Hi,
I wonder if there are strict requirements for alignment of AVFrame
buffers. Yes, it is usually aligned by default, but there are filters,
like crop or pad which tries to avoid copying data even at the cost of
breaking the alignment. This unfortunately causes crashes for code which
requires it, some examples:
- the zscale filter only checks input buffer alignment but not output
buffer alignment, therefore might crash if a later pad filter provides
an unaligned get_buffer callback for a filter chain.
- the blend/tblend filter has a similar problem, it's ASM code is using
aligned movs for output. (not for input however).
- the dnxhd encoder depends on aligment of its input buffers.
How this should be fixed?
- Change pad/crop filters to only do "smart" pad/crop if alignment can be
guaranteed? Maybe a user option should be added to enable "unsafe" mode?
- Add checks for aligment where it is actually required, e.g. in dnxhd
encoder or blend/zscale filter?
- Change blend code to use unaligned movs even for output?
Thanks,
Marton
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