We now encode the highest bitrate part of the split first and transfer
any unused bits to the other part. We use a dead zone of three bits
to prevent redistributing in cases of random fluctuation (or else
we will statistically lower the allocation of higher frequencies at
low-mid bitrates).

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.

Also defining a 1-byte packet as triggering the PLC/CNG

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

This changes folding so that the LCG is never used on transients
 (either short blocks or long blocks with increased time
 resolution), except in the case that there's not enough decoded
 spectrum to fold yet.

It also now only subtracts the anti-collapse bit from the total
 allocation in quant_all_bands() when space has actually been
 reserved for it.

Finally, it cleans up some of the fill and collapse_mask tracking
 (this tracking was originally made intentionally sloppy to save
 work, but then converted to replace the existing fill flag at the
 last minute, which can have a number of logical implications).
The changes, in particular:
1) Splits of less than a block now correctly mark the second half
    as filled only if the whole block was filled (previously it
    would also mark it filled if the next block was filled).
2) Splits of less than a block now correctly mark a block as
    un-collapsed if either half was un-collapsed, instead of marking
    the next block as un-collapsed when the high half was.
3) The N=2 stereo special case now keeps its fill mask even when
    itheta==16384; previously this would have gotten cleared,
    despite the fact that we fold into the side in this case.
4) The test against fill for folding now only considers the bits
    corresponding to the current set of blocks.
   Previously it would still fold if any later block was filled.
5) The collapse mask used for the LCG fold data is now correctly
    initialized when B=16 on platforms with a 16-bit int.
6) The high bits on a collapse mask are now cleared after the TF
    resolution changes and interleaving at level 0, instead of
    waiting until the very end.
   This prevents extraneous high flags set on mid from being mixed
    into the side flags for mid-side stereo.

The initialiser already takes care of this

Using the min energy of the two last non-transient frames rather
than the min of just the two last frames. Also slightly increasing
the "thresh" upper bound coefficient to 0.5.

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

By moving the energy floor to the encoder, we can use a different
floor for prediction than for the decay level. Also, the fixed-point
dynamic range has been increased to avoid overflows when a fixed-point
decoder is used on a stream encoded in floating-point.

If someone messed up scaling, they'll know because it'll sound bad

The most important thing is to not screw up the energy. Then we
compare the bit-rates.

This was computing on uninitialized data (though the result was never
used)

Gregory Maxwell authored 14 years ago and Jean-Marc Valin committed 14 years ago

Correct an encoder/decoder mismatch at low volume levels. Relax some low level clamps so that the dynamic range can extend further below the 16bit floor.

Also a fix for the zero-ing of unused band energies.

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

We were always storing collapse_masks[i*C+1], which could have
 overflowed the buffer on the last band in mono.
This also moves the stores outside the conditional, which allows
 common code to be used for masking the high bits, address
 generation, etc.

This provides more entropy and allows some more flexibility on the
encoder side.

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

Jean-Marc's original anti-collapse patch used a threshold on the
 content of a decoded band to determine whether or not it should
 be filled with random noise.
Since this is highly sensitive to the accuracy of the
 implementation, it could lead to significant decoder output
 differences even if decoding error up to that point was relatively
 small.

This patch detects collapsed bands from the output of the vector
 quantizer, using exact integer arithmetic.
It makes two simplifying assumptions:
 a) If either input to haar1() is non-zero during TF resolution
     adjustments, then the output will be non-zero.
 b) If the content of a block is non-zero in any of the bands that
     are used for folding, then the folded output will be non-zero.
b) in particular is likely to be false when SPREAD_NONE is used.
It also ignores the case where mid and side are orthogonal in
 stereo_merge, but this is relatively unlikely.
This misses just over 3% of the cases that Jean-Marc's anti-collapse
 detection strategy would catch, but does not mis-classify any (all
 detected collapses are true collapses).

This patch overloads the "fill" parameter to mark which blocks have
 non-zero content for folding.
As a consequence, if a set of blocks on one side of a split has
 collapsed, _no_ folding is done: the result would be zero anyway,
 except for short blocks with SPREAD_AGGRESSIVE that are split down
 to a single block, but a) that means a lot of bits were available
 so a collapse is unlikely and b) anti-collapse can fill the block
 anyway, if it's used.
This also means that if itheta==0 or itheta==16384, we no longer
 fold at all on that side (even with long blocks), since we'd be
 multiplying the result by zero anyway.

This looks for bands in each short block that have no energy. For
each of these "collapsed" bands, noise is injected to have an
energy equal to the minimum of the two previous frames for that band.
The mechanism can be used whenever there are 4 or more MDCTs (otherwise
no complete collapse is possible) and is signalled with one bit just
before the final fine energy bits.