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Mathis Rosenhauer
libaec
Commits
860ce5b5
Commit
860ce5b5
authored
Sep 22, 2012
by
Mathis Rosenhauer
Committed by
Thomas Jahns
Feb 19, 2013
Browse files
restructured splitting
parent
ada39619
Changes
2
Hide whitespace changes
Inline
Sidebyside
src/encode.c
View file @
860ce5b5
...
...
@@ 343,83 +343,106 @@ static uint64_t block_fs(struct aec_stream *strm, int k)
static
int
count_splitting_option
(
struct
aec_stream
*
strm
)
{
int
i
,
k
,
this_bs
,
looked_bothways
,
direction
;
uint64_t
len
,
len_min
,
fs_len
;
/**
Find the best point for splitting samples in a block.
In Rice coding each sample in a block of samples is split at
the same position into k LSB and bit_per_sample  k MSB. The
LSB part is left binary and the MSB part is coded as a
fundamental sequence a.k.a. unary (see CCSDS 121.0B2). The
function of the length of the Coded Data Set (CDS) depending on
k has exactly one minimum (see A. Kiely, IPN Progress Report
42159).
To find that minimum with only a few costly evaluations of the
CDS length, we start with the k of the previous CDS. K is
increased and the CDS length evaluated. If the CDS length gets
smaller, then we are moving towards the minimum. If the length
increases, then the minimum will be found with smaller k. Two
additional checks are used to speed up the process:
1. If we are increasing k to find the minimum then we know that
k+1 will at most eliminate the FS part. OTOH we gain block_size
bits in length through the increased binary part. So if the FS
lenth is already less than the block size then the length of
the CDS for k+1 will be larger than for k. The same can be done
for decreasing k.
2. If 1. is not the case then we have to continue looking. The
next step would be to increase k by one and evaluate the CDS
length. A lower limit for the k+1 FS length is
0.5*(FS_lenblock_size). If half of that is more than
block_size then we can skip k+1 altogether. This reduces to the
condition:
if (fs_len > 5 * block_size)
k++;
We can be repeat this step while the condition is met to skip
several k.
*/
int
k
,
k_min
;
int
this_bs
;
/* Block size of current block */
int
min_dir
;
/* 1 if we saw a decrease in CDS length */
int
dir
;
/* Direction, 1 means increasing k, 0 decreasing k */
uint64_t
len
;
/* CDS length for current k */
uint64_t
len_min
;
/* CDS length minimum so far */
uint64_t
fs_len
;
/* Length of FS part (not including 1s) */
struct
internal_state
*
state
=
strm
>
state
;
this_bs
=
strm
>
block_size

state
>
ref
;
len_min
=
UINT64_MAX
;
i
=
k
=
state
>
k
;
dir
ection
=
1
;
looked_bothways
=
0
;
k
=
k
_min
=
state
>
k
;
dir
=
1
;
min_dir
=
0
;
/* Starting with splitting position of last block. Look left and
* possibly right to find new minimum.
*/
for
(;;)
{
fs_len
=
block_fs
(
strm
,
i
);
len
=
fs_len
+
this_bs
*
(
i
+
1
);
fs_len
=
block_fs
(
strm
,
k
);
len
=
fs_len
+
this_bs
*
(
k
+
1
);
if
(
len
<
len_min
)
{
if
(
len_min
<
UINT64_MAX
)
{
/* We are moving towards the minimum so it cant be in
* the other direction.
*/
looked_bothways
=
1
;
}
if
(
len_min
<
UINT64_MAX
)
min_dir
=
1
;
len_min
=
len
;
k
=
i
;
k
_min
=
k
;
if
(
dir
ection
==
1
)
{
if
(
dir
)
{
if
(
fs_len
<
this_bs
)
{
/* Next can't get better because what we lose by
* additional uncompressed bits isn't compensated
* by a smaller FS part. Vice versa if we are
* coming from the other direction.
*/
if
(
looked_bothways
)
{
break
;
}
else
{
direction
=

direction
;
looked_bothways
=
1
;
i
=
state
>
k
;
}
goto
reverse
;
}
else
{
while
(
fs_len
>
5
*
this_bs
)
{
i
++
;
k
++
;
fs_len
/=
5
;
}
}
}
else
if
(
fs_len
>
this_bs
)
{
/* Since we started looking the other way there is no
* need to turn back.
*/
break
;
}
}
else
{
/* Stop looking for better option if we don't see any
* improvement.
*/
if
(
looked_bothways
)
{
break
;
if
(
k
>=
state
>
kmax
)
goto
reverse
;
else
k
++
;
}
else
{
direction
=

direction
;
looked_bothways
=
1
;
i
=
state
>
k
;
if
(
fs_len
>=
this_bs

k
==
0
)
break
;
k

;
}
}
else
{
goto
reverse
;
}
if
(
i
+
direction
<
0

i
+
direction
>=
strm
>
bit_per_sample

2
)
{
if
(
looked_bothways
)
break
;
direction
=

direction
;
looked_bothways
=
1
;
i
=
state
>
k
;
}
i
+=
direction
;
continue
;
reverse:
if
(
min_dir

state
>
k
==
0
)
break
;
k
=
state
>
k

1
;
dir
=
0
;
min_dir
=
1
;
}
state
>
k
=
k
;
state
>
k
=
k
_min
;
return
len_min
;
}
...
...
@@ 678,6 +701,8 @@ int aec_encode_init(struct aec_stream *strm)
state
>
preprocess
=
preprocess_unsigned
;
}
state
>
kmax
=
(
1U
<<
state
>
id_len
)

3
;
state
>
block_buf
=
(
uint32_t
*
)
malloc
(
strm
>
rsi
*
strm
>
block_size
*
sizeof
(
uint32_t
));
...
...
src/encode.h
View file @
860ce5b5
...
...
@@ 22,7 +22,7 @@ struct internal_state {
int64_t
xmin
;
/* minimum integer for preprocessing */
int64_t
xmax
;
/* maximum integer for preprocessing */
int
i
;
/* counter */
uint32_t
*
block_buf
;
/* RSI blocks of input */
uint32_t
*
block_buf
;
/* RSI blocks of input */
int
blocks_avail
;
/* remaining blocks in buffer */
uint32_t
*
block_p
;
/* pointer to current block */
int
block_len
;
/* input block length in byte */
...
...
@@ 30,15 +30,18 @@ struct internal_state {
int
cds_len
;
/* max cds length in byte */
uint8_t
*
cds_p
;
/* pointer to current output */
int
direct_out
;
/* output to strm>next_out (1)
or cds_buf (0) */
int
bit_p
;
/* bit pointer to the next unused bit in accumulator */
int
ref
;
/* length of reference sample in current block
i.e. 0 or 1 depending on whether the block has
a reference sample or not */
* or cds_buf (0) */
int
bit_p
;
/* bit pointer to the next unused bit in
* accumulator */
int
ref
;
/* length of reference sample in current
* block i.e. 0 or 1 depending on whether
* the block has a reference sample or
* not */
int
zero_ref
;
/* current zero block has a reference sample */
int64_t
zero_ref_sample
;
/* reference sample of zero block */
int
zero_blocks
;
/* number of contiguous zero blocks */
int
k
;
/* splitting position */
int
kmax
;
int
flush
;
/* flush option copied from argument */
};
...
...
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