Disadvantage is that it no longer allows modifying brightness through
adjustment of the RGB lookup table. Advantage is that now monowhite/black
no longer need to be identified as a RGB format.
This fixes some cases where the clipping was entirely missing.
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
Thanks (for the comments and review) -to: Reimar, beastd, Ronald
This reverts commit 77d88b872d.
The revert fixes actual overflows and a segfault as the variables
are signed and can be negative.
Conflicts:
libswscale/swscale.c
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
This fixes integer multiplication overflows in RGB48 output
(vertical) scaling as detected by IOC. What happens is that for
certain types of filters (lanczos, spline, bicubic), the
intermediate sum of coefficients in the middle of a filter can
be larger than the fixed-point equivalent of 1.0, even if the
final sum is 1.0. This is fine and we support that.
However, at frame edges, initFilter() will merge the coefficients
for the off-screen pixels into the top or bottom pixel, such as
to emulate edge extension. This means that suddenly, a single
coefficient can be larger than the fixed-point equivalent of
1.0, which the vertical scaling routines do not support.
Therefore, remove the merging of coefficients for edges for
the vertical scaling filter, and instead add edge detection
to the scaler itself so that it copies the pointers (not data)
for the edges (i.e. it uses line[0] for line[-1] as well), so
that a single coefficient is never larger than the fixed-point
equivalent of 1.0.
This fixes the same overflow as in the RGB48/16-bit YUV scaling;
some filters can overflow both negatively and positively (e.g.
spline/lanczos), so we bias a signed integer so it's "half signed"
and "half unsigned", and can cover overflows in both directions
while maintaining full 31-bit depth.
Signed-off-by: Mans Rullgard <mans@mansr.com>
We're shifting individual components (8-bit, unsigned) left by 24,
so making them unsigned should give the same results without the
overflow.
Signed-off-by: Ronald S. Bultje <rsbultje@gmail.com>
For certain types of filters where the intermediate sum of coefficients
can go above the fixed-point equivalent of 1.0 in the middle of a filter,
the sum of a 31-bit calculation can overflow in both directions and can
thus not be represented in a 32-bit signed or unsigned integer. To work
around this, we subtract 0x40000000 from a signed integer base, so that
we're halfway signed/unsigned, which makes it fit even if it overflows.
After the filter finishes, we add the scaled bias back after a shift.
We use the same trick for 16-bit bpc YUV output routines.
Signed-off-by: Mans Rullgard <mans@mansr.com>
libswscale/swscale.c:2744:40: warning: to be safe all intermediate pointers in cast from ‘int16_t **’ to ‘const int16_t **’ must be ‘const’ qualified [-Wcast-qual]
libswscale/swscale.c:2745:41: warning: to be safe all intermediate pointers in cast from ‘int16_t **’ to ‘const int16_t **’ must be ‘const’ qualified [-Wcast-qual]
libswscale/swscale.c:2746:41: warning: to be safe all intermediate pointers in cast from ‘int16_t **’ to ‘const int16_t **’ must be ‘const’ qualified [-Wcast-qual]
libswscale/swscale.c:2747:78: warning: to be safe all intermediate pointers in cast from ‘int16_t **’ to ‘const int16_t **’ must be ‘const’ qualified [-Wcast-qual]
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
As old bits are shifted out of the accumulator, they cause signed
overflows when they reach the end. Making the variable unsigned fixes
this.
Signed-off-by: Mans Rullgard <mans@mansr.com>
Ronald S. Bultje
Michael Niedermayer
Diego Biurrun
Paul B Mahol
Mans Rullgard
Kieran Kunhya