Analog Devices ADAU1381 User Manual

One Technology Way • P.O. Box 9106 • Norwood, MA 02062-9106, U.S.A. • Tel: 781.329.4700 • Fax: 781.461.3113 • www.analog.com

INTRODUCTION

This user guide explains the signal flow and parameter settings
for the ADAU1381 sound engine. The ADAU1381 is ideal for
low power portable applications, such as digital camera audio.
During the recording or playing back of audio, the sound
engine provides many signal processing features to improve
audio quality.

DIGITAL CAMERA SYSTEM OVERVIEW

Although the ADAU1381 is flexible enough to be used in
several types of portable audio applications, its design specifically
targets digital camera systems. The sound processing engine
was, therefore, designed especially with such a system in mind.
In general, digital cameras use audio processing when recording
or playing back video. When recording, one or more microphones
mounted in the camera or connected externally capture the
audio data, which is then stored in the memory along with the
video data. During playback or review mode, the audio data is
retrieved from memory and played back through a speaker
mounted in the camera or through a jack for headphones or
other external connections.
In record mode, the source is an audio transducer (microphone)
and the target is memory. In playback mode, the source is
memory and the target is an audio transducer (speaker). In
both modes, the sound engine is positioned between the source
and target, processing the signal to improve audio quality.
Because the required audio processing differs depending on the
operating mode of the camera, several audio processing modes
have been implemented in the sound engine of the ADAU1381.
AUDIO MODE
RECORD
INPUT
PLAYBACK
INPUT
Please see the last page for an important warning and disclaimers.
Using the ADAU1381 Sound Engine

SOUND ENGINE SIGNAL FLOW BLOCK DIAGRAM

ENHANCED
WIND NOISE
STEREO
REDUCTION
CAPTURE
Evaluation Board User Guide

AUDIO PROCESSING MODES

Record Mode
Record mode takes audio input from a microphone. Wind noise
reduction is applied to remove unwanted noise from the signal
and improve audio clarity. The enhanced stereo capture algorithm
provides improved stereo separation when microphones are
spaced close together. The six-band equalizer can be programmed
to augment bands of interest and filter out unwanted frequencies.
The dual-band dynamics processor acts as an automatic level
control, compensating for fluctuating input signal levels. The
processed signal is output to a digital storage medium.
Two record modes exist: Record A (REC A) and Record B (REC B).
The only differences between the two modes are the six-band
equalizer and the dual-band dynamics processor settings. The
two record modes allow for different audio recording profiles,
such as voice or music. The recording profile can be changed by
a single write to the RAM parameter.
Playback Mode
Playback mode takes audio input from the digital storage. The six-
band equalizer is used for frequency compensation with the output
speaker or headphones. The dual-band dynamics processor acts
as a compressor, allowing for suitable playback levels even in
noisy environments. The playback output includes a digital
volume control for output level adjustment.
SIX-BAND
EQUALIZER
Figure 1.
Rev. 0 | Page 1 of 40
DUAL-BAND
DYNAMIC
PROCESSOR
UG-030
RECORD
OUTPUT
PLAYBACK
OUTPUT