(a) Every person who commits a public offense, for which any specification of three time periods of imprisonment in any state prison or imprisonment pursuant to subdivision (h) of Section 1170 is now prescribed by law or for which only a single term of imprisonment in state prison or imprisonment pursuant to subdivision (h) of Section 1170 is specified shall, unless such convicted person be placed on probation, a new trial granted, or the imposing of sentence suspended, be sentenced pursuant to Chapter 4.5 (commencing with Section 1170) of Title 7 of Part 2.
(b) For any person not sentenced under such provision, but who is sentenced to be imprisoned in the state prison or imprisonment pursuant to subdivision (h) of Section 1170, including imprisonment not exceeding one year and one day, the court imposing the sentence shall not fix the term or duration of the period of imprisonment.