Assistive Listening Knowledge Base
  • Specification

Basic Audio Profile, version 1.0.3

From https://assistivelisteningknowledgebase.org/evidence/bluetooth-sig-2026-bap/ · record checked 13 October 2026

  • Bluetooth SIG Generic Audio Working Group
  • Bluetooth SIG

Standards body (Bluetooth SIG, an industry association funded by its member companies, which owns the Auracast trademark)

Summary

The Bluetooth LE Audio profile that sets the codec settings every broadcast transmitter and receiver must support, and defines Presentation Delay.

Key findings

  • Section 9.1 requires encrypted access to the ASCS, PACS and BASS characteristics using keys with at least 128 bits of entropy from the specified secure methods. Sections 9.1.3 and 9.1.4 require Broadcast Sources to support LE Security Mode 3 Level 1, encrypting sources to support Level 2, and Broadcast Sinks to support Levels 1 and 2; Level 3 is optional. The broadcast security levels and the encryption of the assistant-to-receiver control connection are separate requirements.
  • Section 1 describes BAP as controlling audio streams over Bluetooth Low Energy for unicast and broadcast use. Sections 1.6 and 2.2.2 define Broadcast Source and Broadcast Sink roles; a source establishes groups of broadcast isochronous streams and advertises their configuration, while a sink discovers and receives the streams. A Broadcast Assistant discovers streams and transfers reception information and decryption codes to the receiving device's Scan Delegator.
  • Table 3.14 and section 3.7.2.1.1 give Broadcast_ID as a three-octet identifier that helps scanning devices find a BIG and remains unchanged for that BIG's lifetime. Sections 1.6 and 3.7.2.2 define BASE as the Broadcast Audio Source Endpoint announcement structure, with codec and other parameters at group, subgroup and BIS levels; each subgroup contains streams intended to be decoded and presented together.
  • Section 6.5 describes Broadcast_Codes as the information needed to decrypt encrypted broadcast streams. Section 7.1.1 defines Presentation_Delay for a Broadcast Sink or receiving Unicast Server from the SDU Synchronization Reference to the start of presentation. Sections 7.1 and 7.2 include device processing in Presentation_Delay and distinguish it from the actual transfer delay, Transport_Latency; for broadcast reception, total delay comprises Broadcast Source processing, transport latency and Broadcast Sink presentation delay.
  • Every broadcast receiver must decode LC3 at 16 kHz (32 kbps) and 24 kHz (48 kbps) with 10 ms frames, and every broadcast transmitter must be able to send the 16 kHz setting; all 48 kHz settings are optional. Transmitters are advised to include at least one stream at a mandatory setting.
  • Each mandatory setting has a low-latency form (2 retransmissions, 10 ms maximum transport latency) and a high-reliability form (4 retransmissions, 60 ms). The retransmission numbers are recommendations that the radio may change.
  • Every broadcast setting in the table lists a Presentation Delay of 40 ms, and a broadcast receiver must be able to play audio no later than 40 ms after the stream's timing reference.
  • Total system delay is the transmitter's own processing time plus the radio transport latency plus the receiver's Presentation Delay, which includes its decoding and processing. The transmitter's processing time is left to each product.
  • Transmitters should place separate programmes or alternative versions of one programme (languages, mixes, dialogue-enhanced audio) in separate subgroups so listeners can choose between them.
  • Table 6.4, footnote 4, makes the 40,000 microsecond Presentation Delay entry a Broadcast Sink capability requirement; it is not a fixed total system delay. Section 7.2 separately includes source processing, transport latency and Presentation Delay in total delay.
  • The Version History records Board adoption of version 1.0 on 14 September 2021, version 1.0.1 on 21 June 2022, version 1.0.2 on 1 October 2024 and version 1.0.3 on 23 June 2026. The abstract describes distribution and reception of audio over Bluetooth LE.
  • Section 1.4.1, Table 1.1, lists errata incorporated from version 1.0.1 to 1.0.2, including Broadcast_ID, Basic Audio Announcements and Broadcast Audio Stream configuration. It does not describe the changes from 1.0 to 1.0.1.
  • Section 1.4.2, Table 1.2, lists errata incorporated from version 1.0.2 to 1.0.3, including Broadcast Source audio capability configuration, Basic Audio Announcements, Broadcast Audio Stream configuration, and adding and modifying broadcast sources. The table identifies affected procedures rather than measured improvements.
  • Section 3.7.2.2 and Figure 3.1 illustrate one BIG containing four BISes in two subgroups: left and right Spanish audio in one, left and right English audio in the other. Subgroups and their metadata can supply user-interface choices. Sections 4.3.4.5-4.3.4.7 illustrate separate stereo and mono subgroup arrangements.
  • Tables 3.11 and 6.4 include 48 kHz LC3 configurations at 80 and 96 kbps with either 7.5 or 10 ms frames, plus 124.8 kbps with 7.5 ms frames and 124 kbps with 10 ms frames. These are per-channel codec rates; the 48 kHz configurations are optional for Broadcast Sinks.
  • Table 3.17 lists Broadcast Sink decoding support for 16 kHz/32 kbps and 24 kHz/48 kbps at 10 ms as mandatory, and their 7.5 ms counterparts as optional. Table 6.4 separates audio SDU sizes from retransmission settings; footnote 2 scales the SDU size by channel count and codec-frame blocks. The listed codec rates therefore exclude radio overhead and retransmissions.

Limits

Defines what devices must support, not how a venue system is set up or measured.

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Cite this source

Bluetooth SIG Generic Audio Working Group. Basic Audio Profile, version 1.0.3. Bluetooth SIG. 23 June 2026. https://www.bluetooth.com/wp-content/uploads/Files/Specification/HTML/bap_v1-0-3_1782503972/BAP_v1.0.3/out/en/index-en.html (accessed 13 October 2026).

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