Samsung DVD-R155 Service Manual page 112

Circuit Operating Descriptions
ˇ ˇ Block Diagram of SAA7138
Though SAA7138 have multiplexer function for several input source,
but muliplexer of switching operation is done by other IC- HA118827 AV multiplexer.
And asloAudio ADC function of SAA7138 is not used.
but use built-in Audio ADC in S5L3210 MPEG CODEC.
Fig. 13-9
13-12 Samsung Electronics