[FFmpeg-trac] #1854(swscale:new): libswscale has unreasonable alignment constraints
FFmpeg
trac at avcodec.org
Sat Oct 27 13:51:07 CEST 2012
#1854: libswscale has unreasonable alignment constraints
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Reporter: gjdfgh | Type: enhancement
Status: new | Priority: normal
Component: swscale | Version: unspecified
Keywords: | Blocked By:
Blocking: | Reproduced by developer: 0
Analyzed by developer: 0 |
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First of, there's a difference between alignment of single pixels, and
alignment of the image start pointer. It's reasonable to demand strict
alignment constraints on single pixels, e.g. that a pixels of size 4
should be aligned to 4.
But having a 16 byte alignment on a pixel start pointer is not reasonable.
For example, this doesn't allow passing cropped images to libswscale.
(Unless the images are cropped in a way they satisfy the alignment
constraints again.)
Rather than fully reverting to the slow path in this case, libswscale
should use the slow path only for the first N unaligned pixels, until an
aligned pixel is reached, and then continue with an accelerated SIMD code
path.
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Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/1854>
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