Technical Reference Guide

5.8.4 AUDIO CODEC

The audio codec provides pulse code modulation (PCM) coding and decoding of audio information as well as the selection and/or mixing of analog channels. As shown in Figure 5-12, analog audio from a microphone, tape, or CD can be selected and, if to be recorded (saved) onto a disk drive, routed through an analog-to-digital converter (ADC). The resulting left and right PCM record data are muxed into a time-division-multiplexed (TDM) data stream (SD IN signal) that is routed to the audio controller. Playback (PB) audio takes the reverse path from the audio controller to the audio codec as SD OUT data and is decoded and processed by the digital-to- analog converter (DAC). The codec supports simultaneous record and playback of stereo (left and right) audio. The Sample Rate Generator may be set for sampling frequencies up to 48 KHz.

Analog audio may then be routed through 3D stereo enhancement processor or bypassed to the output selector (SEL). The integrated analog mixer provides the computer control-console functionality handling multiple audio inputs.

The D315 and D325 models use the Analog Devices AD1885 and the AD1981B respectively. These devices differ in that the AD1885 includes a 3D analog processor while the AD1981B includes an equalizer as well as SPDIF support.

Mic In

Line In (L)

S

Left

 

e

 

Audio

Rec

 

 

 

Audio

Format

Rec

Data (L)

Line In (R)

CD In (L) CD In (R)

l

 

 

Gain

e

 

 

c

Right

 

t

Audio

Rec

o

 

 

Gain

r

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

ADC

ADC

Rec Data (R)

Σ/Mixer

Sample

Rate

Gen.

 

SPDIF

 

 

 

3D Proc.

Analog

(L)

S

 

 

E

Output

(R)

L

Circuits

 

3D Proc.

AD1885 only

AD1981B only

(L)SW

(L)

PB

Gain

 

(R)

PB

Gain

(R)

 

DAC

DAC

PB Data (L)

EQ

PB Data (R)

EQ

AC97

Link

I/F

SD IN

SD Out

Audio Controller

Figure 5-12.Audio Codec Functional Block Diagram and Difference Matrix

5.8.5 AUDIO PROGRAMMING

Compaq D315 and hp d325 Personal Computers5-29

Featuring the AMD Athlon XP Processor

Second Edition - April 2003

Page 111
Image 111
HP D315 manual Audio Codec, Audio Programming