[BlueZ,14/14] bap: Create streams for required BISes

Commit Message

Iulia Tanasescu Aug. 21, 2024, 2:56 p.m. UTC

If a BAP Broadcast Sink is acting as a Scan Delegator and it has performed
short-lived PA sync with a Broadcaster added by a Broadcast Assistant, the
BASE should be parsed and streams need to be created only for BISes
requested by the Assistant.

This adds a BASS check inside parse_base, to filter out BISes that do not
require streams.

The bluetoothctl log below shows a Scan Delegator registering a Broadcast
Sink PAC and connecting to a Broadcast Assistant:

client/bluetoothctl
[bluetooth]# endpoint.register 00001851-0000-1000-8000-00805f9b34fb 0x06
[/local/endpoint/ep0] Auto Accept (yes/no): y
[/local/endpoint/ep0] Max Transports (auto/value): a
[/local/endpoint/ep0] Locations: 3
[/local/endpoint/ep0] Supported Context (value): 1
[bluetooth]# Endpoint /local/endpoint/ep0 registered
[bluetooth]# advertise on
[bluetooth]# [NEW] Device 00:60:37:31:7E:3F 00-60-37-31-7E-3F

The btmon log shows the Scan Delegator receiving the Add Source command
from a Broadcast Assistant, requesting to sync to BIS index 2 of the
provided Broadcaster. After PA sync, the BASE shows that the Broadcaster
is streaming 2 BISes, both matching the audio capabilities supported by
the Scan Delegator:

> ACL Data RX: Handle 0 flags 0x01 dlen 1
      ATT: Write Command (0x52) len 23
        Handle: 0x0040 Type: Broadcast Audio Scan Control Point (0x2bc7)
          Data[21]: 02014605638ad50e004dda9b02ffff010200000000
            Opcode: Add Source (0x02)
            Source_Address_Type: 1
            Source_Address: 0E:D5:8A:63:05:46
            Source_Adv_SID: 0
            Broadcast_ID: 0x9bda4d
            PA_Sync_State: Synchronize to PA - PAST not available
            PA_Interval: 0xffff
            Num_Subgroups: 1
            Subgroup #0:
              BIS_Sync State: 0x00000002
> HCI Event: LE Meta Event (0x3e) plen 50
      LE Periodic Advertising Report (0x0f)
        Sync handle: 0
        TX power: 127 dbm (0x7f)
        RSSI: -60 dBm (0xc4)
        CTE Type: No Constant Tone Extension (0xff)
        Data status: Complete
        Data length: 0x2a
        Service Data: Basic Audio Announcement (0x1851)
          Presetation Delay: 40000
          Number of Subgroups: 1
            Subgroup #0:
            Number of BIS(s): 2
            Codec: LC3 (0x06)
            Codec Specific Configuration: #0: len 0x02 type 0x01
            Codec Specific Configuration: Sampling Frequency: 16 Khz
                                          (0x03)
            Codec Specific Configuration: #1: len 0x02 type 0x02
            Codec Specific Configuration: Frame Duration: 10 ms (0x01)
            Codec Specific Configuration: #2: len 0x03 type 0x04
            Codec Specific Configuration: Frame Length: 40 (0x0028)
            Codec Specific Configuration: #3: len 0x05 type 0x03
            Codec Specific Configuration: Location: 0x00000001
            Codec Specific Configuration: Location: Front Left
                                          (0x00000001)
              BIS #0:
              Index: 1
              BIS #1:
              Index: 2
              Codec Specific Configuration: #0: len 0x05 type 0x03
              Codec Specific Configuration: Location: 0x00000002
              Codec Specific Configuration: Location: Front Right
                                            (0x00000002)

Only one transport will be created, for BIS index 2, since it was
the only one requested in the Add Source command:

[00-60-37-31-7E-3F]# [NEW] Device 0E:D5:8A:63:05:46 0E-D5-8A-63-05-46
[00-60-37-31-7E-3F]# [NEW] Transport
    /org/bluez/hci0/dev_0E_D5_8A_63_05_46/bis2/fd0
---
 profiles/audio/bap.c | 9 +++++++++
 1 file changed, 9 insertions(+)

Patch

diff --git a/profiles/audio/bap.c b/profiles/audio/bap.c
index bf924932a..a6a9f5818 100644
--- a/profiles/audio/bap.c
+++ b/profiles/audio/bap.c
@@ -1226,6 +1226,15 @@  static bool parse_base(struct bap_data *bap_data, struct bt_iso_base *base,
 			bass_add_stream(bap_data->device, meta, merged_caps,
 						qos, idx, bis_index);
 
+			if (!bass_check_bis(bap_data->device, bis_index)) {
+				/* If this Broadcast Sink is acting as a Scan
+				 * Delegator, only attempt to create streams
+				 * for the BISes required by the peer Broadcast
+				 * Assistant.
+				 */
+				continue;
+			}
+
 			/* Check if this BIS matches any local PAC */
 			bt_bap_verify_bis(bap_data->bap, bis_index,
 					merged_caps, &matched_lpac);