In the Staden's 1995 paper the SCF file format specification provides
all four (for A, C, G, and T) not just the highest, quality measures for
each basecall in a read. What happened with this requirement since 1995?
Since the present standard quality measure is the phred score, what is a
way to get four phred scores for each basecall? Phred documentation is
silent about this. Any pointers would be appreciated.