In a DVD reader, does a ...SA expressed in RLBN (e.g., in
VTS_VOBU_ADMAP) ever reference a location in the data stream after the
stream is peeled off the disk or do such start addresses always
ultimately map to physical sectors.  Put another way: Is the stream
upstream of the track buffer sequential other than interleaved blocks
that are selectively ignored or output depending on their header data
like audio subchannels and rearrangement of I, P, and B frames
attending decompression).