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6.2.1.2 DAC Operation
The digital-to-analog conversion (DAC) simply reverses the procedure of the ADC. The digital
audio data stream is received by the DAC and the quantized values are decoded at the sampling
rate (Figure 6-3A) into DC levels, resulting in a descrete level wave form (Figure 6-3B). A filter
provides the final shaping of the wave (Figure 6-3C) before it is applied to the analog output
circuitry.
Quantized
Values
S0 S1 S2 S3 S4 S5 S6 S7 S8 S9 S10
A. Quantized Value Decoding
Figure 6–3. DAC Operation
Compressed sound formats provide efficient use of space by concentrating sampling/quantizing
in the middle of the sound spectrum and is suited for voice capture/playback. The DAC of the
ES1868 controller supports two type of compressed sound; ADPCM and ESPCM. The ADPCM
compressed format is compatible with common industry sound subsystems while ESPCM is a
proprietary format that offers greater performance.
C. Final Analog Output
Compaq Deskpro 4000 and 6000 Personal Computers
featuring the Pentium II Processor
First Edition - October 1997
Technical Reference Guide
B. Descrete Level Waveform
6-5
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