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subband coding (SBC)

Subcarrier band coding is a technique used in audio compression and in a Bluetooth profile. As for audio compression, subband coding is used in MPEG, MP3, mp3Pro and ATRAC.

Subband coding works with masking and divides the frequency spectrum of the audio signal into frequency bands with different bandwidths. Usually there are 32 frequency bands, which can be variable quantized individually and independently. Important frequency bands have a higher bandwidth, unimportant ones a lower bandwidth, or are not considered at all in the compression. Thus, frequency bands with high audio content and high dynamics can be quantized with high sample depth, while others can be quantized with low sample depth.

The Subband Coding( SBC) used in Bluetooth is a coding method that was developed specifically for the Bluetooth Advanced Audio Distribution Profile( A2DP).

SBC compression in Bluetooth

SBC compression in Bluetooth

SBC compression generates bitstreams of 127 kbit/s to 345 kbit/s and places lower demands on the hardware than MP3, for example. The different bit rates result in different quality characteristics for mono and joint stereo.

SBC transmitters and receivers agree on a sampling frequency and bit rate before transmission. The transmitter derives the timestamp for the correct playback point from the sampling rate.

Englisch: subband coding - SBC
Updated at: 25.02.2018
#Words: 201
Links: coding, audio compression, Bluetooth profile, arsenic (As), moving picture experts group (MPEG)
Translations: DE

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