SBC vs mSBC: Understanding Bluetooth Audio Codec Differences

This article explores the differences between the SBC and mSBC Bluetooth codecs, commonly used in various Bluetooth profiles.

Introduction

Bluetooth is a widely used short-range wireless technology operating in the 2.4 GHz ISM band, offering a range of approximately 10 to 100 meters. There are different Bluetooth versions, including Bluetooth Classic, Bluetooth Low Energy (BLE), and Bluetooth High Speed. Bluetooth supports various profiles based on their application.

Common profiles include:

• Hands-Free Profile (HFP)
• Headset Profile (HSP)
• A2DP (Advanced Audio Distribution Profile)
• A/V Remote Control Profile (AVRCP)
• Phone Book Access Profile (PBAP)
• Message Access Profile (MAP)

These profiles often leverage different audio codecs like aptX, SBC, mSBC, and Advanced Audio Coding (AAC).

SBC Audio Codec

SBC, or Sub Band Coding, is a crucial Bluetooth audio codec with the following features:

• Definition: Short for Sub Band Coding.
• Audio Quality: Provides reasonably good audio quality at medium bit rates while maintaining low computational complexity.
• Mandatory Codec: It’s the only mandatory codec used in the A2DP profile as specified by the Bluetooth SIG.
• Function: Acts as both a digital audio encoder and decoder.
• Usage: Transfers data to Bluetooth audio output devices such as headphones and speakers.
• Stream Support: SBC supports both mono and stereo streams.
• Sampling Frequencies: Supports sampling frequencies up to 48 kHz.
• Bit Rates: Supports bit rates up to 198 Kbps (mono stream) and up to 345 Kbps (stereo stream).
• Sub Bands: Uses either 4 or 8 sub-bands. Employs an adaptive bit allocation algorithm along with adaptive block PCM quantizers.
• A2DP Version: Used by A2DP profile version 1.3.

mSBC Audio Codec

mSBC, or modified SBC, is another important Bluetooth audio codec with these characteristics:

• Definition: It is a 16KHz monaural configuration of the SBC codec.
• HFP Version: Used by Hands-Free Profile v1.6.
• Also Known As: It is also known as WBS (Wide Band Speech).
• HD Voice Support: Developed to support mobile networks with HD voice.