Compaq EN Series Technical Reference Manual page 148

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 discrete 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 efficiently use space by concentrating sampling/quantizing in the
middle of the sound spectrum and are suited for voice capture/playback. The DAC of the ES1869
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 EN Series of Personal Computers
Desktop and Minitower Form Factors
Third Edition–- September1998
Technical Reference Guide
B. Discrete Level Waveform
6-5