The Ut video format uses Huffman trees which are only implicitly coded
in the bitstream: Only the lengths of the codes are coded, the rest has
to be inferred by the decoder according to the rule that the longer
codes are to the left of shorter codes in the tree and on each level the
symbols are descending from left to right.
Because longer codes are to the left of shorter codes, one needs to know
how many non-leaf nodes there are on each level in order to know the
code of the next left-most leaf (which belongs to the highest symbol on
that level). The current code does this by sorting the entries to be
ascending according to length and (for entries with the same length)
ascending according to their symbols. This array is then traversed in
reverse order, so that the lowest level is dealt with first, so that the
number of non-leaf nodes of the next higher level is known when
processing said level.
But this can also be calculated without sorting: Simply count how many
leaf nodes there are on each level. Then one can calculate the number of
non-leaf nodes on each level iteratively from the lowest level upwards:
It is just half the number of nodes of the level below.
This improves performance: For the sample from ticket #4044 the amount
of decicycles for one call to build_huff() decreased from 1055489 to
446310 for Clang 10 and from 1080306 to 535155 for GCC 9.
Reviewed-by: Paul B Mahol <onemda@gmail.com>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
The Ut Video format stores Huffman tables in its bitstream by coding
the length of a given symbol; it does not code the actual code directly,
instead this is to be inferred by the rule that a symbol is to the left
of every shorter symbol in the Huffman tree and that for symbols of the
same length the symbol is descending from left to right. With one
exception, this is also what our de- and encoder did.
The exception only matters when there are codes of length 32, because
in this case the first symbol of this length did not get the code 0,
but 1; this is tantamount to pretending that there is a (nonexistent)
leaf of length 32. This is simply false. The reference software agrees
with this [1].
[1]: 2700a471a7/utv_core/HuffmanCode.cpp (L280)
Reviewed-by: Paul B Mahol <onemda@gmail.com>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
Fixes: signed integer overflow: 2147483594 + 142 cannot be represented in type 'int'
Fixes: 20492/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_UTVIDEO_fuzzer-5658568101724160
Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
This avoids mixing 8bit variants with pro and 10bit with non pro mode.
Fixes: out of array read
Fixes: poc_03_30.avi
Found-by: GwanYeong Kim <gy741.kim@gmail.com>
Reviewed-by: Paul B Mahol <onemda@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
* commit '7c25523cc8':
utvideodec: Fix decoding odd sizes with interlaced video with some formats
See 9ef21a897c
Merged-by: James Almer <jamrial@gmail.com>
0.5% faster loop
Reviewed-by: Paul B Mahol <onemda@gmail.com>
Reviewed-by: Steven Liu <lingjiujianke@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
This is not needed when the buffer is large enough for the worst case of a line
2% faster vlc reading
Reviewed-by: Paul B Mahol <onemda@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
This is actually internal utvideo format.
Allows to make use of SIMD for median prediction for rgb(a) formats,
thus speeding up decoding.
Simplifies code, eases further developement and maintenance.
Update FATE because of pixel format switch.
Signed-off-by: Paul B Mahol <onemda@gmail.com>
Doing slice_end - slice_start is unsafe and can lead to undefined behavior
until slice_end has been properly sanitized.
Reviewed-by: Ronald S. Bultje <rsbultje@gmail.com>
Signed-off-by: Ganesh Ajjanagadde <gajjanag@gmail.com>
Signed-off-by: Luca Barbato <lu_zero@gentoo.org>
Doing slice_end - slice_start is unsafe and can lead to undefined behavior
until slice_end has been properly sanitized.
Reviewed-by: Ronald S. Bultje <rsbultje@gmail.com>
Signed-off-by: Ganesh Ajjanagadde <gajjanag@gmail.com>
