[FFmpeg-devel] [PATCH] increase alignment for DCT block arrays to 16
Tue Apr 8 03:09:54 CEST 2008
On 05/04/2008, Michael Niedermayer <michaelni at gmx.at> wrote:
> On Fri, Apr 04, 2008 at 08:56:34PM -0400, Alexander Strange wrote:
> > Some decoders (MJPEG, WMV2) have their DCT block arrays aligned to 8 bytes,
> > which causes obvious problems with an SSE2 IDCT. Either one of the attached
> > patches fixes it; I wasn't sure if there would be problems with the first
> > method, so I did it two ways.
> > Method 1 - As with Altivec/MMI, redefine DECLARE_ALIGNED_8 and STRIDE_ALIGN
> > to be 16. This has some other nice properties, since I won't have to assume
> > picture pointers are only 8-byte aligned outside ffmpeg. It also means that
> > nobody else can introduce a new decoder and have it break under SSE2.
> > Method 2 - Just change the problematic DECLARE_ALIGNED_8 to _16.
> Method 2.
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