Philips CD-I - Page 56

1.5. Audio processing.
1.5.1 ADPCM decoding
CD-I audio data is decoded from ADPCM into 16 bit PCM.
The CD interface subsystem can also process the CD-I
audio data coming from system RAM memory to the ADPCM
decoding function. The kinds of CD-I audio data are:
o 8-bit ADPCM (level A)
o 4-bit ADPCM (level B)
o 4-bit ADPCM (level C)
1.5.2 Audio processing unit.
mono/stereo
mono/stereo
mono/stereo
The audio processing unit converts PCM audio data
coming from the ADPCM decoder to the analog audio
outputs. It can process PCM data from CD-DA tracks not
only on a CD-I disc but also on a CD-DA disc.
It supports audio mixing and attenuation in order to
control both the volume and balance for a stereo
signal, and both the volume and panning for 2 mono
signals.
The analog audio outputs are finally fed to 2
connectors (stereo left and right), and also to a
headphone jack with volume control on the front panel.
1.6. Interrupt.
Touching the Abort switch generates an interrupt. This
interrupt invokes a system function, which forces the
currently running program to stop.
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