[Ffmpeg-devel] [PATCH]: Too much alignment assumed by H264 decoder

Ivan Kalvachev ikalvachev
Thu Dec 22 19:11:56 CET 2005

2005/12/22, Mike Melanson <mike at multimedia.cx>:
> David S. Miller wrote:
> > These uint64_t cast memory operations cause unaligned accesses on
> > platforms such as Sparc, there really isn't anything in the
> > datastructures to ensure this level of alignment.
> >
> > But uint32_t seems to work fine, as the following patch against
> > current CVS implements.
>         Wait... run that by me again: 8-byte alignment causes crashes but
> 4-byte alignment is okay? I hope I don't have to point out that this
> doesn't make much sense. Or are you saying that the compiler you are
> using on Sparc does not support 8-byte alignment and so the data
> structure is being aligned on a random boundary?
>         I must contend that if something in FFmpeg is aligned on an 8-byte
> boundary, it it probably that way for a good reason. One such reason is
> SIMD operations.

Hum.. how about using memset instead of this manual filling?
I'm sure it would be trivial to write an SIMD optimized memset.
We need it in few other places (e.g. better than dsp.clear_blocks)

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