Gregory Maxwell authored 13 years ago and Jean-Marc Valin committed 13 years ago

non-ascii characters from the source.

Got authorization from all copyright holders

di_max was counting the _number_ of code-points remaining, not the
 largest one that could be used.

Timothy B. Terriberry authored 14 years ago and Jean-Marc Valin committed 14 years ago

This tunes the entropy model for coarse energy introduced in commit
 c1c40a76.
It uses a constant set of parameters, tuned from about an hour and a
 half of randomly selected test data encoded for each frame size,
 prediction type (inter/intra), and band number.
These will be slightly sub-optimal for different frame sizes, but
 should be better than what we were using.

For inter, this saves an average of 2.8, 5.2, 7.1, and 6.7 bits/frame
 for frame sizes of 120, 240, 480, and 960, respectively.
For intra, this saves an average of 1.5, 3.0, 4.5, and 5.3 bits/frame
 (for the same frame sizes, respectively).

Timothy B. Terriberry authored 14 years ago and Jean-Marc Valin committed 14 years ago

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.

original ec_encode_bin()/ec_decode_bin() to optimize performance when ft is
a power of two.

(rounding towards zero).

wider range of values.

thus save a few divisions.

represented by the laplace encoder (would have a probability of zero due
to finite precision)

to make the code more C89-friendly.

especially now that we have a custom version of that code anyway. Moved
the test code to tests/

infinitete loop in Laplace decoding when the data is corrupted.

me what I expect