of ongoing development.

Enums

enum bt_cap_set_type

Type of CAP set.

Values:

enumerator BT_CAP_SET_TYPE_AD_HOC

The set is an ad-hoc set.

enumerator BT_CAP_SET_TYPE_CSIP

The set is a CSIP Coordinated Set.

Functions

int bt_cap_acceptor_register(const struct bt_csip_set_member_register_param *param, struct bt_csip_set_member_svc_inst **svc_inst)

Register the Common Audio Service.

This will register and enable the service and make it discoverable by clients. This will also register a Coordinated Set Identification Service instance.

This shall only be done as a server, and requires BT_CAP_ACCEPTOR_SET_MEMBER . If BT_CAP_ACCEPTOR_SET_MEMBER is not enabled, the Common Audio Service will by statically registered.

Parameters:

  • param – [in] Coordinated Set Identification Service register parameters.

  • svc_inst – [out] Pointer to the registered Coordinated Set Identification Service.

Returns:

0 if success, errno on failure.

int bt_cap_initiator_unicast_discover(struct bt_conn *conn)

Discovers audio support on a remote device.

This will discover the Common Audio Service (CAS) on the remote device, to verify if the remote device supports the Common Audio Profile.

Parameters:

  • conn – Connection to a remote server.

Returns:

0 on success or negative error value on failure.

void bt_cap_stream_ops_register(struct bt_cap_stream *stream, struct bt_bap_stream_ops *ops)

Register Audio operations for a Common Audio Profile stream.

Register Audio operations for a stream.

Parameters:

  • stream – Stream object.

  • ops – Stream operations structure.

int bt_cap_stream_send(struct bt_cap_stream *stream, struct net_buf *buf, uint16_t seq_num, uint32_t ts)

Send data to Common Audio Profile stream.

See bt_bap_stream_send() for more information

Note

Support for sending must be supported, determined by CONFIG_BT_AUDIO_TX .

Parameters:

  • stream – Stream object.

  • buf – Buffer containing data to be sent.

  • seq_num – Packet Sequence number. This value shall be incremented for each call to this function and at least once per SDU interval for a specific channel.

  • ts – Timestamp of the SDU in microseconds (us). This value can be used to transmit multiple SDUs in the same SDU interval in a CIG or BIG. Can be omitted by using BT_ISO_TIMESTAMP_NONE which will simply enqueue the ISO SDU in a FIFO manner.

Return values:
int bt_cap_stream_get_tx_sync(struct bt_cap_stream *stream, struct bt_iso_tx_info *info)

Get ISO transmission timing info for a Common Audio Profile stream.

See bt_bap_stream_get_tx_sync() for more information

Note

Support for sending must be supported, determined by CONFIG_BT_AUDIO_TX .

Parameters:

  • stream – [in] Stream object.

  • info – [out] Transmit info object.

Return values:
int bt_cap_initiator_register_cb(const struct bt_cap_initiator_cb *cb)

Register Common Audio Profile callbacks.

Parameters:

  • cb – The callback structure. Shall remain static.

Returns:

0 on success or negative error value on failure.

int bt_cap_initiator_unicast_audio_start(const struct bt_cap_unicast_audio_start_param *param, struct bt_bap_unicast_group *unicast_group)

Setup and start unicast audio streams for a set of devices.

The result of this operation is that the streams in param will be initialized and will be usable for streaming audio data. The unicast_group value can be used to update and stop the streams.

Note

CONFIG_BT_CAP_INITIATOR and CONFIG_BT_BAP_UNICAST_CLIENT must be enabled for this function to be enabled.

Parameters:

  • param – [in] Parameters to start the audio streams.

  • unicast_group – [out] Pointer to the unicast group.

Returns:

0 on success or negative error value on failure.

int bt_cap_initiator_unicast_audio_update(const struct bt_cap_unicast_audio_update_param params[], size_t count)

Update unicast audio streams.

This will update the metadata of one or more streams.

Note

CONFIG_BT_CAP_INITIATOR and CONFIG_BT_BAP_UNICAST_CLIENT must be enabled for this function to be enabled.

Parameters:

  • params – Array of update parameters.

  • count – The number of entries in params.

Returns:

0 on success or negative error value on failure.

int bt_cap_initiator_unicast_audio_stop(struct bt_bap_unicast_group *unicast_group)

Stop unicast audio streams for a unicast group.

Note

CONFIG_BT_CAP_INITIATOR and CONFIG_BT_BAP_UNICAST_CLIENT must be enabled for this function to be enabled.

Parameters:

  • unicast_group – The group of unicast devices to stop. The audio streams in this will be stopped and reset, and the unicast_group will be invalidated.

Returns:

0 on success or negative error value on failure.

int bt_cap_initiator_unicast_audio_cancel(void)

Cancel any current Common Audio Profile procedure.

This will stop the current procedure from continuing and making it possible to run a new Common Audio Profile procedure.

It is recommended to do this if any existing procedure take longer time than expected, which could indicate a missing response from the Common Audio Profile Acceptor.

