1. 26 Aug, 2010 2 commits
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  5. 12 Aug, 2010 2 commits
    • Timothy B. Terriberry's avatar
      Rework coarse energy coding. · c1c40a76
      Timothy B. Terriberry authored
      This changes how the PDF used to code coarse energy.
      New features:
      1) The probability of 0 (p0) is now indepedent of the decay rate
       of the remaining values; this additional flexibility will allow
       us to model the actual distribution better, though that
       improvement is not part of this patch.
      2) There is a guaranteed minimum number of encodable energy
          deltas.
         This ensures that even the most extreme sudden volume changes
          can be accurately represented.
      3) The tail end of the distribution has an adjustable (through a
          constant in the code) minimum probability.
         This allows us to lower the worst-case bit cost of a single
          delta.
      4) The codebook is interleaved as 0, -1, +1, -2, +2, ... instead
          of the 0, +1, -1, +2, -2, ... order used before (see 5).
      5) There is no restriction that p0 be even.
         Any remaining, unused part of the code is assigned to an
          additional negative value (collected inter data suggests that
          very large negative deltas are more common than very large
          positive ones).
         If the minimum probability is greater than 1, then an
          additional positive delta with a smaller probablity may also
          be added.
      6) Once the tail of the distribution is reached, the energy delta
          is computed directly, instead of continuing to loop through
          the codebook.
         This reduces the worst-case computational cost.
      c1c40a76
    • Jean-Marc Valin's avatar
      6ac26ecf
  6. 10 Aug, 2010 1 commit
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