CSR8615A04-IQQF-R View Datasheet(PDF) - Unspecified
Part Name
Description
MFG CO.
'CSR8615A04-IQQF-R' PDF : 114 Pages View PDF
16.2.7 Automatic Gain Control
The AGC block attempts to:
â– Normalise the amplitude of the incoming audio signal to a desired range to increase perceived loudness
â– Reduce distortion due to clipping
â– Reduce amplitude variance observed from different users, phones and networks
Maintaining a consistent long-term loudness for the speech ensures it is more easily heard by the listener and it also
provides the subsequent processing block a larger amplitude signal to process. The behaviour of the AGC differs
from a dynamic range audio compressor. The convergence time for the AGC is much slower to reduce the non-
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The Frequency Emphasis feature can be used with any standard narrow band call, when the DAC is operating at a
sample rate of 8kHz. To complement the AEQ, High Frequency Emphasis can be added to improve the intelligibility
of the far end caller. The emphasis feature repairs frequencies (3469Hz to 4000Hz) that were lost due to the filters
of the cellular network and Bluetooth link. Information contained in the original speech from 281Hz to 3469Hz is used
to reconstruct the lost high frequency content.
The Frequency Expansion feature can be used with any standard narrow band call, but a special mode is invoked
when the DAC operate at a sample rate of 16kHz. The frequency expansion allows users to add in frequencies far
beyond the band limits caused by the cellular network and Bluetooth link. These expansion frequencies are added
between 3469Hz and 6156Hz. As in frequency emphasis, it uses the information contained in the original speech
from 281Hz to 3469Hz to reconstruct the lost high frequency content.
Pre-production Information
© Cambridge Silicon Radio Limited 2013
Confidential Information - This Material is Subject to CSR's Non-disclosure Agreement
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