This does not send any requests to any Common Audio Profile Acceptors involved with the current procedure, and thus notifications from the Common Audio Profile Acceptors may arrive after this has been called. It is thus recommended to either only use this if a procedure has stalled, or wait a short while before starting any new Common Audio Profile procedure after this has been called to avoid getting notifications from the cancelled procedure. The wait time depends on the connection interval, the number of devices in the previous procedure and the behavior of the Common Audio Profile Acceptors.

The respective callbacks of the procedure will be called as part of this with the connection pointer set to 0 and the err value set to -ECANCELED.

Return values:

  • 0 – on success

  • -EALREADY – if no procedure is active

int bt_cap_initiator_broadcast_audio_create(const struct bt_cap_initiator_broadcast_create_param *param, struct bt_cap_broadcast_source **broadcast_source)

Create a Common Audio Profile broadcast source.

Create a new audio broadcast source with one or more audio streams.

  • *

Note

CONFIG_BT_CAP_INITIATOR and CONFIG_BT_BAP_BROADCAST_SOURCE must be enabled for this function to be enabled.

Parameters:

  • param – [in] Parameters to start the audio streams.

  • broadcast_source – [out] Pointer to the broadcast source created.

Returns:

0 on success or negative error value on failure.

int bt_cap_initiator_broadcast_audio_start(struct bt_cap_broadcast_source *broadcast_source, struct bt_le_ext_adv *adv)

Start Common Audio Profile broadcast source.

The broadcast source will be visible for scanners once this has been called, and the device will advertise audio announcements.

This will allow the streams in the broadcast source to send audio by calling bt_bap_stream_send().

Note

CONFIG_BT_CAP_INITIATOR and CONFIG_BT_BAP_BROADCAST_SOURCE must be enabled for this function to be enabled.

Parameters:

  • broadcast_source – Pointer to the broadcast source.

  • adv – Pointer to an extended advertising set with periodic advertising configured.

Returns:

0 on success or negative error value on failure.

int bt_cap_initiator_broadcast_audio_update(struct bt_cap_broadcast_source *broadcast_source, const uint8_t meta[], size_t meta_len)

Update broadcast audio streams for a Common Audio Profile broadcast source.

Note

CONFIG_BT_CAP_INITIATOR and CONFIG_BT_BAP_BROADCAST_SOURCE must be enabled for this function to be enabled.

Parameters:

  • broadcast_source – The broadcast source to update.

  • meta – The new metadata. The metadata shall contain a list of CCIDs as well as a non-0 context bitfield.

  • meta_len – The length of meta.

Returns:

0 on success or negative error value on failure.

int bt_cap_initiator_broadcast_audio_stop(struct bt_cap_broadcast_source *broadcast_source)

Stop broadcast audio streams for a Common Audio Profile broadcast source.

Note

CONFIG_BT_CAP_INITIATOR and CONFIG_BT_BAP_BROADCAST_SOURCE must be enabled for this function to be enabled.

Parameters:

  • broadcast_source – The broadcast source to stop. The audio streams in this will be stopped and reset.

Returns:

0 on success or negative error value on failure.

int bt_cap_initiator_broadcast_audio_delete(struct bt_cap_broadcast_source *broadcast_source)
int bt_cap_initiator_broadcast_get_id(const struct bt_cap_broadcast_source *broadcast_source, uint32_t *const broadcast_id)

Get the broadcast ID of a Common Audio Profile broadcast source.

This will return the 3-octet broadcast ID that should be advertised in the extended advertising data with BT_UUID_BROADCAST_AUDIO_VAL as BT_DATA_SVC_DATA16.

See table 3.14 in the Basic Audio Profile v1.0.1 for the structure.

Parameters:

  • broadcast_source – [in] Pointer to the broadcast source.

  • broadcast_id – [out] Pointer to the 3-octet broadcast ID.

Returns:

int 0 if on success, errno on error.

int bt_cap_initiator_broadcast_get_base(struct bt_cap_broadcast_source *broadcast_source, struct net_buf_simple *base_buf)

Get the Broadcast Audio Stream Endpoint of a Common Audio Profile broadcast source.

This will encode the BASE of a broadcast source into a buffer, that can be used for advertisement. The encoded BASE will thus be encoded as little-endian. The BASE shall be put into the periodic advertising data (see bt_le_per_adv_set_data()).

See table 3.15 in the Basic Audio Profile v1.0.1 for the structure.

Parameters:

  • broadcast_source – Pointer to the broadcast source.

  • base_buf – Pointer to a buffer where the BASE will be inserted.

Returns:

int 0 if on success, errno on error.

int bt_cap_initiator_unicast_to_broadcast(const struct bt_cap_unicast_to_broadcast_param *param, struct bt_cap_broadcast_source **source)

Hands over the data streams in a unicast group to a broadcast source.

The streams in the unicast group will be stopped and the unicast group will be deleted. This can only be done for source streams.

Note

CONFIG_BT_CAP_INITIATOR , CONFIG_BT_BAP_UNICAST_CLIENT and CONFIG_BT_BAP_BROADCAST_SOURCE must be enabled for this function to be enabled.

Parameters:

  • param – The parameters for the handover.

  • source – The resulting broadcast source.

