c1c40a76c2
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.
158 lines
4.5 KiB
C
158 lines
4.5 KiB
C
/* Copyright (c) 2007 CSIRO
|
|
Copyright (c) 2007-2009 Xiph.Org Foundation
|
|
Written by Jean-Marc Valin */
|
|
/*
|
|
Redistribution and use in source and binary forms, with or without
|
|
modification, are permitted provided that the following conditions
|
|
are met:
|
|
|
|
- Redistributions of source code must retain the above copyright
|
|
notice, this list of conditions and the following disclaimer.
|
|
|
|
- Redistributions in binary form must reproduce the above copyright
|
|
notice, this list of conditions and the following disclaimer in the
|
|
documentation and/or other materials provided with the distribution.
|
|
|
|
- Neither the name of the Xiph.org Foundation nor the names of its
|
|
contributors may be used to endorse or promote products derived from
|
|
this software without specific prior written permission.
|
|
|
|
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
|
|
``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
|
|
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
|
|
A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR
|
|
CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
|
|
EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
|
|
PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
|
|
PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
|
|
LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
|
|
NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
|
|
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
|
|
*/
|
|
|
|
#ifdef HAVE_CONFIG_H
|
|
#include "config.h"
|
|
#endif
|
|
|
|
#include "laplace.h"
|
|
#include "mathops.h"
|
|
|
|
/* The minimum probability of an energy delta (out of 32768). */
|
|
#define LAPLACE_LOG_MINP (0)
|
|
#define LAPLACE_MINP (1<<LAPLACE_LOG_MINP)
|
|
/* The minimum number of guaranteed representable energy deltas (in one
|
|
direction). */
|
|
#define LAPLACE_NMIN (16)
|
|
|
|
int ec_laplace_get_start_freq(int decay)
|
|
{
|
|
celt_uint32 ft = 32768 - LAPLACE_MINP*(2*LAPLACE_NMIN+1);
|
|
int fs = (ft*(16384-decay))/(16384+decay);
|
|
return fs+LAPLACE_MINP;
|
|
}
|
|
|
|
static int ec_laplace_get_freq1(int fs0, int decay)
|
|
{
|
|
celt_int32 ft;
|
|
ft = 32768 - LAPLACE_MINP*(2*LAPLACE_NMIN) - fs0;
|
|
return ft*(16384-decay)>>15;
|
|
}
|
|
|
|
void ec_laplace_encode_start(ec_enc *enc, int *value, int decay, int fs)
|
|
{
|
|
unsigned fl;
|
|
int val = *value;
|
|
fl = 0;
|
|
if (val)
|
|
{
|
|
int s;
|
|
int i;
|
|
s = -(val<0);
|
|
val = val+s^s;
|
|
fl = fs;
|
|
fs = ec_laplace_get_freq1(fs, decay);
|
|
/* Search the decaying part of the PDF.*/
|
|
for (i=1; fs > 0 && i < val; i++)
|
|
{
|
|
fs *= 2;
|
|
fl += fs+2*LAPLACE_MINP;
|
|
fs = (fs*(celt_int32)decay)>>15;
|
|
}
|
|
/* Everything beyond that has probability LAPLACE_MINP. */
|
|
if (fs <= 0)
|
|
{
|
|
int di;
|
|
int di_max;
|
|
di_max = (32768-fl+LAPLACE_MINP-1)>>LAPLACE_LOG_MINP;
|
|
di_max = (di_max-s)>>1;
|
|
di = IMIN(val - i, di_max);
|
|
fl += (2*di+1+s)*LAPLACE_MINP;
|
|
fs = IMIN(LAPLACE_MINP, 32768-fl);
|
|
*value = i+di+s^s;
|
|
}
|
|
else
|
|
{
|
|
fs += LAPLACE_MINP;
|
|
fl += fs&~s;
|
|
}
|
|
celt_assert(fl+fs<=32768);
|
|
celt_assert(fs>0);
|
|
}
|
|
ec_encode_bin(enc, fl, fl+fs, 15);
|
|
}
|
|
|
|
|
|
void ec_laplace_encode(ec_enc *enc, int *value, int decay)
|
|
{
|
|
int fs = ec_laplace_get_start_freq(decay);
|
|
ec_laplace_encode_start(enc, value, decay, fs);
|
|
}
|
|
|
|
|
|
int ec_laplace_decode_start(ec_dec *dec, int decay, int fs)
|
|
{
|
|
int val=0;
|
|
unsigned fl;
|
|
int fm;
|
|
fm = ec_decode_bin(dec, 15);
|
|
fl = 0;
|
|
if (fm >= fs)
|
|
{
|
|
val++;
|
|
fl = fs;
|
|
fs = ec_laplace_get_freq1(fs, decay)+LAPLACE_MINP;
|
|
/* Search the decaying part of the PDF.*/
|
|
while(fs > LAPLACE_MINP && fm >= fl+2*fs)
|
|
{
|
|
fs *= 2;
|
|
fl += fs;
|
|
fs = ((fs-2*LAPLACE_MINP)*(celt_int32)decay)>>15;
|
|
fs += LAPLACE_MINP;
|
|
val++;
|
|
}
|
|
/* Everything beyond that has probability LAPLACE_MINP. */
|
|
if (fs <= LAPLACE_MINP)
|
|
{
|
|
int di;
|
|
di = (fm-fl)>>(LAPLACE_LOG_MINP+1);
|
|
val += di;
|
|
fl += 2*di*LAPLACE_MINP;
|
|
}
|
|
if (fm < fl+fs)
|
|
val = -val;
|
|
else
|
|
fl += fs;
|
|
}
|
|
celt_assert(fl<32768);
|
|
celt_assert(fs>0);
|
|
celt_assert(fl<=fm);
|
|
celt_assert(fm<IMIN(fl+fs,32768));
|
|
ec_dec_update(dec, fl, IMIN(fl+fs,32768), 32768);
|
|
return val;
|
|
}
|
|
|
|
int ec_laplace_decode(ec_dec *dec, int decay)
|
|
{
|
|
int fs = ec_laplace_get_start_freq(decay);
|
|
return ec_laplace_decode_start(dec, decay, fs);
|
|
}
|