16.2.12 Noise Dependent Volume Control
The NDVC block improves the intelligibility of the receive path signal by increasing the analogue DAC gain value
based on the send noise estimate from the send path noise suppression block. As the send noise estimate increases,
the NDVC algorithm increases the analogue DAC gain value. The NDVC uses hysteresis to minimise the artefacts
generated by rapidly adjusting the DAC gain due to the fluctuation in the environmental noise.
16.2.13 Fixed Gains
There are fixed gain controls at all inputs and outputs to the system so that levels are set according to hardware
constraints and industry standards.
16.2.14 Frequency Enhanced Speech Intelligibility
Frequency enhanced speech intelligibility on the CSR8640 BGA works with the adaptive equalisation module, see
Section 16.2.9, and the NDVC module, see Section 16.2.12, to enhance intelligibility in the presence of noise. This
combination of functions creates higher frequency information, which in the presence of noise, makes it much easier
for the listener to differentiate between consonant pairs, therefore improving intelligibility. This also reduces listener
fatigue as it requires less concentration effort from the user. This can lead to improved dual-tasking performance.
16.3
Music Enhancements
16.3.1
Audio Decoders
CSR8640 BGA supports:
■
A wide range of standard decoders:
■
SBC
■
MP3
■
AAC
■
Faststream codec:
■
Low-latency
■
No video/lip-sync issues while watching a video or playing games
■
Jitter handling and high quality sample rate matching
■
Low power consumption
Advance Information
This material is subject to CSR's non-disclosure agreement
© Cambridge Silicon Radio Limited 2011
Page 99 of 110
CS-209182-DSP1
CSR8640 BGA
Data Sheet
