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Makes celt_exp2() use Q10 input to avoid problems on very low energy.
Also makes the pitch downsampling more conservative on gain to avoid
problems later.

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

Use a closed-form formula for the search instead.
This requires an integer sqrt, so it is not actually closed-form,
 but the number of iterations is O(qb) instead of O(2**qb).

Timothy B. Terriberry authored 15 years ago and Jean-Marc Valin committed 15 years ago

Update the log2 approximation to accomodate the increased bit precision from bd0610d2. This requires another term in the power series to reduce the error to the level of truncation (peak absolute error 0.621785). Also refactor the rounding bias term so that further changes to DB_SHIFT will leave the result unbiased.

Timothy Terriberry authored 15 years ago and Jean-Marc Valin committed 15 years ago

Expose the normalized range for reciprocal square roots in fixed-point mode. This allows subsequnt calculations to use the full precision of the result.

Timothy B. Terriberry authored 15 years ago and Jean-Marc Valin committed 15 years ago

Accuracy for rsqrt, rcp, cos, and log2 is now at the level of truncation error
 for the current output resolution of these functions.
sqrt and exp2 still have non-trivial algebraic error, but this cannot be
 reduced much further using the current method without additional computation.
Also updates the fast float approximations for log2 and exp2 with coefficients
 that give slightly lower maximum relative error.

Patch modified by Jean-Marc Valin to leave the cos approximation as is and
leave the check for x<-15 in exp2 as is.

by POSIX. The other _t types that are not part of the API are still there
for now. Also, got rid of all that was left of the 64-bit types.

intra energy for low bitrates, and a bit of very high bitrate tuning

directly instead of converting to dB and later dividing by 6.

commit ea807b68678dd76175def2c5eb006c6bdb16679e
Author: Jean-Marc Valin <jean-marc.valin@usherbrooke.ca>
Date:   Wed Mar 25 23:24:41 2009 -0400

    cleanup before merge

commit 73ad1a0202641be6a23903e464ece21fe332a131
Author: Jean-Marc Valin <jean-marc.valin@usherbrooke.ca>
Date:   Sat Mar 21 00:02:16 2009 -0400

    Some tuning of the new stereo

commit c05057eb57a7723045214a2f830fd561388ae48a
Author: Jean-Marc Valin <jean-marc.valin@usherbrooke.ca>
Date:   Sun Mar 15 19:56:11 2009 -0400

    fixed-point: atan2() converted

commit a8476cf8be55b0612d42df98d9807ca1335adfe3
Author: Jean-Marc Valin <jean-marc.valin@usherbrooke.ca>
Date:   Sat Mar 14 23:10:04 2009 -0400

    fixed-point: Getting the new stereo code working in fixed-point (still more
    work left)

commit 70a452761a5ce15700664e7167886dce5914cbd0
Author: Jean-Marc Valin <jean-marc.valin@usherbrooke.ca>
Date:   Mon Mar 2 23:36:25 2009 -0500

    Coding left and right independently for lower bands

commit 4efd1e6385c7d036749080265a8d26668312b91b
Author: Jean-Marc Valin <jean-marc.valin@usherbrooke.ca>
Date:   Sun Mar 1 23:56:46 2009 -0500

    Removed the sqrt(C) from the normalisation, which simplifies a lot of things.

commit a4f3c5c60bc396bf644afa49b49e6b24ccf144f8
Author: Jean-Marc Valin <jean-marc.valin@usherbrooke.ca>
Date:   Fri Feb 20 20:49:38 2009 -0500

    Better point stereo calculation when we don't encode the side anyway

commit f08525de4739f4017d19ec2e2022883deda8f826
Author: Jean-Marc Valin <jean-marc.valin@usherbrooke.ca>
Date:   Thu Feb 19 19:43:09 2009 -0500

    Apparently, Timothy's calculations for fine energy allocation also apply
    to the quantisation of theta.

commit 6548cffc9d3f996b8a8dbfab982f0da0bc6c2dc2
Author: Jean-Marc Valin <jean-marc.valin@usherbrooke.ca>
Date:   Thu Feb 19 07:35:24 2009 -0500

    Better handling of the "theta bits" and disabling the orthogonalize()

commit 7aa82c694967afa85dd30be8cc670663f98829fe
Author: Jean-Marc Valin <jean-marc.valin@usherbrooke.ca>
Date:   Wed Feb 18 08:01:07 2009 -0500

    tuning the new stereo

commit c2b780a773de66fd9613c7cd54c09b705fe9ce45
Author: Jean-Marc Valin <jean-marc.valin@usherbrooke.ca>
Date:   Sun Feb 15 22:24:52 2009 -0500

    The new stereo coupling actually decodes properly now.

commit 85513c203d773bebcf0a6055f953170d563d890c
Author: Jean-Marc Valin <jean-marc.valin@usherbrooke.ca>
Date:   Sun Feb 15 21:31:16 2009 -0500

    First attempt at a new "constrained" MS stereo scheme

the time-domain representation from Q14 to Q12 (Q29 to Q27 using the
standard convention).

need to iterate at least once.

32-bit muls.

find_spectral_pitch instead of using celt_rcp(celt_sqrt(x))

remove unnecessary copying and some conditional branches.

to assume denominator is positive.

(and fix for celt_div with 16-bit numerator on a 16-bit CPU)

to prevent surprises. Also, a few comments.