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Wide Band Speech Link

BCM4354 Data Sheet

BROADCOM CONFIDENTIAL

Broadcom®

October 15, 2014 • 4354-DS109-R

Page 62

Wide Band Speech Link

In this case, the stereo FM audio is downsampled to 16 kHz and a mono or stereo stream is then sent through

the Bluetooth wideband speech link to a remote Bluetooth device, typically a headset. Two Bluetooth voice

connections must be used to transport stereo.

A2DP

In this case, the stereo FM audio is encoded by the on-chip SBC encoder and transported as an A2DP link to a

remote Bluetooth device. Sampling rates of 48 kHz, 44.1 kHz, and 32 kHz joint stereo are supported. An A2DP

“lite” stack is implemented in the BCM4354 to support this use case, which eliminates the need to route the SBC-

encoded audio back to the host to create the A2DP packets.

Autotune and Search Algorithms

The BCM4354 supports a number of FM search and tune functions that allows the host to implement many

convenient user functions, which are accessed through the Broadcom FM stack.

• Tune to Play: Allows the FM receiver to be programmed to a specific frequency.

• Search for SNR > Threshold: Checks the power level of the available channel and the estimated SNR of

the channel to help achieve precise control of the expected sound quality for the selected FM channel.

Specifically, the host can adjust its SNR requirements to retrieve a signal with a specific sound quality, or

adjust this to return the weakest channels.

• Alternate Frequency Jump: Allows the FM receiver to automatically jump to an alternate FM channel that

carries the same information, but has a better SNR. For example, when traveling, a user may pass through

a region where a number of channels carry the same station. When the user passes from one area to the

next, the FM receiver can automatically switch to another channel with a stronger signal to spare the user

from having to manually change the channel to continue listening to the same station.

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