making this assumption decoding of the second bit can already start before the first bit has been decoded completely thus when the first bit indeed turns out to have the mps value the second bit is also available and can be sent to the output as well when the first bit turns out to have the lps value the results of the second branch are simply discarded the flow diagram will now be described in a little more detail the u201c read p 1 and p 2 u201d block of fig4 retrieves the probabilities values p 1 and p 2 the probability pi is just the normal value that is always used for decoding a single bit and is the probability that the first symbol to be decoded has the lps value the probability p 2 is the probability that the second symbol to be decoded has the lps value assuming that the first symbol to be decoded has the mps value an external model produces the second probability p 2 in the normal way but looks one step ahead by filling in the mps value for the unknown first bit the left branch now proceeds in a usual manner as described in wo 99 49579 phn 16 822 the right branch skips over the decoding of the first.