An operation list containing multiple filter passes, or containing nontrivial
operations before a filter pass, need to be split up into multiple execution
steps with temporary buffers in between; at least for CPU backends.
This helper function introduces the necessary subpass splitting logic
Sponsored-by: Sovereign Tech Fund
Signed-off-by: Niklas Haas <git@haasn.dev>
This code is self-contained and logically distinct from the ops-related
helpers in ops.c, so it belongs in its own file.
Purely cosmetic; no functional change.
Sponsored-by: Sovereign Tech Fund
Signed-off-by: Niklas Haas <git@haasn.dev>
AVFrame just really doesn't have the semantics we want. However, there a
tangible benefit to having SwsFrame act as a carbon copy of a (subset of)
AVFrame.
This partially reverts commit 67f3627267.
Sponsored-by: Sovereign Tech Fund
Signed-off-by: Niklas Haas <git@haasn.dev>
Restructure the loop slightly to avoid UB in the first loop iteration if
src is 4 bytes, which otherwise computes (0 << 32) | 1. Instead, make
1 the default base case and only shift+add if src < dst.
Add an explicit check to preserve the behavior of returnin 0 if src > dst.
This function was assuming that the bits are MSB-aligned, but they are
LSB-aligned in both practice (and in the actual backend).
Also update the documentation of SwsPackOp to make this clearer.
Fixes an incorrect omission of a clamp after decoding e.g. rgb4, since
the max value range was incorrectly determined as 0 as a result of unpacking
the MSB bits instead of the LSB bits:
bgr4 -> gray:
[ u8 XXXX -> +XXX] SWS_OP_READ : 1 elem(s) packed >> 1
[ u8 .XXX -> +++X] SWS_OP_UNPACK : {1 2 1 0}
[ u8 ...X -> +++X] SWS_OP_SWIZZLE : 2103
[ u8 ...X -> +++X] SWS_OP_CONVERT : u8 -> f32
[f32 ...X -> .++X] SWS_OP_LINEAR : dot3 [...]
[f32 .XXX -> .++X] SWS_OP_DITHER : 16x16 matrix + {0 3 2 5}
+ [f32 .XXX -> .++X] SWS_OP_MIN : x <= {255 _ _ _}
[f32 .XXX -> +++X] SWS_OP_CONVERT : f32 -> u8
[ u8 .XXX -> +++X] SWS_OP_WRITE : 1 elem(s) planar >> 0
(X = unused, + = exact, 0 = zero)
This can turn any compatible sequence of operations into a single packed
shuffle, including packed swizzling, grayscale->RGB conversion, endianness
swapping, RGB bit depth conversions, rgb24->rgb0 alpha clearing and more.
This handles the low-level execution of an op list, and integration into
the SwsGraph infrastructure. To handle frames with insufficient padding in
the stride (or a width smaller than one block size), we use a fallback loop
that pads the last column of pixels using `memcpy` into an appropriately
sized buffer.
See docs/swscale-v2.txt for an in-depth introduction to the new approach.
This commit merely introduces the ops definitions and boilerplate functions.
The subsequent commits will flesh out the underlying implementation.