Returns:

0 on success or negative error value on failure.

int bt_cap_initiator_broadcast_to_unicast(const struct bt_cap_broadcast_to_unicast_param *param, struct bt_bap_unicast_group **unicast_group)

Hands over the data streams in a broadcast source to a unicast group.

The streams in the broadcast source will be stopped and the broadcast source will be deleted.

Note

CONFIG_BT_CAP_INITIATOR , CONFIG_BT_BAP_UNICAST_CLIENT and CONFIG_BT_BAP_BROADCAST_SOURCE must be enabled for this function to be enabled.

Parameters:

  • param – [in] The parameters for the handover.

  • unicast_group – [out] The resulting broadcast source.

Returns:

0 on success or negative error value on failure.

struct bt_cap_initiator_cb
#include <cap.h>

Callback structure for CAP procedures.

union bt_cap_set_member
#include <cap.h>

Represents a Common Audio Set member that are either in a Coordinated or ad-hoc set.

Public Members

struct bt_conn *member

Connection pointer if the type is BT_CAP_SET_TYPE_AD_HOC.

struct bt_csip_set_coordinator_csis_inst *csip

CSIP Coordinated Set struct used if type is BT_CAP_SET_TYPE_CSIP.

struct bt_cap_stream
#include <cap.h>
struct bt_cap_unicast_audio_start_stream_param
#include <cap.h>

Public Members

union bt_cap_set_member member

Coordinated or ad-hoc set member.

struct bt_cap_stream *stream

Stream for the member.

struct bt_bap_ep *ep

Endpoint reference for the stream.

struct bt_audio_codec_cfg *codec_cfg

Codec configuration.

The codec_cfg.meta shall include a list of CCIDs (BT_AUDIO_METADATA_TYPE_CCID_LIST) as well as a non-0 stream context (BT_AUDIO_METADATA_TYPE_STREAM_CONTEXT) bitfield.

struct bt_cap_unicast_audio_start_param
#include <cap.h>

Public Members

enum bt_cap_set_type type

The type of the set.

size_t count

The number of parameters in stream_params.

struct bt_cap_unicast_audio_start_stream_param *stream_params

Array of stream parameters.

struct bt_cap_unicast_audio_update_param
#include <cap.h>

Public Members

struct bt_cap_stream *stream

Stream for the member.

size_t meta_len

The length of meta.

uint8_t *meta

The new metadata.

The metadata shall a list of CCIDs as well as a non-0 context bitfield.

struct bt_cap_initiator_broadcast_stream_param
#include <cap.h>

Public Members

struct bt_cap_stream *stream

Audio stream.

size_t data_len

The length of the p data array.

The BIS specific data may be omitted and this set to 0.

uint8_t *data

BIS Codec Specific Configuration.

struct bt_cap_initiator_broadcast_subgroup_param
#include <cap.h>

Public Members

size_t stream_count

The number of parameters in stream_params.

struct bt_cap_initiator_broadcast_stream_param *stream_params

Array of stream parameters.

struct bt_audio_codec_cfg *codec_cfg

Subgroup Codec configuration.

struct bt_cap_initiator_broadcast_create_param
#include <cap.h>

Public Members

size_t subgroup_count

The number of parameters in subgroup_params.

struct bt_cap_initiator_broadcast_subgroup_param *subgroup_params

Array of stream parameters.

struct bt_audio_codec_qos *qos

Quality of Service configuration.

uint8_t packing

Broadcast Source packing mode.

BT_ISO_PACKING_SEQUENTIAL or BT_ISO_PACKING_INTERLEAVED.

Note

This is a recommendation to the controller, which the controller may ignore.

bool encryption

Whether or not to encrypt the streams.

uint8_t broadcast_code[BT_AUDIO_BROADCAST_CODE_SIZE]

16-octet broadcast code.

Only valid if encrypt is true.

If the value is a string or a the value is less than 16 octets, the remaining octets shall be 0.

Example: The string “Broadcast Code” shall be [42 72 6F 61 64 63 61 73 74 20 43 6F 64 65 00 00]

struct bt_cap_unicast_to_broadcast_param
#include <cap.h>

Public Members

struct bt_bap_unicast_group *unicast_group

The source unicast group with the streams.

bool encrypt

Whether or not to encrypt the streams.

If set to true, then the broadcast code in broadcast_code will be used to encrypt the streams.

uint8_t broadcast_code[BT_ISO_BROADCAST_CODE_SIZE]

16-octet broadcast code.

Only valid if encrypt is true.

If the value is a string or a the value is less than 16 octets, the remaining octets shall be 0.

Example: The string “Broadcast Code” shall be [42 72 6F 61 64 63 61 73 74 20 43 6F 64 65 00 00]

struct bt_cap_broadcast_to_unicast_param
#include <cap.h>

Public Members

struct bt_cap_broadcast_source *broadcast_source

The source broadcast source with the streams.

The broadcast source will be stopped and deleted.

enum bt_cap_set_type type

The type of the set.

size_t count

The number of set members in members.

This value shall match the number of streams in the broadcast_source.

union bt_cap_set_member **members

Coordinated or ad-hoc set members.