Given that the AVCodec.next pointer has now been removed, most of the
AVCodecs are not modified at all any more and can therefore be made
const (as this patch does); the only exceptions are the very few codecs
for external libraries that have a init_static_data callback.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
Signed-off-by: James Almer <jamrial@gmail.com>
The Huffman trees used by Ut Video have two important characteristics:
(i) Longer codes are on the left of the tree and (ii) for codes of the
same length, the symbol is descending from left to right in the tree.
Therefore all the information that needs to be transmitted is how long
the code corresponding to a given symbol is; and this is also all that
is transmitted.
Before 341914495e, the decoder used qsort
to sort the (length, symbol) pairs by ascending length and for equal
lengths by ascending symbol. Since said commit, the decoder uses
a first pass over the lengths table to count how many symbols of each
length there are; with (i) one can then easily calculate the code of
the left-most code with a given length in the tree and from there one
can calculate the codes for all entries, using one running counter for
each possible length. This eliminated the explicit qsort in
build_huff().
Yet ff_init_vlc_sparse() sorts the table itself as it has to ensure that
all the entries that will be placed in the same subtable are contiguous.
The tables created now are non-contiguous (they are ordered by symbol
and codes of different length aren't ordered at all; only codes of the
same length are ordered according to (ii)).
This commit therefore modifies the algorithm used to automatically create
tables whose codes are sorted from left to right in the tree. The key to
do so is the observation that the counts obtained in the first pass can
be used to contain the range of the codes of each length in the second
pass: If counts[i] is the count of codes with length i, then the first
counts[32] codes are of length 32, the next counts[31] codes are of
length 31 etc. So one knows the index of the lowest symbol whose code
has length 32 (if any): It is counts[32] - 1 due to (ii), whereas the
index of the lowest symbol whose code has length 31 (if any) is
counts[32] + counts[31] - 1; the index of the second-to-lowest symbol of
length 32 (if existing) is counts[32] - 2 etc.
If one follows the algorithm outlined above, one can switch to
ff_init_vlc_from_lengths() which has no implicit qsort; it also means
that one can offload the computation of the codes.
This turned out to be beneficial for performance: For the sample from
ticket #4044 it decreased the decicycles spent on one call to
build_huff() from 508480 to 340688 (GCC 9.3, looping 10 times over the
file to get enough runs and then repeating this ten times); for another
sample (YUV420p, natural content, 5500 frames, also ten iterations)
the time went down from 382346 to 275533 decicycles.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
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>
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>
Andreas Rheinhardt
Michael Niedermayer
Paul B Mahol
Martin Vignali
Luca Barbato
Ganesh Ajjanagadde
Martin Storsjö
Derek Buitenhuis
Diego Biurrun
James Almer
Alexandra Hájková